t h e bu i l d e r ’s gu i d e t o t imbe r i n c on s t r u c t i on .

contents .

A sustainable building material 3

Why choose wood? 4

Standard sizes, Building Regulations and Grades 5

Markings 6

Softwood and strength classes C14-30 7

Hardwood and strength classes D30-70 8

Treatment 9/12

Studding 13

Roofing 14

Joists 15/16

Timber frame 17/18

Trussed rafters 19/20

Engineered timber beams 21/22

Engineered wood 23/24

Decking 25/26

Cladding 27/28

Joinery timber 29

Marine use 30

Suppliers and information 31/32

21

wood for good is a generic wood campaign sponsored byThe Swedish Timber Industry, the Forestry Commission,ConFor (The Confederation of Forest Industries) and theNorthern Ireland Forest Service. All members are committedto sustainable forest management. In each of the members’countries credible third party certification schemes are nowoperating and increased areas of forest are being certified.

Visit www.woodforgood.com for more information and fordetails of seminars, exhibitions and downloads of thefollowing publications:

• Tackle Climate Change: Use Wood• Climate Change Factsheets (9)• Building Sustainably with Wood. EcoHomes 2006 version• Building Sustainably with Wood. Case Studies• Wide Span Wood Sports Structures• Large Span Timber Structures• Innovation and Sustainability. Wood Products for Architects• Builder’s Guide to Timber in Construction• Builder’s Guide to Plywood• Builder’s Guide to Timber in Joinery• Builder’s Guide to Solid Wood Flooring• Factsheets (Flooring, Cladding, Costructional Timber,

Glulam & LVL, Windows & Conservatories, Doors,Mouldings, Climate Change, Decking, Engineered WoodProducts, Lofts, Plywood, Timber frame, Finishes)

• David Domoney’s Garden DIY Book• Michael Jewitt’s DIY Wood Cookbook

There is increasing pressure on architects and builders fromnational and local government to reduce the impact ofbuilding and construction on the environment.

One answer is to use more wood, the most environmentallyfriendly commercial building material available.

It is naturally renewable, with a significant surplus ofproduction over harvest in Northern Europe.

It helps limit the growth of global warming, as growing treesabsorb CO2 and produce the oxygen we breathe; it requireslow energy inputs to harvest, transport and mill; and it canbe recycled and then eventually burned for energy as asubstitute for fossil fuels.

Well managed forests – managed with care for theenvironment and future generations – are typical of the UK,Nordic countries, Europe, Canada and the United States.

For additional reassurance, look for independent certificationby, for example, the Forest Stewardship Council (www.fsc-uk.info) or Pan-European Forestry Certification(www.pefc.co.uk).

a s u s t a i n ab l e bu i l d i n g ma t e r i a l .

3 4

Energy required to produce one tonne of building material

source: Centre for Alternative Technology

Timber2000

kW/HRS

Aluminium25000

kW/HRSPVC

45000kW/HRS

Steel13000

kW/HRS

why choose wood?

• Simplicity of use

• Value for money

• High strength-to-weight ratio: strength for strength, pineand spruce are 16 times lighter than steel, 5 times lighterthan concrete

• Low thermal conductivity: 12 times better than concrete,400 times better than steel, 1,500 times better thanaluminium

• Stable performance in fire: when timber burns it buildsup a protective char layer which insulates the remainingsection; this and its low co-efficient of expansion meanits mechanical properties are less affected by fire thanother materials like steel, which can buckle and collapse

• Good sound absorption

• Non-toxicity

• Recyclability

• Sustainability. It comes from trees – a renewable resource.

markings .

There is a standard marking system for timber produced inthe UK for our construction industry, which is also used onimports from Scandinavia, mainland Europe, Canada andthe USA. It allows you and building inspectors to checkthat the correct timber is being used for any particular job.

