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NRC Internal Guideline – Timber Procurement & Specifications // December 2006 // J Fowler & J Ashmore // www.nrc.no section 1 - introduction

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NRC Internal Guideline – Timber Procurement and Specifications

1 Introduction

1.1 Overview and contents

This booklet is a guideline for NRC staff involved in the procurement of timber in the context of humanitarian emergencies.

1.1.1 Contents

1 Introduction..................................................................................... 1 1.1 Overview and contents .................................................................. 1 1.2 Booklet scope............................................................................... 2 1.3 Audience ..................................................................................... 2 1.4 What is special about procuring timber? ........................................... 2

2 Timber – the basics........................................................................... 4 2.1 The parts of a tree ........................................................................ 4 2.2 Types of timber ............................................................................ 4 2.3 Properties of timber ...................................................................... 6

3 The timber procurement process......................................................... 9 3.1 Needs identification....................................................................... 9 3.2 Budget clearance .......................................................................... 9 3.3 Timber specifications/bills of quantities ............................................ 9 3.4 Tendering – quotes and bids........................................................... 9 3.5 Place order .................................................................................. 10 3.6 Delivery....................................................................................... 10 3.7 Storage ....................................................................................... 11 3.8 Distribution and transport .............................................................. 13

4 Timber specifications in detail............................................................14 4.1 Specifying treatments.................................................................... 15 4.2 Specifying moisture content ........................................................... 18 4.3 Specifying strength grades ............................................................. 18 4.4 Specifying durability...................................................................... 19 4.5 Visual grading .............................................................................. 19 4.6 Specifying quantities and finishing................................................... 22 4.7 Specifying documentation .............................................................. 23

5 Chain of custody and certification.......................................................24 5.1 Definition of chain of custody.......................................................... 24 5.2 Certification – legal or sustainable ................................................... 24

6 Annexes .........................................................................................27 6.1 Glossary of terms.......................................................................... 27 6.2 CITES Appendices for timber .......................................................... 28 6.3 Timber sizes comparison................................................................ 30 6.4 Phytosanitary certificate examples................................................... 31 6.5 Comparison of strength grades ....................................................... 33 6.6 Safe stacking of sawn timber.......................................................... 34 6.7 Container sizes ............................................................................. 37 6.8 Conversion table........................................................................... 38 6.9 Measuring moisture content ........................................................... 39 6.10 Timber treatments requiring expert handling (New Zealand) ............... 40 6.11 FSC certified forests ...................................................................... 41 6.12 References and further reading / resources....................................... 42


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1.1.2 Acknowledgements

This guideline was developed by Jon Fowler and Joseph Ashmore for the Norwegian Refugee Council (NRC). The work draws on, amongst other sources, George Kuru’s various documents for UN-FAO in Indonesia [Kuru (2005)] for which a download link is listed in Annex ‘ 6.12 References and further reading’.

The authors would like to thank the following people for their assistance and information: Simon Armstrong (ConFor); Ralph Ashton (WWF); Tom Bamforth (NRC); Rick Bauer (Oxfam); Gordon Browne (Southampton Solent University); Tom Corsellis (sheltercente.org); Bruno Dercon (UN-Habitat); Elin Holmén; Julia Macro; Peter Manfield; Pat Naidoo (Oxfam); Øyvind Nordlie (NRC); Adrian Porter; Kazuko Puff (UNIDO). Special thanks to UNIDO for reproduction of graphics.

1.2 Booklet scope

This booklet is limited to general guidelines regarding procurement of timber and is intended to be used alongside the NRC Logistics Manual and NRC Shelter Handbook. It aims to assist the reader in dealing with some of the special considerations associated with timber listed below.

This booklet is not intended to promote timber use and, wherever possible, reduced timber construction techniques should be used.

This booklet can not cover all aspects of timber, particularly in terms of the properties of different species of tree or details of international and national standards with regard to timber construction or treatment specifications. As with all guidelines, its recommendations should be adjusted for the local context.

This guide considers the procurement of sawn wood, timber poles and bamboo. Plywood and other timber derivatives are not included.

1.3 Audience

This booklet is intended to be used by NRC logisticians, project and program managers.

1.4 What is special about procuring timber?

Timber is a product that requires some special considerations regarding its procurement. They are as follows:

1.4.1 Timeliness

Importing timber in large quantities can take a long time (e.g. post-Tsunami timber procurement in Indonesia). Lead time can easily reach 3 months for a large operation:

Task Time Total time Needs assessment and specification 2 weeks 2 weeks Tendering and contract negotiation 3 weeks 5 weeks Consolidation of consignment 2 weeks 7 weeks Link to shipping service 2 weeks 9 weeks Shipping to regional then secondary hub 3 weeks 12 weeks Customs & national government requirements 1 week 13 weeks Transport to warehouse 2 days Over 13 weeks

Procurement of timber may present real problems in responding to needs in an emergency. Section ‘ 3 The timber procurement process’ considers this issue in more detail.


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1.4.2 Environmental issues, certification and legality

Emergency situations often have a negative impact on local forests due to increased demand for local timber from organizations and the affected population outstripping sustainable supply, often in areas where environmental problems may have proceeded as disaster. Consider alternative options to timber in all cases.

Even if the timber requirements are not in the magnitude of a full construction program, local deforestation is possible and logisticians and managers need to be aware of where timber comes from (UNHCR (2005) Environmental Guidelines).

An environmentally responsible NGO should procure timber: from a legal source (trade in some tree species either illegal or controlled); from a forest that is managed in a sustainable way; and which has undergone environmentally responsible processes.

A strong quality-control mechanism is required for large procurements of timber requiring expert staff or third-party assessment (see Section ‘ 5 Chain of custody and certification’).

1.4.3 Appropriateness

Principles of the use of appropriate design and materials in construction should be followed (See NRC Shelter Handbook). Also note Sphere Shelter, Settlement and Non-Food Items (chapter 4) standards 4, 5 and 61:

Shelter and settlement standard 4: design

“The design of the shelter is acceptable to the affected population and provides sufficient thermal comfort, fresh air and protection from the climate to ensure their dignity, health, safety and well-being”. (p.221)

Shelter and settlement standard 5: construction

“The construction approach is in accordance with safe local building practices and maximizes local livelihood opportunities”. (p.224)

Shelter and settlement standard 6: environmental impact

“The adverse impact on the environment is minimized by the settling of the disaster-affected households, the material sourcing and construction techniques used”. (p.227)

In following these standards it is essential to consider whether timber should be used at all. Timber specification should preferably involve a timber expert and/or and engineer.

1.4.4 Storage

Timber requires special storage conditions due to its size and the possibility of it being attacked by pests or fungus. Temporary storage can be made outdoors, but the risk of timber becoming wet or infected means that warehousing will be necessary as soon as possible (see Section ‘ 3.7 Storage’ for further details and Annex ‘ 6.6 Safe stacking of sawn timber’ for stacking advice).

1 The Sphere Project (2004).

http://www.unhcr.org/cgi-bin/texis/vtx/protect/opendoc.pdf?tbl=PROTECTION&id=3b03b2a04

http://www.sphereproject.org/

NRC Internal Guideline – Timber Procurement & Specifications // December 2006 // J Fowler & J Ashmore // www.nrc.no section 2 – timber - the basics

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2 Timber – the basics

2.1 The parts of a tree

The trunk of a tree supports the foliage and fruits of the crown and resists tension, compression and bending.

The tree is made up of different cell tissues. Some cells deliver liquids, others store and distribute foods and others provide strength and elasticity.

The heartwood provides the structural strength of the tree and the sapwood, which is normally lighter in color, delivers liquids to the crown. The sapwood is more susceptible to attack by insects and fungi than the heartwood.

The heart of a cut log can be brittle dead tissue, the area around it is sometimes referred to as ‘truewood’.

2.2 Types of timber

2.2.1 Softwood or hardwood

Trees are divided into two types: softwoods and hardwoods. This does not correspond to the hardness of the wood.

Hardwoods are from broad-leaved trees which produce seeds in an enclosed case such as a birch or willow tree and are normally evergreen in the tropics and deciduous (lose their leaves once a year) in temperate zones.

Softwoods come from coniferous trees which produce cones and have leaves like needles such as pine trees and spruces and normally grow in temperate zones. Hardwoods tend to be denser, stronger and grow slower though balsa wood, one of the lightest woods, is actually a hardwood.

A tree has at least two names – a Latin (or ‘botanical’) name and, varying between countries, a common name. As common names vary it is important to be sure of the Latin name of the species required.

2.2.2 Primary or secondary wood

The timber construction industry uses the terms primary and secondary to classify woods. Primary timbers are mostly slow-growing hardwoods which are naturally durable and normally expensive and in short supply. Secondary timbers are fast-growing species whose low natural durability can be improved with seasoning and

Figure 1: Parts of a tree

A= Outer bark (dry) B= Innerbark (alive) C= Heartwood D= Sapwood

E = pith – original stem of tree

Figure 2: Types of tree

hardwood softwood

Tru

nk

Cro

wn

Roots

A B C D

E


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preservatives and are more likely to be used in construction.

2.2.3 Poles or sawn wood

Timber can be procured as poles or as sawn wood. Depending on the situation it may be more appropriate to use timber poles as they may be easier to obtain and more appropriate to local building practices. Poles may be cheaper due to fewer processing costs. Poles are normally procured by quantity and diameter (usually 100mm or 150mm) and are normally around 3-4 meters in length (the diameter may thin towards the end). A good guide to timber pole use is Timber Pole Construction by Jayanetti & Follett (2000).

Poles that are ‘peeled’ or ‘rounded’ (i.e. have their bark stripped to produce an even size) lose 30% of their material and 40% of their strength. Rounded poles may have less strict import condition placed on them than poles with bark.

Timber that has the rings at angles of between 45° and 90° to the wide surface is called quartersawn, and timber with the rings at an angle between 0° and 45° to the wide surface is called plainsawn or backsawn timber. Quartersawn wood is more expensive as it involves turning the timber while sawing and discarding the center. However, quarter sawn wood shrinks and distorts less. NRC is unlikely to carry out any sawing itself and this should be outsourced to a competent company if it is required.

2.2.4 Bamboo

Bamboo is not strictly timber, but is often used as a construction material in parts of Asia and South America and may be useful in the building of temporary structures. It is very versatile and fast-growing, reproducing through its roots, and can be harvested in 3-5 years versus 10-50 years for most soft and hardwoods. Its flexibility can make it a useful building material in earthquake areas.

It is estimated that 1 billion people live in bamboo houses2. However, bamboo may have negative social connotations so it is important to consider the usual construction methods in the area and whether use of bamboo will be accepted by the affected population. It is important that people should be familiar with its application.

Both the season (bamboo should be harvested in the autumn and winter in the sub-tropics and the dry season in the tropics) and the species type are important when procuring bamboo. Bamboo intended for structural works needs to be dried for two–three months after harvest, until about 90 per cent of the water content has dried out. It should be harvested at dawn, when the plant is at its most dry.3

Bamboo can be treated to increase its durability (see Section ‘ 2.3.8 Protection through seasoning/drying wood’ and ‘ 4.1 Specifying treatments’). A good guide to bamboo use is the ITDG publication ‘Building with Bamboo’ by Janssen, J. (1995).

2 http://www.inbar.int/housing/facts.htm 3 Corsellis and Vitale (2005) p.258

Figure 3: Sawing patterns Note shrinkage/warping of timber with different sawing patterns Quartersawn Backsawn


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2.3 Properties of timber

2.3.1 Sawn timber features

The main, flat surface of timber is normally called its ‘face’, the top and bottom are called ‘ends’ while the sides are ‘edges’. The features on a piece of timber are often referred to as its ‘figure’. The whole piece of timber is sometimes known as a ‘board’. The lines seen at the ends are the ‘growth’ or ‘annual’ rings.

