wood as a building material
DESCRIPTION
Description of wood as a building material, how to treat it and the various uses of its different typesTRANSCRIPT
WOOD
Different woods are the palette of the furnituremaker. They provide color and texture, strength and beauty to handmade furniture.
Each type of wood has characteristics to be considered when building a piece of furniture. Some are very hard and durable; some are flexible and suitable for bending. "Hardwood" is a term applied to trees that lose their leaves in winter. "Softwood" describes evergreens such as fir, pine and redwood. The actual durability a wood is described in a range from very soft to very hard.
Every wood has a distinctive grain structure. Woods such as white and red oak, ash and walnut have "open-pores". These woods have small holes in their surface that give the piece a textural quality. When a stain is applied to this type of surface, the stain tends to collect in the "open-pores" and appears darker than the rest of the piece. Tight grained woods include maple, alder, and cherry. These woods are smooth to the touch and can take finish evenly.
The color and grain look of different types of wood
California Softwoods and HardwoodsAlder, Pacific Maple, Black Oak, Madrone, Tan Oak, Redwood, Myrtlewood(pepperwood), Claro Walnut, Western Red Cedar, and Yew
Humboldt County woodworkers prize the unique woods of the Pacific Northwest for their beauty and durability. Local woodworkers use native woods alone and in combination with domestic and exotic species creating the furniture that is part of the distinctive designs of Northern California.
AlderWarm brown color with a figure like cherry. Alder is a medium soft wood suitable for cabinetry and furniture with the appropriate sized joinery.
Pacific MapleGolden yellow wood with a variety of figure available, can be found in the curly or fiddleback varieties. This is a medium hard wood suitable for all types of furniture.
MadroneOne of the harder California native woods, Madrone has a reddish pink color with streaks of color throughout. Madrone is used in furniture and turnings, and can be used in flooring and architectural woodwork.
Softwoods and HardwoodsAsh, Basswood, Beech, Birch, Butternut, Tennessee Aromatic Cedar, Cherry, Fir, Hickory, Maple, Pine, Poplar, Red Oak, Walnut, White Oak.Long a staple of the American furnituremaker, these mostly eastern hardwoods are most familiar to the public. Humboldt County woodworkers use these woods to make the finest handmade furniture.
MapleHard rock maple is one of the hardest of domestic woods. The "select white" grade of maple has a warm gold-ivory color when finished with a hand rubbed oil. Because of its hardness rock maple is suitable for all types of furniture and cabinetry.
CherryFurniture grade cherry is a moderately heavy, hard, strong, wood. Close grained, it can be polished to a deep and glowing red. Many of the finest early American table tops and interior panels were made of cherrywood. This wood is suitable for all furniture and cabinetry including chairs.
WalnutNorth American walnut is one of the most prized hardwoods. It can range in color from deep rich brown to an almost purple brown. This is an open-pored wood that is relatively hard. Walnut is durable and finishes beautifully. The wood is useful in many furniture applications.
Exotic WoodsAndiroba, Bayo, Bloodwood, Bocote, Bubinga, Spanish Cedar, Chaktekok, Chechen, Chicozapote, Cocobolo, Ebony, Fishtail Oak, Granadillo, Ironbark, Ipe, Jabin, Jarrah, Jatoba, Katalox, Kingwood, Koa, Lacewood, Lignum Vitae, African Mahogany, Machiche, Narra, Obeche, Pau Ferro, African Paduak, Peruvian Walnut, Purpleheart, Brazilian Rosewood, Satinwood, Snakewood, Teak, Vesi Wenge, Zebrawood
With bright colors and expressive grain patterns these woods are often used as highlights in furnishing and turnings. Also, some of these exotic woods such as African mahogany and granadillo are excellent for building whole pieces of furniture, chairs and cabinetry.
LacewoodA relatively soft wood grown widely in Australia, lacewood has an unusual grain structure that has the look of hammered copper when properly cut. It can be used as an accent wood or in veneered tabletops.
GranadilloA beautiful, very hard wood from Southern Mexico with a tan-deep brown streaking. This close grained wood is a "Smart Wood" selectively harvested in cooperation with the indigenous people. This wood is suitable for all furniture applications.
African MahoganyHere is traditional mahogany, deep rich, red and suitable for any furniture application. This wood is imported from Ghana, which has had a sustained yield forestry program in place since 1910.
Common nameBinomial nomenclatureColourDensityLocationCharacteristics, Usage and Status
Aini or AangiliArtocarpus hirsutusYellowish brown595 kg/mMaharashtra,Andhra Pradesh,Tamil Nadu,Karnataka,KeralaElastic, close-grained, and strong. It takespolish. It can be usedunderwater. It is used for ordinary building construction, structural work,paving,furnitureand so forth.
ArjunTerminalia arjunaTerminalia ellipticaDark brown870 kg/mCentral IndiaIt is heavy and strong. It has such uses asbeams,rafters, and posts.
AxlewoodAnogeissus latifolia930 kg/mAndhra Pradesh, Tamil Nadu, Maharashtra,Madhya Pradesh,Bihar,Uttar PradeshIt is very strong, hard and tough. It takes a smooth finish. It is subject to cracking.