Softwood within BS 4978 : 1996 has two descriptions:• GS (General Structural)• SS (Special Structural)

Hardwoods are graded within BS 5756 : 1997 into 3 types:• HS (Tropical Hardwoods)• THA/THB - referring to timber with a cross section of

20,000mm2 or more and a thickness of 100mm or more• TH1/TH2 - referring to timber with a cross section of less

than 20,000mm2 and a thickness less than 100mm

bui ld ing regula t ions and g rades .

The use of timber for construction in the UK is controlledby the Building Regulations and covered in BS 5268.

When you use timber in construction, ensure it is strength-graded and clearly marked: the timber will be qualitycontrolled and compliant with the Building Regulations.

In the UK, all structural timber is strength-graded, eithervisually or by machine, with third party control approved bythe UK Timber Grading Committee.

BS 4978 1996 covers visually graded softwoods.

BS EN 519 1995 covers machine graded softwoods.

BS 5756 1997 covers hardwoods.

Timbers with similar strength properties are grouped intostrength classes to make it easier to see which species arebest for which applications.

Grades C14 to C40 show which softwood species apply inwhich grade.

Grades D30 to D70 apply to hardwoods.

The higher the number, the stronger the grade.

Moisture content also needs to be taken into account as itaffects the stability of the timber.

For further information on Codes and Grades contactTRADA at www.trada.co.uk.

55 6

genera l s tandard s izes (planed s izes in brackets)

Pine Spruce

hardwood spec ies which sa t i s fy the requi rements for s t rength clas ses D30-D70.

sof twood spec ies which sa t i s fy the requi rements for s t rength clas ses C14-C30.

7 8

Tables courtesy of TRADA

Preservative treatments.

There are 3 basic types of preservative treatments: waterborne, organic solvent and tar oils.

Waterborne: Waterborne wood preservatives use water as the carrier to take the activeingredients into the timber.

Organic: Organic solvent-based preservatives use white spirit or petroleum distillate as acarrier for the active ingredients, in the same way that water-soluble types use water as thecarrier.

Tar: Tar oils are blends of distillate oils, mainly from coal tar with a boiling range form200°C to 400°C.

The only tar oil used for preservation is Creosote, an oil-type preservative which is insolublein water, resistant to leaching and does not cause wood to swell during treatment.

It protects against decay, insect and borer attack and is a brownish-black oil composed ofhundreds of organic compounds by distilling coal tar. Creosote treatment gives wood a darkbrown to black colour and is used extensively in treating poles, sleepers and bridge timbers.

Waterborne preservatives are soluble in water during treatment. Fixed preservatives reactchemically to form insoluble compounds that bond to the wood. Subsequent rewetting ofthe wood will not cause preservative loss. Unfixed compounds do not bond with the woodand should not be used in areas where timber will be permanently wet.

The most commonly used waterborne preservatives are based on copper plus organicbiocides. These are classified as fixed and are used to protect timber from all majorbiodeteriogens including decay fungi, wood boring insects and termites. Applications rangefrom decks to wood-frame houses.

Borates are another type of waterborne preservative providing effective protection againstattack by wood boring insects. They are applied either by a diffusion process or by a vacuumpressure process that delivers boron relatively deeply into the timber. The boron is not fixedin the timber and can therefore leach out, restricting boron-treated timber to interior usessuch as flooring and framing.

t rea tment .

Why preservative treat wood?

No timber is totally immune to deterioration if exposed, over a sufficient period of time,to one or more of the agents that can cause timber to degrade.

Wood protection involves the removal or control of one or more of these agents byintroducing various approved chemicals into the timber. Other methods of woodenhancement by molecular alteration and heat treatment also help preserve timber.

In order to gain approval, preservatives must be tested in accordance with BS EN 599-1 to determine levels of effectiveness for particular areas of

use. In the UK, these tests are laboratory-based.

Industrial treatments.

Industrial pre-treatment is the most effective method of protecting timber. The main twoprocesses are carried out in enclosed systems.