The grain normally runs from end-to-end in more or less straight lines. Deviation from this straight line parallel to the edge of the board is measured as the slope of the grain. Knots, old branches embedded in the trees trunk, also affect the smooth-running of the grain.

The features or figure of a board are used to grade the board visually – see Section ‘ 4.5 Visual grading’ for more details.

The principle axes in timber are Longitudinal (where the face meets the edge), Radial (where the face meets the end) and Tangential (where the end meets the edge). Timber is strongest along the longitudinal axis.

2.3.2 Durability

Timber’s durability is measured by its resistance to attacks by insects or fungi. There are two basic means of protecting timber and improving its durability. Firstly, keep the moisture content of timber below around 18%; secondly, treat the timber with a preservative (See Section ‘ 4.1 Specifying treatments’).

Timber’s durability is normally expressed as a class number which varies from country-to-country. See Section ‘ 4.4 Specifying durability’ for further information.

2.3.3 Timber degeneration

There are two main causes of timber degeneration – wood rot and insect pests.

Wood rot is caused when sufficient oxygen, heat and moisture is present for fungi to attack timber. There are two main types of rot:

• ‘Wet’ or ‘White’ rot – the fungi feeds on the cellulose and lignin content of the wood leaving behind a slimy residue.

• ‘Dry’ or ‘Brown’ rot – the fungi only feeds on the cellulose. It leaves a brown residue and the wood is left very soft and cracked

Since oxygen and heat are always present, moisture content remains the controllable factor. Rot is impossible at less than 12% moisture content and possible but not likely between 12-18%.

Insects such as wood-boring beetles, termites wood wasps and carpenter bees and carpenter ants can attack wood. Protection against pests is best achieved by treating the wood and keeping it dry. Imported timber normally requires a phytosanitary certificate to guarantee it is free of pests. Sample phytosanitary certificates are shown in Annex ‘ 6.4 Phytosanitary certificate examples’.

Figure 4: Timber board features

Figure 5: Principle axes in timber L=Longitudinal, R=Radial, T=Tangential

Knot

FACE

END

Growth rings

EDGE

Grain

T

L

R


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2.3.4 Permeability/penetration

The permeability of a timber varies with the species of tree and will determine how easily the timber takes up a preservative or flame retardant treatment. In all timber the sapwood is more permeable than the heartwood.

The permeability or penetration of timber is described by its ‘penetration class’. Classification varies from country to country. See Section ‘ 4.1.3 Penetration classes’ for more info.

2.3.5 Fire resistance

The fire resistance of a tree is mostly determined by its density, though partly by its moisture content. Large sizes of timber are difficult to burn as the charcoal produced on the surface of a timber block acts a protective barrier for the wood below the surface. Fire retardant chemicals can be applied – be sure to follow Health and Safety considerations when using them.

2.3.6 Strength

The strength of timber varies from species to species and is measured in terms of its resistance to compression, tension and shear forces. The strength of timber is closely related to its density.

There are a number of different national and international standards for strength measurement – see Section ‘ 4.3 Specifying strength grades’ for more details.

Density is measured in weight per cubic meter (m) and normally at a moisture content of 12%. The most common density for softwoods used in construction is between 450 and 550 kg/ m. Strength changes dramatically if it is measured with (parallel to) or against (perpendicular to) the grain of the timber.

The main tests for strength are as follows:

Figure 7: Forces used in timber strength tests Shear – forces along or across planes Parallel to grain Perpendicular to grain Rolling 20% of parallel

Tensile strength – pulling forces Parallel to grain Perpendicular to grain

Compression strength – squeezing forces Bending strength Parallel to grain Perpendicular to grain Hanging force

Figure 6: Timber densities (Density of seasoned timber is measured at 12%MC.) Type Density Very light <300 kg/m Light 300-450 kg/m Medium 450-650 kg/m Heavy 650-800 kg/m Very heavy 800+ kg/m


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Strength is normally graded both by machine and visually. A number of different international and national grading classes exist so specification will depend on the country of supply. In the absence of national standards, locally procured timber can be graded visually. Visual strength checks include looking at knots, grain direction, and decay. See Section ‘ 4.5 Visual grading’ for details.

2.3.7 Moisture content and measurement

Over half of a living tree's weight is moisture and when it is freshly cut down it is termed ‘green’. As timber dries after felling, ‘free water’ leaves the wood cell ‘voids’. Once all the cell voids are empty the moisture content reaches about 30–35% MC in hardwoods and 25–30% MC in softwoods (normally expressed as an average of 28%) and, because water is still bound in the cell walls, this point is known as ‘fiber saturation point’.

When the timber is dried below the ‘fiber saturation point’, ‘bound water’ leaves the cell walls and the timber begins to shrink.

Timber that has a moisture content significantly different to the surrounding humidity can warp, swell or split.

Moisture content (MC) is expressed as a percentage of the weight of the moisture timber contains compared to its completely oven dry weight (all possible moisture is lost). The moisture present in wood can weigh more than the dry weight of the wood and therefore it is possible to have a MC of over 100% when it is green. Annex ‘ 6.9 Measuring moisture content’ explains the calculation and describes using electric moisture meters.

2.3.8 Protection through seasoning/drying wood

“Seasoning” is the term used for drying wood in a controlled way to avoid distortion. Seasoned wood is lighter, stronger and less likely to split, warp or rot. There are generally two methods of seasoning wood: air drying and kiln-drying (or ‘forced-air’ drying).

Air-drying reduces moisture content to between 15 and 20% and involves stacking timber so that air can circulate around it. It takes around one year per inch (2.5cm) of thickness of timber for hardwoods and about six months per inch (2.5cm) for softwoods. This method is often used for timber poles.

Kiln-drying involves using heated air to drive out the moisture from timber while steam controls the rate of evaporation to reduce splitting. This method can bring timber moisture content to any desired specification in a few weeks.

Bamboo can be air-dried in stacked frames with good air circulation for 6 - 12 weeks. Kiln-drying of bamboo takes 2 - 3 weeks but some species may not tolerate quick drying.

2.3.9 Shrinkage

Depending on which part of the tree timber is cut from, it will shrink in different directions (see Figure 3: Sawing patterns). The amount of shrinkage will also depend on the species of tree.

Shrinking occurs during the drying of timber or changes in humidity and moisture levels. Timber that is sawn first and then dried will experience more distortion or shrinkage than timber that is dried and then sawn.

Bamboo shrinks more than wood, shrinking 10-16% in cross section and 15-17% in wall thickness.

NRC Internal Guideline – Timber Procurement & Specifications // December 2006 // J Fowler & J Ashmore // www.nrc.no section 3 – the timber procurement process

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3 The timber procurement process

Follow the standard NRC procurement process. Below are additional considerations for timber at each stage of the NRC procurement process:

3.1 Needs identification

When deciding on whether timber is required, consider the following:

• Local building techniques and materials

• Pressure on local forests

• Possibility and appropriateness of other building materials/ techniques

• Whether there are local solutions for repairing or substituting imported timber

In all cases, consider reduced-timber construction methods or whether it is appropriate to use timber at all.

Once design plans for buildings/shelters are agreed, specification of timber in terms of its grade, species and size will depend on4:

1. Performance requirements and structural use of the material

2. Basic strength, stiffness and other engineering attributes.

3. Physical grade characteristics (e.g. knots, splits, etc) that affect its engineering attributes.

4. Natural durability of the timber and the level of hazard it is being exposed to.

5. The standard sizes that are available and whether timber will be pre-sawn or sawn on site.

6. Whether sawn timber or poles/logs are required (import conditions may be different)

Procurement may be for different products which come from different stages in the Chain of Custody (see Section ‘ 5 Chain of custody and certification’). It is important to identify what checks need to be made as checks for non-sawn logs will be different from checks for sawn wood.

3.2 Budget clearance

No additions.

3.3 Timber specifications/bills of quantities

Potential suppliers must understand exactly what you require in terms of species, quality control and certification. See Section ‘ 4 Timber specifications in detail’ for details.

3.4 Tendering – quotes and bids

Tendering should follow the NRC logistics guidelines but should include the detailed timber specifications sheet described in Section ‘ 4 Timber specifications in detail’.

When tendering for timber, consider long-term tenders from multiple suppliers, especially when long lead times are involved. Long-term procurement agreements should improve the delivery process. To minimize delays complete as much paperwork required by customs and other government bodies before the consignment arrives as well as securing sufficient transport.

4 Adapted from Kuru (2005).


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Smaller orders from national suppliers have smaller lead times but issues regarding certification, environmental impact and legality must be considered.

It is important to establish in the tender whether an external third party will be involved in the inspection process. If NRC needs to hire an external inspector, be sure to budget for this cost.

It may make sense for agencies involved in emergency construction to share information and procurement processes. Shared supplier lists should, amongst other details, include:

Figure 8: Table of supplier details required Column heading Explanation Supplier details Name and contact details Country of origin Domestic or international supplier Forest type Plantation or natural forest Type of forest management license

Should be issued by national government

Source of timber If supplier is selling sawn wood rather than logs Certification status Either certified; in process or uncertified Class of certification e.g. FSC or other body Certification checked No. of certificate and if verified Products Logs, sawn timber, plywood etc.

When tendering, suppliers should be requested to provide:

• Copies of timber certification.

• Source of the timber must be clearly stated (ideally a description of the logging process)

• Description of the drying process

• Description of treatments

• Lead time

• Cost according to the specifications

• Description of timber sizes available

• Measures for sustainable management of forest of origin (if not internationally certified)

3.5 Place order

The order should repeat agreed specification as the initial specification sheet, this time including finally agreed prices and delivery times.

If ordering volumes of timber to be delivered in containers, be sure to calculate enough space for the pallets and ensure that pallets are included in the price. If wooden pallets are included they will also require a phytosanitary certificate.

3.6 Delivery

The logistician should ensure that the specifications in the order have been met before the delivery is accepted.

As timber is high-volume, agreements should be made beforehand as to who is responsible for loading / unloading and where timber will be stored before the delivery arrives and whether storage pallets are included in the delivery.

The following is a checklist of actions to take on delivery:

• Check documentation – all certificates etc.


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• Check quantities match

• Check species is correct

• Carry out visual grading checks (see Section ‘ 4.5 Visual grading’)

• Possibility of testing strength through agreed stress test (placing pre-calculated load on a sample piece of timber to see if it breaks)

• Carry out moisture meter check

• Identify any timber not meeting standards, reject and record - getting driver/supplier representative to counter-sign

• Once satisfied with quality of delivery, check storage area is dry and meets requirements

• Check that bales of timber are labeled correctly if receiving large quantities.

When checking large timber deliveries it will only be possible to check a portion of the timber. For example, moisture checks should be carried out on 10% of wood for deliveries of fewer than 100 pieces but it may only be necessary to check 1 or 2% of pieces for deliveries of over 2000 pieces.

Timber will normally be stamped with details of the supplier, stress grade, treatment and the stamp of an independent certifier if appropriate. As stamping standards vary from country to country, it is important to know what information will be included on timber stamp labels.

3.7 Storage

Timber is a high-volume product and considerable storage may be required. A shed or warehouse is sufficient if it is dry and clear of insects to avoid warping, decay and infestation.

Timber should be stored off the ground (hard floor) in a non-stressed position (e.g. laid flat on racks). Layers should be stacked so there is sufficient ventilation and any racks should also be treated to prevent cross-contamination. Small quantities of timber can be stored upright but not resting on a damp floor.