Double Vacuum or Low Pressure Treatment: used for timbers destined for Use Class 1-3A.Treatment provides an effective ‘envelope’ protection around the timber. Some companiesuse a colour tint that identifies the timber as being treated.

Vacuum Pressure or High Pressure Treatments: suitable external applications, both in andout of ground contact. Preservative enters the celluar structure and gives the timber a greencolouration. For landscaping applications, a brown colouration and water repellant can beadded.

Whichever process is used, the UK utilises new generation preservatives based on the latestbiocidal technologies, providing an appropriate timber protection. For the doublevacuum/low pressure treatment, there is a choice of water solvent based systems. Vacuumpressure/high pressure treatments are all water-based and utililse copper as the mainingredient combined with organic secondary biocides.

Use classes help us to identify where natural durability is not enough. In such cases,preservative treatment is a must to protect wood from bio-degradation.

9 10

Acetylated wood.

Although it is only now becoming available to consumers, acetylation, a process usingnaturally occurring acetic acid to modify the molecular structure of the wood, is founded onmore than 75 years of scientific investigation and 13 years of process and productdevelopment. The process is effective throughout the section of treated timber providingdurability (it can achieve Class 1) and enhanced stability.

Known as Accoya™, and available in the UK solely through BSW , it is suitable for exteriorjoinery products, with a life of at least 60 years above ground and 25 years in-ground. Itsexcellent stability and UV resistance allow coatings to require significantly reduced coatingsmaintenance.

Wood redefined.

Derived from faster growing temperate climate woods, Accoya is equivalent to a ‘new species’of wood:

• ‘Class 1’ durability – the most demanding, suitable for outdoor use

• Dimensional stability – swelling and shrinkage are minimized, providing better paintadhesion and extending maintenance intervals

• Reliability – consistent quality of process

• Environmental compatibility – non-toxic, recyclable

• Sustainability – uses woods from managed forests and plantations

Which products should use Accoya?

Accoya is expected to be used in any application where a material requires durability andstability – from ordinary uses, such as decks, doors, windows, canal linings, garden furnitureand cladding, to uses previously considered challenging, like road bridges, sound barriers,road signs and bathroom floors. Visit www.bswaccoya.co.uk or www.bsw.co.uk

Osmose Indurite Advanced.

Osmose have developed a product called Osmose Indurite Advanced which uses a water-based impregnation system and a modified natural polysaccharide similar to wood’s owncellulose, to endow softwoods with the hardness and strength of hardwoods. It is suitable forindoor products like flooring, furniture, doors and windows. Visit www.osmose-europe.com

Use Use Principal Typical Service Situation Examples class Biological Agency

1 Above ground, Insects Internal with no risk of All timbers in normal pitched roofscovered. wetting or condensation. except tiling battens and valleyPermanently dry. gutter members. Floor boards,Permanently <18% architraves, internal joinery, skirtings.moisture content. All timbers in upper floors not

built into solid external walls.

2 Above ground, Fungi insects Internal with risk of Tiling battens, frame timbers incovered. Occasional wetting or condensation. timber frame houses*, timber inrisk of wetting. pitched roofs with high condensationOccasionally >20% risk, timbers in flat roofs, groundmoisture content. floor joists*, sole plates (above dpc),

timber joists in upper floors builtinto external walls.

3 Above ground, not Fungi A – External, above damp External joinery including roof soffitscovered. Exposed proof course (dpc) – and fascias, bargeboards etc. to frequent wetting. coated. cladding, valley guttering timbers. Often >20% Fence rails, gates, fence boards, moisture content. B – External, above damp deck boards and balustrades,

proof course (dpc) agricultural timbers not in– uncoated. soil/manure contact.

4 In contact with Fungi A – Soil contact. Fence posts, gravel boards, deckground or fresh Timbers in permanent supports, agricultural timbers inwater. Permanently contact with the ground soil/manure contact, poles, sleepers,exposed to wetting. or below dpc. playground equipment, motorway Permanently >20% and highway fencing, sole platesmoisture content. B – Fresh water contact. below dpc.

Timbers in permanentcontact with fresh water. Lock gates, revetments.

Permanently >20% moisture content. C – Cooling tower packing. Cooling tower packing (fresh water).

Timber exposed to theparticularly hazardousenvironment of coolingtowers.

5 Permanently Marine borers All components in Marine piling, piers and jetties, dockexposed to sea permanent contact gates, sea defences, ships’ hulls,wetting by salt with sea water. cooling tower packing (sea water).water.

Permanently >20% Fungimoisture content.

1211

* These timbers are assigned to a higher use class than suggested by their location in the structure, owing to the potential consequences of failure based on experience within the UK.

roofing.

Use kiln dried softwood from C16 to C24.

It may be necessary to use a higher strength class or specialstructural grade for some larger load-bearing sections.

Always check the grade and strength before using timber forstructural purposes.

Tiling battens, generally from lower grades of pine andspruce, should be treated with preservative and comply withBS 5534.

See later for Trussed Rafters.

13 14

s tudding.

Studding refers to small sectional timber used to constructframeworks for walls, ceilings and partitions.

The main species used in studding is spruce, which hasgood strength properties and can be supplied sawn orplaned. Planed is easier to handle and its consistentdimensions make fitting plasterboard and other sheetmaterials simpler.

Use strength class C16 kiln dried softwood.

BS EN 1313-1 : 1997 covers the range of softwood sizesproduced.

Typical sawn sizes:• 47mm x 75mm• 47mm x 100mm• 47mm x 150mm

Surfaced timber, or CLS (Canadian Lumber Sizes) is widelyused for studding. It has 3mm radius eased edges andconsistent dimensions.

BS EN 1313-1 and BS EN 336 cover sizes for surfacedtimber.

Typical sizes are:• 38mm x 63mm• 38mm x 89mm• 38mm x 140mm

Lengths are generally from 1.8m to 6.0m or more, inincrements of 300mm, with the most common lengthsbetween 2.1m and 4.2m.

Regularised joists are machined to provide an accuratewidth (to 1mm of the original size) so as to make theapplication of floors and building-linked work moreconsistent.

Lengths range from 3.0m to 6.0m in 300mm increments.

For information about floor joists contact TRADA atwww.trada.co.uk

For information about laying solid wood or plywood flooringask for your free ‘Builder’s Guide to Solid Wood Flooring’.

f loor jo i s t s .

Use kiln dried softwood to strength grade C16.

The main species used is spruce, due to its strength,availability and low cost.

Use grade stamped timber that complies with BS 5268.Note that cutting the original size to a smaller section willinvalidate the grade stamp.

To extend use, specify pressure treated timber.

15 16

Tables courtesy of TRADA in conjunction with Eurocode 5

glulam.

Beams or columns made up from layers of parallel timberlaminates glued together under high pressure. LVL (laminatedveneer lumber) is similar but uses peeled veneers.

With a better strength to weight ratio than steel, attractivelooks and good environmental credentials, glulam beams areincreasingly used in large scale projects like bridges.

Benefits: • Large sections and long lengths for wide spans.• Beams can be shaped and curved to achieve arched roofs.• Greater regularity and stability.

Contact Finnforest at www.finnforest.co.uk, Moelven atwww.moelven.com or Merk at www.merk.de

Relax™ timber.

In conventionally dried timber, the moisture content in themiddle may be higher than at the surface. In Relax™ timber thecentre is targeted to a specific moisture content and the surfacesare equalised through adding steam in the kiln.

Benefits: • Greater stability, fewer defects, greater resistance to cupping.

Suitable for finished products like joinery items and mouldings.

Contact SCA at www.timberuk.sca.com

engineered wood.

heat treated wood.