For all storage, a timetable of regular checks should be drawn up to check for signs of rot or insects.

If no building is available, a short-term measure can be to spread fine granular material such as sand or ashes on a well drained space and stack the timbers on bearers off the ground. Timber should be covered with a waterproof sheet to protect it from rain but with enough ventilation to avoid condensation. This is only an emergency, temporary solution.

When importing large volumes of timber, containers not only make shipment and handling easier but can also be used for long-term storage. Annex ‘ 6.7 Container sizes’ gives details of container dimensions.

In an indoor environment, the maximum height of the timber stack should not be more than four times the shortest width of the pack (i.e. a ratio of 4:1). Outside where wind may affect the stack, the ratio should be reduced to 3:1.

If storing bales of timber, the bales must be correctly labeled (see Section ‘ 4.7 Specifying documentation’).

Figure 9: Labelling timber Image © UNIDO (1995b)


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3.7.1 Bamboo storage

Bamboo poles should be stored horizontally off the ground and supported so they do not bend. They should be protected from the sun, rain and moisture.

3.7.2 Health and safety in treatment processes

Normally treatment of wood is outsourced. However, if NRC is treating small quantities of wood itself, consider the following Health and Safety issues, following instructions that come with the chemical itself:

• Verify legality and safety of chemicals purchased

• Reduce contact with treatments by wearing gloves and goggles when handling wood or chemicals

• Do not allow off-cuts to be burnt as fuel

• Waste must be disposed of appropriately

• Hand washing must occur after all contact with chemicals and treated wood, particularly before using the toilet, smoking or eating

• Work clothes must be washed separately (and provided by the NGO)

• Work spaces must be ventilated

• Staff must be trained for lifting heavy loads

• Staff must be trained on usage of chemicals

• Solvent damp timber should be allowed to properly dry off before use

Be aware of the environmental impact of chemicals washed into surface or ground water during treatment processes. Waste water should be appropriately managed in accordance with the treatment instructions.

3.7.3 Fire safety

Usual fire safety procedures in warehousing and storage should be followed. Check that firefighting equipment is available; staff have fire safety training; sufficient firebreaks are present between stacks when storing large volumes of timber etc.

3.7.4 Handling

Health and safety must be considered in handling of timber and poles. Some timber is toxic to humans, and this should obviously not be procured. The main risks associated with timber handling and health risks caused by dust (skin irritation and breathing problems) and injuries caused by poor lifting techniques.

If sawing is to take place on-site, considerations will have to be taken on whether there are associated health risks. These precautions are suggested by the UK Health and Safety Executive in their leaflet on Toxic Woods5:

• Check if timbers used have known ill-health effects.

• Provide an effective dust extraction system which will control exposure to wood dust to below the occupational exposure limits.

• Provide suitable respiratory protective equipment if the above does not adequately control exposure.

• Provide suitable protective clothing to protect susceptible skin areas where timber known to cause skin problems is used. This clothing should be designed so dust does not become trapped between clothing and skin.

• Ensure proper maintenance of any dust extraction equipment and personal protective equipment (PPE).

5 HSE (2003)


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• Ensure employees are adequately trained in the correct use of dust extraction equipment and PPE.

• Ensure good personal hygiene, which will include thorough washing after exposure to dust.

3.8 Distribution and transport

In some cases, prefabrication will be undertaken offsite. In other situations it may be appropriate to distribute large measures of timber materials to be cut on site.

Delivery of timber by truck should always involve making sure that timber lengths are supported with ideally with no overhang.

It is important to load lorries with logs in a proper fashion to avoid accidents. The following is selectively taken from: “Road haulage of round timber – Code of Good Practice”6 and applies to delivery / movement of logs by road:

3.8.1 Truck loading:

Logs should not be loaded transversely on a truck (laid across the width) as this is unsafe. Instead they should be loaded parallel with the length of the truck:

• Each outer log must be restrained by at least two upright supports.

• Logs shorter than the distance between two uprights should be placed in the interior of the load

• Where logs are supported by only two uprights the ends of the outer logs should extend at least 300mm (12 inches) beyond the uprights

• Logs should preferably be laid top to tail alternately so as to ensure an even balance of the load

• For debarked roundwood and for any timber judged to be slippery, at least two load straps per bay are required

• Check the height of the loaded vehicle to make sure that it will pass under any obstruction likely to be met en route

• Inspect and maintain all load securing equipment

3.8.2 Temporary stacking of logs:

• The timber should be stacked at a safe distance from the road, but still easily accessible for the lorry

• The height of the stack should not exceed 2.0 meters from the road surface, unless specifically covered by risk assessment

• The stack face on to the road edge should be flush, the profile line should not have steep slopes

• Ideally, the stacks should be placed on even ground and not between growing trees, stones etc.

• Stacks should be sited so as not to obstruct sightlines around corners in the road

• The stacks should be free from branches, stones and other material

• Stacks on an incline should be positioned to facilitate loading with the lorry facing downhill

• If the ground is not hard and there is a risk of the stack collapsing, bearers should be used under the pile

• Stacks should not restrict the movement of drainage water

6 The Roundwood Haulage Working Party (2002) www.confor.org.uk/timber_transport/pages/case_download.asp

NRC Internal Guideline – Timber Procurement & Specifications // December 2006 // J Fowler & J Ashmore // www.nrc.no section 4 –timber specifications in detail

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4 Timber specifications in detail

The standard of specifications will depend on the situation. The following EXAMPLE specification sheet can be applied to procurement from:

• (A) an international supplier who meets international certification standards;

• (B) a local supplier where there is a functioning government agency and/or representative of an international certification agency;

• (C) a local supplier where no certification is possible.

This table is based on work by George Kuru for FAO in “Development and Implementation of a Wood Procurement Plan for Post–Tsunami Reconstruction in Indonesia”. It is an EXAMPLE ONLY. Exact specifications are CONTEXTUAL.

Figure 10: Example timber specification sheet Timber provided should meet the following specifications. Timber that does not comply will not be accepted on delivery and will not be paid for. 1. Legality SECTION: 5 Chain of custody and certification A, B The timber merchant provide proof of certification by (normally national

government) A, B, C Reduced impact logging procedures used. A, B, C The timber must not come from old growth forest, ancient forest or High

Conservation Value Forests. A, B, C No species on the CITES list (See Section ‘ 5.2.3 CITES’. 2. Accepted Species SECTION: 5 Chain of custody and certification A, B, C To be specified by the engineer (note different species for different timber

products may apply). (Should be stated with botanical name. May be useful to also confirm accepted local name with suppliers to avoid confusion)

3. Certification SECTION: 5 Chain of custody and certification A, B Proof of certification by international, continental or national chain of custody

verifier e.g. FSC. B, C Independent verification by body / individual approved by NRC C No certification available (N.B. A decision on this must be made with

sustainability in mind, and consultation with HQ may be necessary). 4. Treatment SECTION: 4.1 Specifying treatments A, B, C Pressure treated CCB with anti-termite topical application A, B Meets requirements for Hazard Class 3 (external timber not in contact with

ground) C Timber is free of pests and fungal infections any treatments (e.g. creosote)

must be made along the entire length of the timbers to a depth of 5mm. 8. Moisture content SECTION: 4.2 Specifying moisture content A, B, C Seasoned / Dried to 15% MC C Specify drying method and time 5. Grading system SECTION: 4.3 Specifying strength grades A, B Internationally recognized grading system (specify which in relation wit which

standard e.g. ISO) B National grading system (specify how grades are defined and in relation to

which standard) C Informal local grading system (specify how the grades are defined) 6. Grade SECTION: 4.3 Specifying strength grades A, B, C Class I, II, III etc as defined by the grading system. 7. Durability SECTION: 4.4 Specifying durability A,B,C Timber must have a natural durability of X years and a seasoned/treated

durability of Y years.


15

9. Visual Grading SECTION: 4.5 Visual grading 9.a. Sawn timber SECTION: 4.5 Visual grading A, B, C Sloping grain 1 1 in 8 (see section 4.5.1 Sloping grain) Sound Knots 2 1/3 dimension of face, to max of 10cm dia. 1 per meter

in length Unsound knots or Knot holes

3 1/4 dimension of face, to max of 7cm dia. 1 per 3 meter in length

Decay (Rot) 4 None, except in an unsound Knot Sound Sapwood, including Wane

5 1/3 sum of width and thickness

Compression failures 6 None Stain free from decay 7 Unlimited End Splits 9 Longest split, 15cm at each end Open shakes, Surface checks and End checks

10 1/2 thickness

Sawn 11 May specify backsawn, quartersawn etc. WARPING 12 BOW: 1 cm in 3m; CUP: 1 cm in 3m; SPRING: 1 cm in

3m; TWIST: 1 cm in 3m 9.b. Timber poles SECTION: 4.5 Visual grading Sweep / Crook

Pole does not deviate from middle axis

Taper Not exceed 5-10mm per meter Spiral grain No ‘twisted’ trees End splitting

Splits should not extend more than 100mm along the length of the pole from end to end

Splits from handling

Serious splits or damage to outer fibers caused by storing, transporting etc. will result in rejection of pole.

10. Quantities required SECTION: 4.6 Deviation Dimensions of quantities required should not deviate more than 5% of the

required sizes (for sawn timber). Conditions can also be placed on timber pole dimensions.

4.1 Specifying treatments

The best way to protect timber is through design to keep it as dry as possible (though termites can still attack dry timber). Construction design itself – for example keeping timber out of contact with the ground – can greatly reduce the risk of termite infestation or rotting. Preservatives based on borax, soda, potash, wood tar, beeswax and linseed oil are generally considered to be non-poisonous though health and safety conditions must still be carefully followed.

Timber can be pressure-treated or non-pressure treated. When making small, local purchases non-pressure processes are more likely to be used.

Non-pressure processes include the application of the preservative by means of brushing or spraying, dipping, soaking, steeping or by means of hot and cold bath.

Pressure processes are carried out in closed cylinders with applied pressure and/or vacuum. In most cases, a deeper and more uniform penetration and a higher absorption of preservative is achieved than in non-pressure treatments. Another advantage is that the treating conditions can be controlled so that retention and penetration can be varied.

Checking which treatment is important since many chemicals banned in industrialized countries are still used in developing countries, sometimes recommended by government. Processes containing DDT (dichlor-diphenyl-trichlorethane), PCP (pentachlorphenol), Lindane (gamma-hexa-chloro-cyclohexane) and arsenic should be


16

rejected. CCA (Copper, Chrome and Arsenic) is a common preservative used which may be very toxic. Annex 6.10 Timber treatments requiring expert handling (New Zealand) lists those timber treatments that require some expertise in handling.

A website that may help you identify the level of hazard of a treatment is the UK Control of Substances Hazardous to Health (COSHH) website 4http://www.coshh-essentials.org.uk/.

The Globally Harmonized System (GHS) 7 for the classification and labeling of hazardous chemicals is an initiative to promote common, consistent criteria for classifying chemicals. It is due to be ready by 2008.

4.1.1 Preservatives / treatments

The preservative used will depend on what context the timber is to be used in – e.g. externally or internally. In order to understand this it is important to read Section ‘ 4.1.2 Hazard classes’ below.

There are 3 main preservatives to protect timber against rot and pests:

• Oil-based: The most common is creosote (obtained by the distillation of coal tar), often diluted with cheap petrol oil.

• Water-borne: These are very common but can swell, twist, split and check timber more than other treatments.