Heat treated wood, or ThermoWood,® is softwood that has beentreated at temperatures up to 215oC to change the cell structureof the wood, reducing equilibrium moisture content by up to50%, expelling resin and breaking down the natural sugars.

Benefits: • The softwood timber becomes more durable and stable.• The process uses heat and steam and is chemical-free.• The timber is PEFC (Programme for the Endorsement of Forest

Certification).

Suitable for fencing, noise barriers, cladding, decking,windows, doors, garden furniture and many other productsaffected by harsh conditions.

Please note:• Use stainless/galvanised fixings.• Use annular ring shanked nails applied level to the board’s surface.• Can be fixed as normal timber, pre-drilling for screws. • UV light will grey ThermoWood®, as any timber. Various finishes,

including oil and water based stains, can be applied if required.

Contact Finnforest at www.finnforest.co.uk or Stora Enso atwww.storaenso.com

finger jointed timber.

Pieces of timber with machine cut interlocking fingers whichare glued and bonded together using high pressure machines.

Benefits: • Lengths of up to 12m of straight, knot-free wood with the same

strength as solid timber and reduced wastage.

Suitable for the construction of windows and door stiles.

Contact Södra at www.sodra.se23 24

moisture content reduced by up to 50%

wood becomes darker

bending strength reduced by 10 - 20%

splitting strength reduced by up to 50%

deformation reduced by up to 50%

resin removed

improved weather resistance

improved rot resistanceRelaxTM t imber

10% throughout

Moisture content

Moisture content

7% 10% 7%

Conventional t imber

‘ room in the roof ’ (RIR) t r usses .

RIR trusses create space for a ‘room in the roof ’ byproviding a roof structure without internal diagonalmembers.

With building space at such a premium, they are anincreasingly popular choice, offering significantly reducedbuilding costs per square metre.

Always check with planning authorities before proceeding.

There are many other trussed rafters types:Bobtail.A truncated normal triangular roof truss.Cantilever.A trussed rafter which extends beyond its support points.Assymetric.A truss with two rafters meeting at the apex, but withdifferent pitches on each side.Fink or Fan.The standard type. Rafters have the same pitch and websform a ‘W’ shape.Monopitch.A right angled triangular truss with one rafter.Girder.Two or more trusses bolted together, designed to carry aconcentrated or enhanced load.Hip Set.The trusses, girders and loose timber components neededto form a hip end.Pitch.The angle of the rafter to the horizontal, in degrees.Rafter.The uppermost member carrying the roof covering.

t r ussed ra f te r s .

Wooden trussed rafters are widely used in the UK house-building industry and increasingly popular in commercialand refurbishment projects.

These engineered roof structures are made from quality kilndried, strength-graded timber, joined with steel nailplatesapplied under high pressure. They make roof structuresquicker, easier and cheaper to erect.

Points to note:• Do not cut or alter trussed rafters without the approval of the

truss designer/supplier.• Ensure all water/storage tanks are properly supported in

accordance with the design.• Use correct roof bracing when installing the trusses. This

information will be contained in the roof design and is anessential part of the whole roof construction.

• When fixing trusses at bearing positions, always useproprietary truss clips - never nail through nail plates.

• Metal straps may be required for fixing down wallplates aswell as restraint straps for connecting masonry gables - consultyour local building inspector if unsure.

• Trussed rafters and roof bracing should always be installed inaccordance with the roof design plans/specification. If in anydoubt consult your truss supplier.

• For more information about supply and use of trussed rafters,contact the Trussed Rafter Association at www.tra.org.uk orcall 01777 869281.

19 20

A comprehensive range of sizes is available:

Engineered and pre-manufactured products are designed togive specific performances in structural applications. Greatcare should be taken when making alterations to the product.

Contact James Jones Ltd at www.jamesjones.co.uk, orFinnforest UK Ltd at www.finnforest.co.uk

eng ineered t imber beams .