‘Non-fixed’ include boron compounds and are environmentally friendly but can not protect against very wet conditions as the treatment can be washed out.

‘Fixed’ preservatives (also called ‘leach resistant’) are for external use and may have problems with health and safety in terms of toxicity.

• Light Organic Solvent Preservatives (LOSP): Organic substances are dissolved in oil or spirit and banned in many countries.

Oil-based treatments include pentachlorophenol, copper naphthenate, and creosote and may be applied as a ‘paint’ or under pressure. All of them are toxic to humans. Creosote can be used for timber used externally (hazard classes 3, 4, and 5 following the British Standard). Linseed oil has been used as an ‘envelope’ treatment (not penetrating timber more than 5mm) and is cheaper than other treatments (though not as effective) as it uses a lower quantity of treatment.

Water-borne treatments can be low-pressure or high-pressure. They are made up of small amounts of fungicide/insecticide dissolved in water, to which a dye is sometimes added. Low-pressure treatments are quick-drying and in general construction meeting hazard classes 1, 2 and 3 (BS). High pressure treatments maximize the penetration of timber and are suitable for all hazard classes.

Water-borne treatments include: copper compounds such as Chromated copper arsenate (CCA) (highly toxic) and Alkaline copper quaternary; borate preservatives (non toxic to humans but can be washed out of timber); Bifenthrin spray preservatives which only penetrate timber 2mm (not clear how well they protect against insects.)

Light Organic Solvent Preservatives are similar to low-pressure water-borne treatments but replace water with white spirit as a solvent. They are normally used for hazard classes 1, 2 and 3 (BS). As they do not affect the surface of timber, they are often used to protect timber used in joinery. LOSP treatment is normally expensive. Attempts to use water as a solvent have resulted in similar welling effects

7 http://www.unece.org/trans/danger/publi/ghs/ghs_welcome_e.html


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as Water-bourne treatments. LOSP treated wood should not be used where it may come into contact with public drinking water.

4.1.2 Hazard classes

Hazard class is the classification of timber according to the risk it is exposed to and therefore what preservative will be required. At present there is no comprehensive internationally agreed hazard class system for either timber classification or the chemicals that can be used. Different countries or regions have their own classification systems, but they are broadly similar apart from an extra classification in countries prone to termites.

The first table below uses the New Zealand and South African Hazard Classes (HC) while the second used the British:

HC (NZ/SA) Description 1 Timber not exposed to weather – frames / internal e.g. doors, roof

trusses, floor boards 2 As above and protected from termites 3 Timber exposed to the weather but not in contact with the ground

e.g. cladding, log-homes 4 In contact with the ground – fence posts etc. 5 Timber exposed to ‘continual wetting’ 6 Marine use – jetties etc. HC (BS/EN 335)

Description

1 Internal, with no risk of wetting 2 Internal, with risk of wetting 3 External, above damp proof course 4 In permanent contact with the ground or fresh water 5 In permanent contact with sea water

See the South African Wood Preservers Association website for a simple summary of hazard classes: http://www.sawpa.org.za/HazardClassifications.htm.

4.1.3 Penetration classes

Penetration specification is used for determining how far preservative treatments will enter wood. As with durability and hazard classes, definition will vary from country to country. An example is given below of the British Standard for penetration classes. When agreeing on treatment of timber it is important to be aware of what level of penetration into the timber is required.

Figure 11: Penetration classification based on BS 351-1

Penetration class Penetration requirement

P1 None P2 Minimum 3 mm lateral and 40 mm axial into sapwood P3 Minimum 4 mm lateral into sapwood P4 Minimum 6 mm lateral into sapwood P5 Minimum 6 mm lateral and 50 mm axial into sapwood P6 Minimum 12 mm lateral into sapwood P7 Minimum 20 mm into sapwood P8 Full sapwood P9 Full sapwood and minimum 6 mm into exposed heartwood

4.1.4 Bamboo treatment

http://www.sawpa.org.za/HazardClassifications.htm


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This information comes from: http://bambus.rwth-aachen.de/eng/PDF-Files/Bamboo%20as%20a%20building%20material.pdf

• Smoking: Bamboo can be smoked in its own resin which makes it unpalatable to insects.

• Heating: Bamboo is heated in kilns to ca. 150°C for a short time

• Immersion: Freshly cut canes are immersed in water for 4-12 weeks. The nourishment for insects (starch and sugar) is removed. Streams are more suitable than stagnant ponds. Saltwater is not suitable, because the salt will stay in the bamboo and can bring moisture and fungi into the canes.

• Impregnating coatings: Coatings with borax are ecological and widely used. In addition, lime slurries, rangoo oil or slurries from lime or cow dung are also used.

The life time of non-treated bamboo will be ca. 2 1/2 years whereas treated bamboo will be ca. 10 years.

The Environmental Bamboo Foundation has produced a very detailed and easy to understand guide to bamboo preservation using a Vertical Soak Diffusion method and a preservative known as TimBor. The guideline can be downloaded here: http://www.bamboocentral.org/index1.htm.

4.1.5 Timber pole treatment

Timber poles can be treated with pressure or non-pressure treatments. In situations where pressure treatments are not available, non-pressure treatments such as those listed above for timber are likely to be used. It should be noted that brushing/spraying may lead to a lot of preservative treatment leaking into the surrounding environment while both brushing/spraying and simple immersion techniques offer only limited protection. See Jayanetti and Follett (2000) for detailed information on treating timber poles in situations of limited technology.

4.1.6 Local treatment

In non-industrialized countries, creosote or a mix (2:1) of waste engine oil and diesel can be used to treat externally-exposed wood and bamboo or for internal beams in buildings that will not be used for habitation.

4.2 Specifying moisture content

Moisture content should normally be specified as being below 14%. This is verifiable with an electronic moisture meter (see Annex ‘ 6.9 Measuring moisture content’) and timber from a large supplier should comply.

Specifying moisture content for timber poles may be more difficult, though drying methods can be specified and samples of the poles tested (again see Annex ‘ 6.9 Measuring moisture content’). Poles normally need to be dried to at least 25% before preservative treatments can be used and this can take months, even in dry conditions. Some preservatives can be applied when the poles are green.

4.3 Specifying strength grades

Timber strength depends on the species of tree, though timber qualities can vary even when timber is sourced from the same species. It is common to grade timber in different stress or strength classes so that an engineer can specify the class of strength required rather than the species of tree so that the timber required meets the strength specifications for construction rather than simply comes from a specific species.

Strength grading classification differs between countries and may be termed ‘strength’ or ‘stress’ grades. In this document we will use ‘strength grade’ to cover both strength

http://bambus.rwth-aachen.de/eng/PDF-Files/Bamboo as a building material.pdf

http://bambus.rwth-aachen.de/eng/PDF-Files/Bamboo as a building material.pdf

http://www.bamboocentral.org/index1.htm


19

and stress grades. Official strength classification is normally made on a combination of machine-tested measurements and visual grading. Annex ‘ 6.5 Comparison of strength grades’ offers a very rough guide for comparison of different standards. Strength grading is not necessarily related to appearance grading.

Machine strength grading exploits the relationship of stiffness to strength by measuring the resistance of each piece of timber to flexing.

Visual strength grading assesses the size, frequency and positions of characteristics such as knots, wane, sloping grain and other factors which affect strength. Grading rules lay down the allowable limits for each grade.

In the absence of an established national grading system, procurement from a local supplier can establish a strength specification by agreeing on:

• Species

• Visual grading specifications

• Density (common density for softwoods used in construction is between 450 and 550 kg/ m).

4.4 Specifying durability

Durability varies by species. Heartwood is naturally more durable than sapwood. There is no internationally agreed specification for durability. However, the Australian classification8 gives a good guide to what might be demanded. Their classification is based on trials of resistance to pests and decay of untreated heartwood in the ground.

Figure 12: Australian durability classes Class Description No. of years durability in the

ground No. of years durability above the ground

1 Highest durability 25 years + 40 years + 2 High durability 15-25 years 15-40 years 3 Moderate durability 5-15 years 7-15 years 4 Low durability 0-5 years 0-7 years

4.5 Visual grading

Visual grading is useful in situations where the supplier is unable to grade their timber mechanically as well as an important technique for checking timber quality.

Visual grading is a complex and difficult procedure and professionals undergo considerable training to become qualified. However, in circumstances where small quantities of timber are being purchased and NRC logisticians are involved in evaluating deliveries, some of the following basic guidelines may be of use.

When visually grading timber, all surfaces should be checked and the timber is normally rolled along its length to reveal any obvious warping. Timber that is though not to meet the required specifications should be placed in a separate pile for double-checking and it would be advisable to have a representative of the supplier (perhaps the delivery driver) to acknowledge and sign for defective timber.

Visual grading involves the following components9:

8 http://oak.arch.utas.edu.au/glossary/view_glossarylist.asp?term=D 9 Images in this section are from UNIDO (1995a)


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4.5.1 Sloping grain

The slope of the grain on timber (i.e. the direction of the grain in relation to the length of the timber) can greatly affect the strength of timber.

Allowable slope of the grain is specified as a gradient, for example ‘1 in 8’, which means for every 8 centimeters along the edge of the timber the grain rises or falls by 1 centimeter.

4.5.2 Knots

A knot is the remains of a branch which has been embedded in the tree trunk as the tree has grown. Knots weaken the strength of timber as they change the direction of the grain. Limits on knot sizes are therefore made in relation to the width of the face and location on the face in which the knot appears (knots near the edge of a board cause greater problems than knots in the middle).

A sound knot is one which is as strong as the surrounding wood and shows no sign of decay. An unsound knot is a weakness in the wood and is softer, chipped or shows other signs of decay.

Specification for knots is expressed as the size of the knot in relation to the width of the timber and the number of knots per length or meter of timber.

4.5.3 Decay

As explained in section ‘ 4.1 Specifying treatments’, decay is caused by fungus, bacteria or pests. Early stages of decay can be very difficult to identify so any timber showing any signs of decay or insect infestation should be rejected.

Pests will often leave boring holes in the wood. It is important to have someone experienced in identifying decay involved in the visual grading verification.

4.5.4 Sapwood

Sapwood in timber will be less strong than the heartwood and in softwoods is treated to improve its durability. A limit may be placed on the amount of sapwood to be present in a timber board, this will be determined by what the timber will be used for. If a hardwood is being ordered (unlikely) then any sapwood present will be considered ‘wane’.

4.5.5 Wane and want

Wane is the absence of wood from the face or edge of timber due to the board being cut near the edge of a log. This is normally expressed as a percentage or fraction of the width and/or thickness of timber. Want is the absence of wood due to some of the timber being split off in processing. See ‘Figure 15: Measuring the wane’.

Figure 13: Measuring the slope of the grain Image © UNIDO (1995a)

Figure 14: Measuring a knot Image © UNIDO (1995a)


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4.5.6 Compression failures

These result in fracture of wood fibers across the grain due to excessive compression. Timber is normally required to be free of all such fractures.

4.5.7 Split

A split is a separation of fiber bonds ACROSS the annual rings. A split is a separation that continues all the way through to an adjacent or opposite side of the timber. A split is measured by its length along the board and a maximum length of split, e.g. 15cm, is stated in specifications. See ‘Figure 16: Measuring split’.

4.5.8 Checks

A check is a separation of fiber bonds ACROSS the annual rings. A check is a shallow crack and does not carry all the way through an edge or face of a timber board. The limit on acceptable checks is normally expressed through a limit on their absolute length. See ‘Figure 17: Measuring checks’.