Known as I-beams (or Finnjoists, marketed by Finnforest UK,or JJI joists, marketed by James Jones Ltd of Scotland),engineered timber beams are increasingly popular in bothhousebuilding and commercial sectors. Used in place oftimber joists, they contribute towards a standard buildingpackage solution that can also be compatible with pre-formedflooring solutions.

JJI joists are manufactured from kiln dried strength class C24softwood for the top and bottom members of the beam (orflanges) and from oriented strand board for the middle (web).

Finnjoists have flanges manufactured from Kerto LVL(laminated veneer lumber).

Benefits:• Superior strength-to-weight ratio, allowing longer spans and

easier handling.• Resistance to shrinking and warping contributes to creating

‘quieter’ flooring solutions.• Consistent dimensions for extra stability.• Easy to cut and drill, for plumbing and electrical installation

(see manufacturer’s recommendations).• Backed up by software and engineering support programmes,

simplifying planning and design and the supply of calculationsfor the authorities.

• Comprehensive technical literature available.

21 22

Examples from the Finnjoist range

Examples from the JJI range

glulam.

Beams or columns made up from layers of parallel timberlaminates glued together under high pressure. LVL (laminatedveneer lumber) is similar but uses peeled veneers.

With a better strength to weight ratio than steel, attractivelooks and good environmental credentials, glulam beams areincreasingly used in large scale projects like bridges.

Benefits: • Large sections and long lengths for wide spans.• Beams can be shaped and curved to achieve arched roofs.• Greater regularity and stability.

Contact Finnforest at www.finnforest.co.uk, Moelven atwww.moelven.com or Merk at www.merk.de

Relax™ timber.

In conventionally dried timber, the moisture content in themiddle may be higher than at the surface. In Relax™ timber thecentre is targeted to a specific moisture content and the surfacesare equalised through adding steam in the kiln.

Benefits: • Greater stability, fewer defects, greater resistance to cupping.

Suitable for finished products like joinery items and mouldings.

Contact SCA at www.timberuk.sca.com

engineered wood.

heat treated wood.

Heat treated wood, or ThermoWood,® is softwood that has beentreated at temperatures up to 215oC to change the cell structureof the wood, reducing equilibrium moisture content by up to50%, expelling resin and breaking down the natural sugars.

Benefits: • The softwood timber becomes more durable and stable.• The process uses heat and steam and is chemical-free.• The timber is PEFC (Pan European Certification System).

Suitable for fencing, noise barriers, cladding, decking,windows, doors, garden furniture and many other productsaffected by harsh conditions.

Please note:• Use stainless/galvanised fixings.• Use annular ring shanked nails applied level to the board’s surface.• Can be fixed as normal timber, pre-drilling for screws. • UV light will grey ThermoWood®, as any timber. Various finishes,

including oil and water based stains, can be applied if required.

Contact Finnforest at www.finnforest.co.uk or Stora Enso atwww.storaenso.com

finger jointed timber.

Pieces of timber with machine cut interlocking fingers whichare glued and bonded together using high pressure machines.

Benefits: • Lengths of up to 12m of straight, knot-free wood with the same

strength as solid timber and reduced wastage.

Suitable for the construction of windows and door stiles.

Contact Södra at www.sodra.se23 24

moisture content reduced by up to 50%

wood becomes darker

bending strength reduced by 10 - 20%

splitting strength reduced by up to 50%

deformation reduced by up to 50%

resin removed

improved weather resistance

improved rot resistanceRelaxTM t imber

10% throughout

Moisture content

Moisture content

7% 10% 7%

Conventional t imber

25 26

Site preparation.• Plan access for underground services before starting.• Use a weed suppressant membrane covered by gravel under

deck.• If the deck is adjacent to a house, ensure adequate drainage

away from the building.

Installation.• Leave a 6mm gap between boards to allow for swelling and

drainage, a 3mm gap where edges butt.• Pre-drill and countersink screws. For hardwood, drill holes

2mm oversize. • Sink nails or screws into the grooves, using a nail

punch/countersink bit, to allow good drainage.• Position fixings 15mm from board ends to avoid splits.• For sloping sites, use multi-levels, or cantilever the deck using

calculated supports.• For joists & ledgers, use sections 47mm x 150mm min.• Fix joists at 400/450 centres, ensuring they are level from the

ledger to the front frame joist.• Fit noggins between joists to prevent twist.• Use 100mm x 100mm timber for support posts.• Fix the wall ledger 10mm from the brickwork to allow

drainage. Do not bridge dpc level.• Stagger joints; ensure edges butt equally on the joist.• Support raised decks with structural posts set into concrete

foundations.

Railings.• Local building regs in England and Wales require 900mm

guardrails at ground level, 1.1m for decks above 600mm.• Space newel posts no more than 1.8m apart.• Space spindles with a gap of no more than 100mm.• Fix the bottom rail at least 80mm above the deck.

deck ing.

The installation of a deck should be well planned, andquality components used – look out for the ‘Deck Mark’logo, a quality assurance scheme offered by the UK TimberDecking Association, covering not only the timbercomponents, fixings and finishes, but also the installed deckitself, as long as ‘best practice’ construction methods havebeen followed. For more information contact www.tda.org.

Although not all decks require planning permission, it iswise to check with your local authority before startingwork, particularly if there are raised levels, or if the deckborders a neighbouring property.

Building regulations may also be needed and best practicemust be adhered to.

Stability is vital for raised or multi-level decks, so checkload and weight calculations with a structural engineer.

Where decks are built on to new build, structural calculationsmay be needed.

Fixing and products.• Ensure softwood timber is pressure-treated. Treat any cut or

drilled surfaces with preservative end-grain sealer.• Store timber undercover and dry before fixing.• Use annular ring nails or galvanised/stainless steel screws to

prevent rusting or marking – twice the length of the timberdepth.

• Use joist hangers/galvanised clips/annular ringnails/galvanised screws and ‘secret’ fixing clips to make joiningand fixing timbers easier.

• Use appropriate concrete foundations with specialist postshoe/holders.

t imber cladding.

A wide range of softwoods and hardwoods can be used forexternal cladding. Good detailing and, when necessary, theuse of suitable preservatives will ensure long life.

Suitable softwoods include Redwood, Whitewood, Larch andWestern Red Cedar. Generally, softwood should be pressuretreated, although Larch and Western Red Cedar can be useduntreated if the sapwood is excluded.

Ultra violet light will bleach wood to a grey colour if it isnot protected by a pigmented coating. Oak and Western RedCedar (with the sapwood excluded), for example, are oftenleft without a coating to ‘weather’ naturally. This can also bedone with other preservatively treated softwoods.

Exterior stain finishes are used to maintain or change theoriginal colour and can, in combination with different boardprofiles, be used to create many different effects.

For more information, TRADA publishes a design guide onExternal Timber Cladding - visit www.trada.co.uk

Tips:• Ensure any cut ends of cladding are treated with preservative.• Fix onto pre-treated battens.• Battens to be at least 38mm wide, 19mm thick and fixed

at 600mm centres.• Ensure joints meet centrally on a batten.• Allow for draining and ventilation in the cladding.• Use timber at least 150mm wide.• Use tongued and grooved (with the tongue installed

uppermost) or rebated cladding for vertical installation.• Use shiplap style cladding for horizontal installation.• Always base-coat the back of the cladding before fixing.• Consult BS EN 350 for durability of specific species.

27 28

29 30

jo iner y t imber.

Please see your free ‘Builder’s Guide to Timber in Joinery’for detailed information on windows, doors, panelling,mouldings, flooring, conservatories etc.

windows and conservatories.