4.5.9 Shakes

Shake is a separation or a weakness of fiber bond BETWEEN the annual rings, that is presumed to extend lengthwise without limit. Shake affects shear strength more than compression strength so specifications for the amount of allowable shake may vary depending on the timber’s purpose. Shake allowance may be restricted to avoid decay caused by moisture entering into the fiber separations. ‘Figure 18: Shake’ illustrates how shake is a gap between the rings.

Figure 15: Measuring the wane Image © UNIDO (1995a)

Figure 16: Measuring split Image © UNIDO (1995a)

Figure 17: Measuring checks Image © UNIDO (1995a)

Figure 18: Shake Shake is a gap between the rings, shown by the dark line.


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4.5.10 Warping

‘Warping’ is any variation from a true, flat surface. The following terms are used and the amount of acceptable warp is expressed by the amount of deviation per length of timber:

Figure 19: Different types of warp Bow: Curve along the length of a board. Specify how much deviation (b) is allowed along length (a) e.g. (b) is maximum 1cm per 3metres of length.

Cup: Curve across the grain or width of a board. Specify how much deviation (b) is allowed along width (a) e.g. (b) is maximum 1mm per 100mm of width.

Spring: Curve along the edge of a piece but not affecting the face. Specify how much deviation (b) is allowed along length (a) e.g. (b) is maximum 1cm per 3metres of length.

Twist: Spiral distortion along the length of timber. Specify how much deviation (b) is allowed along length (a) e.g. (b) is maximum 1cm per 3metres of length.

4.5.11 Timber poles grading

Timber poles have the following features for grading:

Taper – this is the natural thinning of a pole towards its tip. The change in diameter should not be more than 5-10mm per meter of pole length.

Straightness – poles can have ‘sweep’, where a pole bends like a banana, or ‘crook’ where a pole is crooked. Poles are usable if they sweep or crook deviation never falls be the central axis of the pole (draw an imaginary line from end to end of the pole and there should always be a part of the pole in the axis).

Spiral grain – poles from trees that have grown in a twisted manner should be rejected.

Splitting – no splits large than 100mm should be present at the ends of the poles.

Degrade – poles showing insect or fungal attack should be rejected

Damage from felling – poles that show severe damage from the logging process should be rejected.

4.6 Specifying quantities and finishing

4.6.1 Quantities

Specific lengths will be determined by the particular project. Decisions should be made as to whether the timber is to be cut to size by the supplier or whether it will be

Z


23

cut on site. An important factor that may influence this decision is the availability of transport that can carry long lengths of timber.

An example of quantity specification is reproduced here. Note the different uses of timber may require using different species in the same order:

Roofing Product Dimension Qty Volume (m3) Roofing beams 5cmx10cmx4m 16 0.320 External walls Product Dimension Qty Volume (m3) External wall planks

2cmx20cmx6m 65 1.560

Timber poles Product Dimension Qty Volume (m3) Small poles 50mm radius X

3metres 50 (Volume = pi * r2 x height) = 0.024m3

*50 = 1.2m3 Large poles 100mm radius x

3metres 10 (Volume = pi * r2 x height) = 0.094m3

*10 = 0.94m3 It is important to be aware of shrinkage of timber and quoted sizes may be smaller on arrival. This should be checked with the supplier beforehand.

A useful resource online is “The Shrinkulator” which assists calculations for shrinkage: http://www.woodbin.com/calcs/shrinkulator.htm.

4.6.2 Finishing

Finishing may be required on any wood that will be used internally rather than for external construction (where sawn timber remains ‘rough’). Timber normally loses 1-2mm in finishing. Poles lose considerable amounts of volume during sawing (40%).

4.7 Specifying documentation

When an international delivery of timber arrives at port, it will normally require the following documentation, though specific requirements will change from country to country:

• Invoice

• Packing list of contents

• Phytosanitary certificate from the port of loading (this will have details of treatments added to the timber and will normally list the chemicals used, their concentration etc.)

In addition, NRC should also demand:

• Certificate of legality

• Certificate of sustainability from third-party (see Section ‘ 5 Chain of custody and certification’)

With large deliveries, the following information should be printed on the timber bales to facilitate identification at a later date:

• Bale number

• Dimensions of the pieces and no. of pieces in bale

• Manufacturer’s company name and address

• Preservative used

• Date of labeling

• Date of verification of inspection

http://www.woodbin.com/calcs/shrinkulator.htm

NRC Internal Guideline – Timber Procurement & Specifications // December 2006 // J Fowler & J Ashmore // www.nrc.no section 5 – chain of custody and certification

24

5 Chain of custody and certification

5.1 Definition of chain of custody

It is hard to know what kind of forest a piece of timber has been cut came from. Tracing back the history of a piece of timber can be extremely difficult in countries where national law is weak and timber is highly profitable (and sometimes illegal). Certificates can be faked and corruption in the timber industry may make relying on national government certification impossible while in some countries timber can be an extremely dangerous and violent industry to be involved in.

The chain of custody is the process where the source of timber can be verified. All the processes that timber goes through – felling, transporting, sawing, storage etc. – are checked to ensure that there is no risk that timber coming from certified forests could be replaced or mixed with non-certified timber unless this is also recognized in the label.

The chain of custody of sawn timber is much harder to follow than the chain of custody for logs / poles. This may be an important consideration in tendering though if logs are to be purchased for sawing rather than timber poles being purchased for direct building, the capacity for treatment and sawing that follows recommended national and/or international guidelines should be established beforehand.

It is important to use a respected and trusted inspection company to verify the chain of custody as, unless perhaps procurement is local and in small quantities, this is an activity that can not be carried out by NRC.

In the absence of any possibility of international certification or national law (e.g. timber purchased locally in small quantities) NRC will have to develop its own basic standards that a local supplier can follow (i.e. they must have a replanting program in operation etc.). It should be emphasized that this situation is far from idea.

5.2 Certification – legal or sustainable

Certification may certify whether a timber product is legal and/or sustainable. Legal timber is not necessarily from a sustainable forest, it is simply not from an illegal logging forest. Sustainable certification verifies whether the forest a wood product comes from has a re-planting program and is environmentally sound.

Certification guarantees that wood products travel through a verified chain of custody with regular inspections carried out along the chain.

There are several international or regional certification bodies. Normally forestry or wood-product companies pay for the inspection costs and the certification agencies are, to some extent, competing to offer companies the ‘best value’ certification. Some of the main certification organizations are:

FSC - Forest Stewardship Council www.fsc.org FSC certification is carried out by FSC accredited certification bodies. FSC itself does not certify forest operations or manufacturers. FSC provides monthly updates on the certificates issued by FSC accredited certification bodies. The latest lists are available in the Certificates Lists on its website. PEFC: Pan European Forest Certification Scheme www.pefc.org

Figure 20: Chain of Custody

Forestry company [‘round timber’]

Saw mill [‘sawn wood’]

Sawn wood merchant [‘humid’ sawn wood]

Merchant [transports & sells timber]

Drying service [dry ‘sawn wood’]

http://www.fsc.org/

http://www.pefc.org/


25

PEFC is a global umbrella organization for the assessment of and mutual recognition of national forest certification schemes. PEFC has in its membership 32 independent national forest certification systems of which 22 to date have been through a rigorous assessment. These 22 schemes account for over 191 million hectares of certified forests making PEFC the world's largest certification scheme.

The Sustainable Forest Initiative www.aboutsfi.org Focusing particularly on paper, SFI certifies different types of forest products.

Certisource www.certisource.net Certisource certificates legal, rather than sustainable wood products and sees itself as a process to be used alongside FSC.

5.2.1 Other certifiers

There are a number of regional or national certifiers and national governments may issue licenses to forestry companies and saw mills. This should be verified with the relevant government department.

It may be possible to use a private inspection company. In this case, the following should be considered:

• Which stage of the chain of custody an inspection company will be inspecting (it may be necessary to use more than one inspection company

• Whether the company can prove their trustworthiness and independence

• The Terms of Reference for the inspection company – i.e. are they being hired to establish whether quality is being met; processing standards are being followed; environmental concerns are being respected or timber is legal?

5.2.2 Reduced impact logging (RIL)

Reduced impact logging (RIL) is a method for sustainably managing a forest. In this instance trees are carefully selected for logging rather than whole areas of forest felled at any one time. Access roads are reduced in width with RIL and logs can be sawn where they fall with mobile saw mills to reduce the impact of extracting the log from the forest. The following is taken from:

5http://www.itto.or.jp/live/PageDisplayHandler?pageId=129

“Reduced impact logging can be defined as 'the intensively planned and carefully controlled implementation of timber harvesting operations to minimize the environmental impact on forest stands and soils'. It involves a number of practical measures, such as:

• a pre-harvest inventory and the mapping of individual crop trees;

• the pre-harvesting planning of roads, skid trails and landings to minimize soil disturbance and to protect streams and waterways with appropriate crossings;

• pre-harvest vine-cutting in areas where heavy vines connect tree crowns;

• the construction of roads, landings and skid trails following environmentally friendly design guidelines;

• the use of appropriate felling and bucking techniques including directional felling, cutting stumps low to the ground to avoid waste, and the optimal crosscutting of tree stems into logs in a way that maximizes the recovery of useful wood;

• the winching of logs to planned skid trails and ensuring that

http://www.aboutsfi.org/

http://www.certisource.net/


26

• skidding machines remain on the trails at all times;

• where feasible, using yarding systems that protect soils and residual vegetation by suspending logs above the ground or by otherwise minimizing soil disturbance; and

• conducting a post-harvest assessment in order to provide feedback to the resource manager and logging crews and to evaluate the degree to which the RIL guidelines were successfully applied.

Apart from the environmental benefits, RIL has been shown to reduce the percentage of 'lost' logs (those trees that are felled in the forest but not extracted because they aren't seen by tractor operators), thereby reducing timber wastage.

5.2.3 CITES

CITES (The Convention on International Trade in Endangered Species of Wild Fauna and Flora) is an international treaty that aims to protect certain plants and animals threatened by international trade. The Convention provides for three levels of protection:

• Appendix I – threatened with extinction

• Appendix II- not immediately threatened with extinction, but require management

• Appendix III – listings that are country specific

Designated CITES authorities in each member country are the only authorized issuers of certificates. Any trade in CITES specimens without CITES documents is regarded as illegal. See www.cites.org for more information and Annex ‘ 6.2 CITES Appendices for timber’ for a list of tree species covered in CITES’ Appendices.

5.2.4 ISO: International Organisation for Standardisation

There are numerous international standards for timber as defined by the ISO (www.iso.org). ISO standards that complement chain of custody certification are from the 14000 series which provide a standard for environmental management in processing. Contacts for the country office for members of ISO can be found here: www.iso.org/iso/en/aboutiso/isomembers/MemberCountryList.MemberCountryList

Standards exist for all aspects of timber, standards for timber structures are grouped under TC 165.

5.2.5 National standards

National standards vary between countries, though in Europe there are attempts to standardize different national standards. Normally it is necessary to purchase copies of national standards from the issuing authority and most national standards can be bought at: http://www.saiglobal.com/shop/Script/search.asp. Here are links for some of the standards most likely to be encountered:

• British and European standards: http://www.trada.co.uk/techinfo/asset/send/886/content/wis4-19/index.html#d0e286

• Eurocode 5 will supersede some British Standards and more information can be found here: http://www.bsi-global.com/Eurocodes/Progress/eurocode5.xalter

• Canadian (click on Forest Products): http://construction.csa.ca/

• American Wood Council: http://www.awc.org

• New Zealand: http://www.standards.co.nz

• Australia: http://www.standards.org.au/

http://www.iso.org/

http://www.iso.org/iso/en/aboutiso/isomembers/MemberCountryList.MemberCountryList

http://www.saiglobal.com/shop/Script/search.asp

http://www.trada.co.uk/techinfo/asset/send/886/content/wis4-19/index.html#d0e286

http://www.trada.co.uk/techinfo/asset/send/886/content/wis4-19/index.html#d0e286

http://www.bsi-global.com/Eurocodes/Progress/eurocode5.xalter

http://construction.csa.ca/

http://www.awc.org/

http://www.standards.co.nz/

http://www.standards.org.au/

NRC Internal Guideline – Timber Procurement & Specifications // December 2006 // J Fowler & J Ashmore // www.nrc.no section 6 – annexes

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6 Annexes

6.1 Glossary of terms

Term Meaning Board A term used for a piece of timber which is wider than it is thick.

Cellulose Complex sugar-based chemicals in a tree providing strength and elasticity to timber.

Chain of custody Process through which wood passes from tree to finished wood product and can be traced back to its origin through inspection.

Check Separation of fibers along the grain and across the growth rings. The crack formed does not run from face to face.

Compression failure Fracture of wood fibers across the grain resulting from compression along the grain.

Crook Deviation of a timber pole from a straight axis involving more than one bend.

Degradation Anything that lowers the value of wood e.g. rot/decay (from fungus or bacteria), damage by insects or damage in felling/transport.

Durability class Classification determined by how many years timber will last above ground with and without treatment (seasoned or natural durability) at a constant moisture content.

Figure The markings on the surface of sawn timber formed by the structural features of the wood.

Grain Direction of the wood fibers relative to the main length axis of the timber.

Grain, sloping Deviation of grain from being parallel to the longitudinal axis of a board.

Hazard class The classification of timber by what ‘hazard’ it will be exposed to – e.g. whether it is to be used internally or externally or if it will be in contact with the ground or not.

Heartwood The centre of a tree, darker in color, providing the structural strength.

Knot Remains of a branch embedded in the tree trunk which appears as a dark round circular shape on timber board.

Knot, sound A solid knot that is as hard as the surrounding wood, and shows no sign of decay.

Lignin Bonding agent in the cellular structure of timber.

Moisture Content Weight of moisture in timber expressed as a percentage of its oven-dry weight (MC).

Name, Latin / common

Tree species have two names. The common name varies around the world while the Latin, or botanical, name is universally accepted.

Penetration class The classification of treatments by how far it will penetrate timber. Note the penetration properties of timber vary between species.

Pole, peeled / rounded

Timber poles are un-swan logs. Rounded or peeled poles are poles with the bark removed, stripped to a regular size. Also known as ROUND TIMBER.

Primary wood Timber from slow-growing forests, usually hardwood. Used mostly in joinery/furniture.

Rings, growth/annual The rings marking the growth of the tree seen in a transverse tree section.

Sapwood Surrounding the heartwood, contains the living cells and is lighter in color and more penetrative and vulnerable to insect attack and rot than heartwood.

Sawn, back / quarter A division of timber by the angle of the rings to the wide face age. Quartersawn is where the rings are at an angle of not less than 45 degrees to the face.

Seasoning (also air/kiln drying)

Drying of wood, by stacking and allowing it to dry in the air (unforced) or drying in an oven (forced), to reduce moisture content and improve durability.

Secondary wood Timber from fast-growing forests, usually softwoods, that will require seasoning and treatment. Used mostly in construction.

Shake Fracture of the wood fibers between the growth rings caused by stresses caused by factors other than shrinkage.

Shrinkage Linear shrinkage is caused by reduction of moisture content below fiber saturation point and expressed as a percentage of the original dimensions or volume of timber.

Strength/ stress grade Classification of timber’s ability to bear stress without breaking/weakening.

Sweep Deviation of a timber pole from a straight axis involving one bend, like a banana.

Taper When a pole this towards one end.

Wane The absence of wood on any face or edge of a piece of timber.

Warp Variation of a surface from a straight axis. It includes bow, spring, cup and twist and may be due to irregular seasoning.


28

6.2 CITES Appendices for timber

The following information summary is from US Fish and Wildlife Service http://www.fws.gov/citestimber/timber/treespecies.html

Some CITES-listed tree species are traded as medicinal or horticultural specimens and rather than timber.

6.2.1 CITES Appendix 1

Species Common Name

Abies guatemalensis Guatemalan fir

Araucaria araucana Monkey-puzzle tree

Balmea stormiae Ayuque

Chrysalidocarpus decipiens Butterfly palm

Dalbergia nigra Brazilian rosewood

Fitzroya cupressoides Alerce, Chilean false larch

Pilgerodendron uviferum Pilgerodendron

Podocarpus parlatorei Parlatore’s podocarp, Monteromero


Species Common Name CITES ref.

Aquilaria malaccensis Agarwood, Aloewood #1

Aquilaria spp. Agarwood #1

Beccariophoenix madagascariensis Manarano palm

Caryocar costaricense Ajo #1

Gonystylus spp. Ramin #1

Guaiacum officinale Commoner lignum vitae #2

Guaiacum sanctum Holywood lignum vitae #2

Guaiacum spp. (all species except those with earlier date in Appendix II)

Lignum vitae #2

Gyrinops spp. Agarwood #1

Lemurophoenix halleuxii Red-lemur palm

Marojejya darianii Ravimbe palm

Neodypsis decaryi Triangle palm #1

Oreomunnea pterocarpa Gavilan #1

Pericopsis elata Afrormosia, African teak #5

Platymiscium pleiostachyum Cristobal, Granadillo, Cachimbo

#1

Podophyllum hexandrum Himalayan may-apple #2

Prunus africana African cherry, Stinkwood #1

Pterocarpus santalinus Red sandalwood, Redsanders #7

Ravenea louvelii Lakamarefo palm

Ravenea rivularis Gora palm

Satranala decussilvae Satranabe palm

Swietenia humilis Pacific coast mahogany #1

http://www.fws.gov/citestimber/timber/treespecies.html


29

Swietenia macrophylla Bigleaf mahogany #6

Swietenia mahogoni Caribbean mahogany #5

Taxus chinensis Chinese yew #10

Taxus cuspidata Japanese yew #10

Taxus fauna Chinese yew #10

Taxus sumatrana Chinese yew #10

Taxus wallichiana Himalayan yew #10

Voaniola gerardii Voanioala palm


Species Common Name Listing Country CITES ref.

Cedrela odorata Spanish cedar Populations of Colombia & Peru

#5

Dipteryx panamensis Almendro Costa Rica

Magnolia iliifera var. obovata Giogi, Champak Nepal #1

Podocarpus neriifolius Black pine podocarp Nepal #1

Tetracentron sinense Tetracentron Nepal #1

CITES Annotations (references):

• #1 Designates all parts and derivatives, except: (a) seeds, spores and pollen (including pollinia); (b) seedling or tissue cultures obtained in vitro, in solid or liquid media, transported in sterile containers; and (c) cut flowers of artificially propagated plants.

• #2 Designates all parts and derivatives, except: (a) seeds and pollen; (b) seedling or tissue cultures obtained in vitro, in solid or liquid media, transported in sterile containers; (c) cut flowers of artificially propagated plants; and (d) chemical derivatives and finished pharmaceutical products.

• #5 Designates logs, sawn wood, and veneer sheets.

• #6 Designates logs, sawn wood, veneer sheets, and plywood.

• #7 Designates logs, wood-chips, and unprocessed broken material.

• #10 Designates all parts and derivatives except: (a) seeds and pollen; and (b) finished pharmaceuticals products.


30

6.3 Timber sizes comparison

Taken from http://en.wikipedia.org/wiki/Timber

Examples of variations in ‘standard’ sizes between countries.

Softwood Dimensional Lumber Sizes (US standard) Nominal Actual Nominal Actual 1 × 2 ¾″ × 1½″ (19×38 mm) 2 × 2 1½″ × 1½″ (38×38 mm) 1 × 3 ¾″ × 2½″ (19×64 mm) 2 × 3 1½″ × 2½″ (38×64 mm) 1 × 4 ¾″ × 3½″ (19×89 mm) 2 × 4 1½″ × 3½″ (38×89 mm) 1 × 6 ¾″ × 5½″ (19×140 mm) 2 × 6 1½″ × 5½″ (38×140 mm) 1 × 8 ¾″ × 7¼″ (19×184 mm) 2 × 8 1½″ × 7¼″ (38×184 mm) 1 × 10 ¾″ × 9¼″ (19×235 mm) 2 × 10 1½″ × 9¼″ (38×235 mm) 1 × 12 ¾″ × 11¼″ (19×286 mm) 2 × 12 1½″ × 11¼″ (38×286 mm) 3 × 4 2½″ × 3½″ (64×89 mm) 2 × 14 1½″ × 13¼″ (38×337 mm) 4 × 4 3½″ × 3½″ (89×89 mm) 6 × 6 5½″ × 5½″ (140×140 mm) 4 × 6 3½″ × 5½″ (89×140 mm) 8 × 8 7¼″ × 7¼″ (184×184 mm)

Examples of Dimensional Lumber Sizes (Softwood and Hardwood)

Inch name Metric equivalent Swedish Australian

2 × 4 50 x 100 mm 45 × 95 mm 45 x 90 mm

1 × 3 25 × 75 mm 22 × 70 mm 19 x 70 mm

3 × 3 75 × 75 mm 70 × 70 mm 70 x 70 mm

2 × 7 50 × 175 mm 45 × 170 mm Not used

2 × 3 50 × 75 mm 45 × 70 mm 45 x 70 mm

1 × 4 25 × 100 mm 22 × 95 mm 19 x 90 mm

1 × 5 25 × 125 mm 22 × 120 mm 19 x 120 mm

2 × 5 50 × 125 mm 45 × 120 mm 45 x 120 mm

http://en.wikipedia.org/wiki/Timber


31

6.4 Phytosanitary certificate examples

6.4.1 Chinese phytosanitary certificate.

From http://www.tcmtreatment.com/phytosanitary.htm

http://www.tcmtreatment.com/phytosanitary.htm


32

6.4.2 Example of phytosanitary requirements for suppliers - UK

Edited from: Guidance Notes from UK Forestry Commission Completion of the Phytosanitary Certificate Application Form PH25:

(www.forestry.gov.uk/pdf/guidancephytoapps.pdf/$FILE/guidancephytoapps.pdf)

Part 1 – ‘Name of Applicant’

Part 2 – ‘Address of Applicant’

Part 3 – ‘Address where goods will be available for inspection (if different from Part 2)

Part 4 – ‘Services Required/Details of Consignment(s) ’ - enter

a. The name of the consignee receiving the goods in the importing country

b. The address of the consignee

c. The name of the seaport or airport in the importing country

d. The name of the seaport or airport in Great Britain

e. The date of export from GB

f. This section concerns the description of the wood or wood products which are subject to phytosanitary control. Reference to the numbers of wooden pallets, crates, boxes, packing cases, cable drums etc associated with a range of commodities should be made here as should reference to any distinguishing marks stamped, branded, stenciled or labelled on them.

g. Ideally botanical names of tree species should be stated here when they are known. In practice it is acceptable to state softwood (coniferous) or hardwood (non coniferous).

h. The country where the wood material was grown/originated from if known

i. The serial number(s) of phytosanitary certificates issued in the country of origin (if applicable). This section should only be completed when reforwarding certificates are required e.g. when imported consignments of sawn timber are being re-exported.

j. The dimensions or weight of either the individual wood packaging articles or the volume of timber used to construct them. If the actually commodity being transported is wood e.g. sawn timber or logs then state the quantity in cubic metres for example.

k. The name of the sea vessel or the aircraft flight number if these are known. Alternatively simply enter air or sea freight.