Reacting to the loss of market share to PVC-U in the ‘80sand ‘90s, the wood industry has worked hard to addressdurability and performance, with suppliers and manufacturersco-operating to produce highly durable finished timberproducts backed by performance guarantees. This has resultedin a significant and sustained increase in market share.

Modern wood windows can come fully-finished, readydouble-glazed, with excellent security features.

The Timber Window Accreditation Scheme operated by the British Woodworking Federation offers a minimumpaint finish guarantee of 8 years and a timber guarantee of30 years. See www.bwf.org.uk for details of their windowsand fire door schemes.

t imber in mar ine use .

Timber is used in many marine applications in addition tomarine quality plywood used in boat construction.

It is used to form sea defences and as piling for maintenancework, as well as to create the decks, walkways and bridgesthat form an important part of the marine environment ofmany new developments.

It is important to use the correct species if in contact with the water and to consider bio-hazard problems whenspecifying treatments. For advice contact TRADA atwww.trada.co.uk.

As in any structural application, ensure that the timbermeets the specific regulation requirements.Oak European. Should be treated.Elm Dutch. More durable than English.Larch European. Strong and heavy.Hemlock Alaskan/Canadian/American.

Should be treated.Douglas Fir Canadian/British Columbian.

Should be treated.Scots pine British/European. Should be treated.Iroko African. Very strong and durable.Keruing Asian. Quite durable.

Treat for extended life.Purpleheart Tropical American.

High strength – used in bridges.Greenheart Guyanan. Strong and durable.

wood. for good. only promotes timber from well-managedsources. Always check with your supplier that the species youchoose is produced from well-managed forests.

BWF ACCREDITED TIMBER WINDOWBWF101 - E123456

Window ManufacturerTel: 09876 543210

IMPORTANTDO NOTREMOVE

OR DEFACELABEL

Fully FactoryFinished &

Factory GlazedE

In partnership withBSI Product Services

for fur ther infor mat ion .

The British Woodworking Federation52-64 Leonard Street, London EC2A 4JX. Tel: 020 7608 5050 www.bwf.org.uk

The voice of the UK woodworking and joinery industry.

Trada Technology LtdStocking Lane, Hughenden Valley, High Wycombe,Buckinghamshire HP14 4ND Tel: 01494 563091 www.trada.co.uk

Specialists in timber technology information and research.

The Wood Protection Association1 Gleneagles House, Vernongate, Derby DE1 1UP.Tel: 01332 225100www.wood-protection.org info@wood-protection.org

The nationally recognised authority on timber and damp problems.

UK Timber Frame Association LtdHead Office: The e-Centre, Cooperage Way Business Village,Alloa FK10 3LP Tel: 01259 272 140London Office: Clareville House, 26-27 Oxendon Street,London SW1Y 4EL Tel: 020 7235 3364www.timber-frame.org

Promoting timber frame to both the construction industry and the public.

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The Building Research EstablishmentBucknalls Lane, Garston, Watford, Hertfordshire WD2 7JRTel: 01923 664000 www.bre.co.uk

A research-based consultancy, certification and testing business, coveringthe built environment and associated industries.

The Forestry Commision231 Corstorphine Road, Edinburgh EH12 7ATTel: 0131 3340303 www.forestry.gov.uk

The government department responsible for the protection and expansionof Britain’s forests and woodlands.

The Timber Decking AssociationCirce Building, Wheldon Road, Castleford, West Yorkshire WF10 2JT. Tel: 01977 712718 www.tda.org

For advice concerning timber decking, materials and best practice. Seetheir Deckmark Quality Assurance scheme.

The Timber Trade FederationClareville House, 26/27 Oxenden Street, London SW1Y 4EL. Tel: 020 7839 1891 www.ttf.co.uk

For a list of quality timber suppliers throughout the UK, to search for timberproduct supply and for a copy of the TTF Conduct Assurance Scheme.