Part 5 - ‘Special Conditions (including disinfestation and/or disinfection treatment) - enter

a. The wood treatment type eg Heat treatment, Chemical Pressure Impregnation (CPI), Fumigation, Kiln Dried (>20%) etc.

b. The name of the chemical or fumigant used eg Copper Chrome Arsenic (CCA), Methyl bromide etc.

c. The duration and temperatures required for effect treatment for relevant treatment type eg heat treatment = 30 minutes and 56˚c at core, Methyl bromide fumigation = 16 hours at 21˚C, Vacuum Pressure Impregnated = 8 hours at 25˚C etc.

d. The dosage rate of chemical or fumigant eg Methyl bromide fumigation = 64g/m3, Copper Chrome Arsenic (CCA) = 0.32% etc.

e. The date on which the treatment was performed.

f. The details of any other additional information which in your opinion is technically justified and relates to the wood packaging or sawn timber which is the subject of phytosanitary control.

http://www.forestry.gov.uk/pdf/guidancephytoapps.pdf/$FILE/guidancephytoapps.pdf


33

6.5 Comparison of strength grades

The following chart is based on a report called “International Grading Comparison.” The full report should be available here and only deals with comparisons of standards to South African standards:

http://www.timbersa.com/ICD/GradingComparison/gradingcomparison.asp

It is important to note that comparing stress grades (which help to define the strength of timber) between countries is extremely difficult due to the fact that different countries use different tests in order to classify timber and these tests are not necessarily comparable.

The table here is therefore only a rough guide since all the standards compare to the South African standard rather than each other (e.g. just because both the Australian F8 standard and the British SC8 standard both correspond the South African S10 standard, they do not necessarily correspond with each other.

S50

S45

S40

S35

No S

A e

quiv

alen

t

S30

C40

F14

No.

1,

2,

3,

Const

, Std

and U

til

S27

S24

C35

F11

SC9

S22

C30

S10

S20

C27

F8

Engin

eering

SC8

S18

C24

S16

C22

SC7

S7

S14

C18

F7

No.1

SC6

No m

atch

S12

C16

F5

SEL

(J&

P)

S5

S10

C14

F4

No.

2

SEL

(SLF

)

SC5

SC4

SC3

SC2

No S

A e

quiv

alen

t

SC1

So

uth

A

fric

a

ISO

Eu

rop

ean

Au

stra

lian

New

Z

eala

nd

Bri

tish

US

/C

an

ad

a




34

6.6 Safe stacking of sawn timber

This is reproduced from the Health and Safety Executive (UK) leaflet entitled ‘Safe stacking of sawn timber and board materials’. http://213.212.77.20/pubns/wis2.pdf

6.6.1 Stack stability factors

Consider the following as part of your risk assessment.

Ground and environmental conditions • Prepare the ground carefully where stacks are to

be assembled. It should be flat and even with a slope of no more than 2°, ideally with a top surface of asphalt, tarmac or concrete, and well maintained with no potholes.

• The ground should be strong enough to withstand the load of both stacks and machinery, be well consolidated, and its stability should not be affected by weather conditions such as heavy rain. Good drainage should be provided.

• Clear any obstacles such as waste timber or unused bearers from the stacking area as they may make stacks unstable.

• Stacks which are outside may be affected by wind, so where possible construct them so a small cross-section is facing the prevailing wind direction. Check external stacks after high winds. Securely attach any protective sheeting.

Bearers Bearers support packs of timber, keeping them off the ground and allowing space for fork-lift trucks to lift the pack. They also support the timber within the pack.

• Select bearers carefully. Ideally they should be straight and identical in length and cross-section (preferably square). If they are rectangular in section they are most stable when the long edge is horizontal.

• The length of the bearer should be equal to the width of the pack. If too long they protrude, encouraging climbing of the stack, or can be easily struck by passing vehicles. Short or offset bearers do not fully support the pack above and increase the load on banding.

• Bearers should be in good condition and should be destroyed if rotten, damaged or split. They should be made of a material strong enough to withstand the environment where the stack is constructed.

• Position bearers carefully to prevent timber in the supported pack from sagging and to avoid offsets in the stack. ‘Figure 21: Offset bearer’ shows the effect of a short or offset bearer. The tip line of the stack moves inwards from the edge since part of the width of the stack is not supported.

The same problem occurs if bearers are placed to run the length of the pack as shown in ‘Figure 22:

Figure 21: Offset bearer

Figure 22: Supported width

http://213.212.77.20/pubns/wis2.pdf


35

Supported width’. In this case the supported width of the pack is from the outside edge to outside edge of the bearers and the stack is less likely to be stable.

6.6.2 Banding

HSL Research Report ME/98/212 gives full details about banding of sawn timber and these are summarised in the following points:

• Before banding look at the requirements of the band and what will happen to the banded pack.

• Consider whether the timber is likely to expand or contract due to the surrounding storage conditions or treatment (ie timber with a high moisture content will shrink and the banding may come loose and need to be reapplied).

• Select a banding material that is suitable for the demands to which it will be subjected. For example, 12 mm wide polypropylene banding should not be used to band timber packs with cross-sections of greater than 0.5 m2 and masses greater than 400 kg. Use polyester or steel instead.

• To ensure a tight and secure pack is achieved, assemble packs carefully, minimising the space between timber.

• Take care when applying bands. Apply them squarely (ie parallel to the plane of the end face) close to columns of sticks within the pack. They should be tight to the face of the pack and not be applied over the ends of protruding sticks or bearers. Banding fasteners also need to be suitable for the pack and banding material.

• Wear eye protection when banding is being removed. When cutting tensioned metal banding, use safety cutters.

• Periodic inspection will highlight deficiencies in the banding, for example, loose bands and loss of pack shape. If problems are detected, the packs concerned should be rebanded or the banding retensioned. If the same problems occur on a regular basis, the type of banding being used should be reviewed, for example, a stronger band may be needed or a different type of fastener.

6.6.3 Pack characteristics

• Individual packs of sawn timber are the building blocks of the stack. Generally, good packs make good stacks.

• Where possible the timber in the pack should all be of the same cross-section and length. Do not leave timber protruding from the end faces of the pack for the purpose of climbing the stack.

• Out-of-square or lozenge-shaped packs affect the stability of the stack and cause an increase in tension in the banding material.

• Packs can also ball or roll, moving the tipping line inwards, having the effect of reducing the width of the pack (ie only part of the width of the pack is supported). This makes the stack far less stable.

• Do not stack collapsed or partially collapsed packs or transport them off site - reassemble them. If identified in a stack, remove and rectify them using an established safe system of work.

• Keep the tops of packs level which will help to form a vertical stack. If the top row is not complete, any bearer placed on top should be flat and supported by timbers placed at the edge of the pack.

• Separating sticks (dunnage) can be beneficial within the pack, helping to form a tight square pack and preventing balling or rolling. Like bearers, stick length should equal pack width. Sticks may increase the tendency for the pack to lozenge and this should be monitored.


36

6.6.4 Stack height and stacking practices

• In an indoor environment, the maximum height of the stack should not be more than four times the shortest width of the pack (ie a ratio of 4:1). Outside where wind may affect the stack, the ratio should be reduced to 3:1.

• These ratios are general guidelines - the actual stacking height should be determined after considering the results of your risk assessment. For example, where there is a risk of vehicle strikes against the stack, the stack is on a slope of more than 2°, or there is frequent public access, then the ratios should be reduced to 3:1 indoors and 2:1 outside. However, if these and other risks are absent (eg in a tightly packed kiln or outside on level concrete in a sheltered area) these ratios may be increased.

• Short or offset bearers, and balled or rolled packs, may result in the supported width of the stack being less than it appears and the stack height should be reduced. See the ‘Bearers’ and ‘Pack characteristics’ sections.


37

6.7 Container sizes

Taken from UNJLC field manual 10

45' H

igh C

ube

32,5

00 k

g (

71,6

56 lb.)

4,7

40 k

g (

10,4

49 lb.)

27,7

60 k

g (

61,2

00 lb.)

45' H

igh C

ube

13,7

16 m

m (

45'-

0")

2,4

38 m

m (

8'-

0")

2,8

96 m

m (

9'-

6")

45' H

igh C

ube

13,5

56 m

m (

44'-

6")

2,3

52 m

m (

7'-

6")

2,7

00 m

m (

8'-

10")

45' H

igh C

ube

2,3

40 m

m (

7'-

6")

2,5

85 m

m (

8'-

4")

45' H

igh C

ube

86 m

³ (3

,037ft

.³)

40' H

igh C

ube

30,4

80 k

g (

67,2

00 lb.)

3,7

30 k

g (

8,2

23 lb.)

26,7

50 k

g (

58,9

76 lb.)

40' H

igh C

ube

12,1

92 m

m (

40'-

0")

2,4

38 m

m (

8'-

0")

2,8

96 m

m (

9'-

6")

40' H

igh C

ube

12,0

32 m

m (

39'-

1")

2,3

52 m

m (

7'-

6")

2,6

95 m

m (

8'-

7")

40' H

igh C

ube

2,3

40 m

m (

7'-

6")

2,5

85 m

m (

8'-

4")

40' H

igh C

ube

76.3

m³

(2,6

94.2

ft.³

)

40' Sta

ndar

d

30,4

80 k

g (

67,2

00 lb.)

3,5

30 k

g (

7,7

82 lb.)

26,9

50 k

g (

59,4

17 lb.)

40' Sta

ndar

d

12,1

92 m

m (

40'-

0")

2,4

38 m

m (

8'-

0")

2,5

91 m

m (

8'-

6")

40' Sta

ndar

d

12,0

32 m

m (

39'-

1")

2,3

52 m

m (

7'-

6")

2,3

90 m

m (

7'-

8")

40' Sta

ndar

d

2,3

40 m

m (

7'-

6")

2,2

80 m

m (

7'-

4")

40' Sta

ndar

d

67.6

m³

(2,3

86.1

ft.³

)

20' Sta

ndar

d

30,4

80 k

g (

67,2

00 lb.)

2,2

00 k

g (

4,8

50 lb.)

28,2

80 k

g (

62,3

50 lb.)

20' Sta

ndar

d

6,0

58 m

m (

19'-

10")

2,4

38 m

m (

8'-

0")

2,5

91 m

m (

8'-

6")

20' Sta

ndar

d

5,8

98 m

m (

19'-

2")

2,3

52 m

m (

7'-

6")

2,3

90 m

m (

7'-

8")

20' Sta

ndar

d

2,3

40 m

m (

7'-

6")

2,2

80 m

m (

7'-

4")

20' Sta

ndar

d

33.2

m³

(1,1

72.3

ft.³

)

RA

TIN

GS

Max

. G

ross

Wei

ght

Tar

e W

eight

Payl

oad

EX

TER

NA

L

DIM

EN

SIO

N

Length

Wid

th

Hei

ght

INTER

NA

L

DIM

EN

SIO

N

Length

Wid

th

Hei

ght

DO

OR

O

PEN

ING

S

Wid

th

Hei

ght

CU

BE

Cubic

Cap

acity

10 From UNJLC F.O.M. section 5.5 http://www.unjlc.org/field_manual/.. This specification is only a general description of containers.


38

6.8 Conversion table

Length

Metric to Imperial Imperial to Metric

1 cm = 0.394 inches 1 inch = 2.54 cm

1 m = 39.4 Inches 1 foot = 30.5 cm

1 m = 3.28 feet 1 foot = 0.305 m

1 m = 1.09 yards 1 yard = 0.914 m

1 km = 0.621 Miles 1 mile = 1.609 km

Weight


1 g = 0.035 ounces 1 ounce = 28.3 g

1 kg = 2.2 pounds 1 pound = 0.454 kg

1 tonne = 2200 pounds 1 Ton (US) = 1020 kg

Surface


1 cm2 = 0.155 Sq in 1 sq inch = 6.45 cm2

1 m2 = 10.76 sq ft 1 sq foot = 929 cm2

1 m2 = 1.2 sq yd 1 sq foot = 0.093 m2

1 ha = 2.47 sq acres 1 sq yard = 0.836 m2

1 km2 = 247 acres 1 acre = 0.405 ha

1 km2 = 0.386 sq miles 1 sq mile = 2.59 km2

Volume


1 cm3 = 0.061 cu inch 1 cu inch = 16.4 cm3

1 m3 = 35.3 cu feet 1 cu foot = 0.028 m3

1 m3 = 1.31 cu yd 1 cu yard = 0.765 m3

Temperature


(Celsius x 1.8) + 32

= Fahrenheit (Fahrenheit – 32): 9 x 5 = Celsius


39

6.9 Measuring moisture content

Moisture content is calculated by comparing the weight of a length of timber to its weight when it is ‘oven-dry’. The difference is the amount of moisture contained in the timber. Moisture Content (MC) is the percentage of moisture in timber. Timber is ‘oven-dry’ once it has achieved a constant weight in a ventilated oven of about 100 degrees Celsius (100˚C). The moisture content is then calculated using the following formula:

Weight of the length of timber before oven-drying = X

Weight of the timber after oven-drying = Y

Difference between weights = Z

Moisture content = Z / Y * 100

Ex. Weight timber before oven-drying

Weight timber after oven-drying

Diff. in weight

% moisture content

Timber type

X Y Z Z/Y*100 A 10.0 kg 8.8 kg 1.2 kg 13.6% Acceptable MC for dried timber B 11.2 kg 8.8 kg 2.4 kg 27% High moisture, open to attack C 17.0 kg 8.8 kg 8.2 kg 93% Green, recently felled

In the field, moisture content can be measured by drying a sample of wood in an oven set to around 100°C and weighing it repeatedly until it loses no further weight. A microwave can also be used for drying if there is one available.

Electric moisture meters can be used to measure moisture. They come in two types – resistance meters (which have two metal pins) and dielectric meters (which have a flat plate). Meter readings will need to be corrected for the species and air temperature, though some meter can do this automatically instead of the measurer having to do this by hand.

More advanced meters can also download information to a computer, though this would only be necessary for a large quality control program.

When using electric meters it is important to measure across the grain and push the spikes in the correct depth. Several readings, from randomly selected pieces of wood should be made.


40

6.10 Timber treatments requiring expert handling (New Zealand)

This is taken from Best Practice Guideline for Safe Use of Timber Preservatives published by New Zealand Timber Preservation Council Inc11.

The following table contains a list of timber preservatives and antisapstains that trigger HSNO approved handler and tracking requirements due to either a 6.1A, 6.1B or 6.1C classification (as at 1 October 2004).

These products are required to be under the control of an approved handler at all times, irrespective of quantity. 12

Timber preservatives Antisapstains Ayrton C Oxide Antiblu CC CCA Oxide Antimould Booster Impretect C Antisapstain 550 CC Impretect Oxide Blue Control TCPN Mokubo AAC Busan 30 L Organotect Busan 30 WB Permacure Oxide Liquor Chlorocarb Polesaver Rods Cleanwood Protim 235 WR Hylite 109 Protim 95WR Hylite Antimould Rentokil CCA 60% Nexgen Sarmix 3 NP-1 (Kop-Coat) Sarmix Oxcel C NP-1 (Koppers Arch) Tanalith Antimould NP-1 Plus Tanalith AWPA C 60% Prosan 17 Tanalith C 60% Sabre Tanalith C Oxide 60% Sentry Tanalith E Taratek 5F Tanalith NCA 50% Taratek CC Taratek LVL Taratek DC TimTech C Oxide Taratek GC TimTech C Salt Taratek GP TimTech N Taratek IG Vacsol Antimould Taratek PC Vacsol Clear Timber Antisapstain Guard Vacsol N Tolcide MW10 Woodserve Preservation Gel Tuff Brite C

11 New Zealand Timber Preservation Council (No date) Best Practice Guideline


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6.11 FSC certified forests

Downloaded from: http://www.unep-wcmc.org/forest/ffl/fis/fsc_small.htm

http://www.unep-wcmc.org/forest/ffl/fis/fsc_small.htm


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6.12 References and further reading / resources Corsellis, T. & Vitale, A. (2005) Transitional Settlement of Displaced Populations, Oxfam, Oxford.

[http://www.sheltercentre.org/shelterlibrary/items/pdf/Transitional_Settlement_Displaced_Populations_2005.pdf]

Davies, J. and Lambert, R. (2003) Engineering in Emergencies, RedR, U.K.

HSE (2001) HSE Information Sheet: ‘Safe stacking of sawn timber and board materials’ Woodworking Sheet No 2 (revised), Health and Safety Executive (UK). http://213.212.77.20/pubns/wis2.pdf

HSE (2003) HSE Information Sheet: ‘Toxic Woods’ Woodworking Sheet No 30, Health and Safety Executive (UK). http://www.hse.gov.uk/pubns/wis30.pdf

Janssen, J. (1995) Building with Bamboo: An Introduction, ISBN 1 85339 203 0, published by ITDG Development Bookshop, 103/105 Southampton Row, London, WC1B 4HH, UK.

Jayanetti, L. & Follett, P. (2000) Timber Pole Construction: An Introduction, London. ISBN 1 85339 502 1, published by ITDG Development Bookshop, 103/105 Southampton Row, London, WC1B 4HH, UK.

Kuru, G. (2005) Development and Implementation of a Wood Procurement Plan for Post–Tsunami Reconstruction in Indonesia, FAO. http://www.fao.org/forestry/webview/media?mediaId=10473&langId=1

New Zealand Timber Preservation Council (No date) Best Practice Guideline for the Safe Use of Timber Preservatives and AntiSapstain Chemicals http://www.osh.govt.nz/order/catalogue/timberpreserve.shtml

Stulz, R. and Mukerji, K. (1993) Appropriate Building Materials – A Catalogue of Potential Solutions, ITDG, U.K.

The Sphere Project (2004) Humanitarian Charter and Minimum Standards in Disaster Response, The Sphere Project 2004. http://www.sphereproject.org

The Roundwood Haulage Working Party (2002) Road Haulage of Round Timber Code of Practice, http://www.confor.org.uk/timber_transport/pages/case_download.asp / http://www.ukfpa.co.uk/pdfs/CODE_OF_PRACTICE_2003.pdf

Timber Trade Federation (TTF) (2004) TTF Public Summary of the Tropical Forest Trust (TFT) Scoping Study: Sourcing Legal Timber from Indonesia, 28 April 2004. [http://www.illegal-logging.info/papers/Sourcing_Legal_Timber_from_Indonesia.pdf]

UN FAO (2005a) “Facilitation of wood supply for Post Tsunami Reconstruction A meeting facilitated by UN-FAO For NGO’s 22 July 2005” by George Kuru, UN-FAO Wood Supply Consultant [http://www.humanitarianinfo.org/sumatra/reliefrecovery/cross/docs/UNFAOPresentationToNGOsFacilitationOfWoodSupplyForReconstruction-220705.pdf]

UN FAO (2005b) Guidelines for Timber Classification and Usage in Post–Tsunami Reconstruction - Draft Discussion Documents, UN FAO, 26 July 2005.

UNHCR (2005) Environmental Guidelines, Environment Technical Support Section, UNHCR Geneva and IUCN, August 2005 http://www.unhcr.org/cgi-bin/texis/vtx/protect/opendoc.pdf?tbl=PROTECTION&id=3b03b2a04

UNIDO (1995a) Timber Construction for Developing Countries – Structural Timber and Related Products, UNIDO. ISBN 92-1-106286-1

UNIDO (1995b) Timber Construction for Developing Countries – Introduction to Wood and Timber Engineering, UNIDO. ISBN 92-1-106278-0

USDA Forest Products Laboratory (1999) Wood handbook—Wood as an engineering material, U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. Rep. FPL–GTR–113. Madison, WI, USA. http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm

6.12.1 Useful websites Office of the UN Recovery Coordinator for Aceh and Nias (Timber page): Documents (included in the list above)

related to timber issues in Indonesia. www.humanitarianinfo.org

Shelter Centre works with all stakeholders in the shelter sector to improve capacity, coordination and good practice: www.sheltercentre.org

Timber Research & Development Association (TRADA): http://www.trada.co.uk/. Also provided technical information for: www.timberbestpractice.org.uk/. Also has a species database: www.trada.co.uk/techinfo/tsg/

Timber Building in Australia: Excellent technical documents and glossary etc. http://oak.arch.utas.edu.au

National Timber Education Program (Australia): www.timber.org.au/ (Educational Resources). Useful timber manual: www.timber.org.au/resources/Revised%20P1.pdf

Timber Net Australia has a limited species guide: www.timber.net.au/species/

WWF Forest Conservation Program: Includes a manual on legal timber purchases www.panda.org/

International Tropical Timber Organization: Includes guidelines for forest management. www.itto.or.jp

Ecoport: database for help identifying plants and animals. http://ecoport.org/ep

http://www.sheltercentre.org/shelterlibrary/items/pdf/Transitional_Settlement_Displaced_Populations_2005.pdf

http://www.sheltercentre.org/shelterlibrary/items/pdf/Transitional_Settlement_Displaced_Populations_2005.pdf

http://213.212.77.20/pubns/wis2.pdf

http://www.hse.gov.uk/pubns/wis30.pdf

http://www.fao.org/forestry/webview/media?mediaId=10473&langId=1

http://www.osh.govt.nz/order/catalogue/timberpreserve.shtml

http://www.sphereproject.org/

http://www.confor.org.uk/timber_transport/pages/case_download.asp

http://www.ukfpa.co.uk/pdfs/CODE_OF_PRACTICE_2003.pdf

http://www.illegal-logging.info/papers/Sourcing_Legal_Timber_from_Indonesia.pdf

http://www.illegal-logging.info/papers/Sourcing_Legal_Timber_from_Indonesia.pdf

http://www.humanitarianinfo.org/sumatra/reliefrecovery/cross/docs/UNFAOPresentationToNGOsFacilitationOfWoodSupplyForReconstruction-220705.pdf

http://www.humanitarianinfo.org/sumatra/reliefrecovery/cross/docs/UNFAOPresentationToNGOsFacilitationOfWoodSupplyForReconstruction-220705.pdf



http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm

http://www.humanitarianinfo.org/sumatra/reliefrecovery/cross/list.asp?id=6

http://www.humanitarianinfo.org/

http://www.sheltercentre.org/sheltercentre/index.htm

http://www.trada.co.uk/

http://www.timberbestpractice.org.uk/

http://www.trada.co.uk/techinfo/tsg/

http://oak.arch.utas.edu.au/glossary/view_glossarylist.asp?term=T

http://oak.arch.utas.edu.au/

http://www.timber.org.au/

http://www.timber.org.au/resources/Revised P1.pdf

http://www.timber.net.au/

http://www.timber.net.au/species/

http://www.panda.org/about_wwf/what_we_do/forests/index.cfm

http://www.panda.org/

http://www.itto.or.jp/live/index.jsp

http://www.itto.or.jp/

http://ecoport.org/ep