BabulAcacia niloticasubsp.indicaWhitish red835 kg/mRajasthan, Andhra Pradesh, Maharashtra, Madhya Pradesh, Tamil Nadu, Karnataka,Bengal,Gujarat, Uttar PradeshIt is strong, hard and tough and it takes up a good polish. It is used for such products as bodies andwheelsofbullock cart, agricultural instruments, tool handles, and well curbs.
BakulMimusops elengiMimusops parvifolia[2]Reddish brown880 kg/mSome parts of North IndiaIt is close-grained and tough. It is used for makingcabinets.
BambooFamilyPoaceae, tribe BambuseaeThroughout India, especiallyAssamand BengalNot actually a tree, but a woody grass, it is flexible, very strong and durable. It is used forscaffoldings, thatched roofs, rafters, temporary bridges, and so forth.
BanyanFicus benghalensisBrown580 kg/mThroughout IndiaIt is strong and durable only under water. The aerial roots are utilized for such items as tent poles and well curbs.
BenteakLagerstoemia parviflora675 kg/mKerala, Madras, Maharashtra, KarnatakaIt is strong and takes up a smooth surface. It may be used for building constructions,boat buildingand furniture.
BijasalPterocarpus marsupiumLight brown800 kg/mKarnataka, Andhra Pradesh, Madhya Pradesh, Maharashtra, Kerala, Uttar Pradesh, Tamil Nadu,OrissaIt is coarse-grained, durable and strong but difficult to work. Termites (also known as white ant) do not easily attack it. It is used for ordinary building construction and forcartwheels.Vulnerable
CasuarinaCasuarinaspp.Reddish brown765 kg/mAndhra Pradesh, Tamil NaduIt grows straight. It is strong and fibrous. It is, however, badly twisted. It is often used for scaffolding and posts for temporary structures.
CoconutCocos nuciferaReddish brownThroughout coastal IndiaTakes polish. Requires preservative treatment. Used as poles, piles, furniture and as formwork in concrete construction.
DeodarCedrus deodaraYellowish brown560 kg/mHimalayas,Punjab, Uttar PradeshDeodar is the most important timber tree providing soft wood. It can be easily worked and it is moderately strong. It possesses distinct annual rings. It is used for making cheap furniture, railway carriages, railway sleepers, packing boxes, structural work and so forth.
GumarGymnema sylvestrePale yellow580 kg/mCentral India,South IndiaIt can be easily worked and is strong and durable especially when used under water. It is used for such products as furniture, carriage, well curbs,yokes, and door panels.
HopeaHopea parvifloraLight to deep brown1010 kg/mMadras, KeralaHopea is extremely strong and tough. It is difficult to work. However, it can be seasoned easily and it is durable and not likely to be damaged by white ants. It has been variously used for ordinary house construction, railway sleepers,piles, and boat building.Endangered
Himalayan Elm, Indian ElmUlmus wallichianaRed960 kg/mThroughout IndiaIt is moderately hard and strong. It is used for door and window frames, carts, and so forth.
Ironwood, Penaga Lilin,Bosneak, Gangaw, MesuaMesua ferreaReddish brown960-1060 kg/mIronwood is durable though it is very hard and is not easily worked. It even resists penetration of nails. It is used for ordinary house construction, bridges, piles, agricultural instruments, railway wagons, and railway sleepers.
Irul, PyinkadoXylia xylocarpa830-1060 kg/mKarnataka, Kerala, Andhra Pradesh, Maharashtra, Orissa, Tamil NaduIt is very hard, heavy and durable. Difficult to work, it also requires slow and careful seasoning. It is used for railway sleepers, agricultural instruments, paving blocks, and heavy construction.Least concern
JackMangifera caesia.Yellow, darkens with age595 kg/mKarnataka, Maharashtra, Tamil Nadu, KeralaIt is compact and even grained. It is moderately strong and easy to work. It takes a good finish and maintains its shape well. It has many uses including plain furniture, boat construction, well curbs, door panels, cabinet making and musical instruments.
JarulLagerstroemiaflos-reginaeLight reddish gray640 kg/mAssam, Bengal, MaharashtraHard and durable, it can be easily worked. It takes a good finish and is used for house construction, boat building, railway carriages, cart making and scaffolding.
Kathal, Keledang, JackfruitArtocarpus heterophyllusYellow to deep brown800 kg/mKarnataka, Andhra Pradesh, Kerala, Maharashtra, Tamil NaduIt is heavy and hard. It is durable under water and in damp conditions, however, it cracks if exposed to direct sun. White ants do not attack it. It is used for piles, platforms of wooden bridges, door and window panels.
Lauraceae, SajLauraceaeDark brown880 kg/mKarnataka, Andhra Pradesh, Bihar, Orissa, Madhya Pradesh, Kerala, Tamil NaduIt is strong, hard and tough. It is subject to cracking and attack by dry rot. White ants do not attack it. It takes a smooth finish. It is used for such purposes as house construction, boat construction, railway sleepers and structural work.
MahoganySwieteniaspp.Reddish brown720 kg/mIt takes a good polish and is easily worked. It is durable under water. It is most commonly used for furniture, pattern making and cabinet work.
MangoMangiferaspp.Deep gray560-720 kg/mThroughout IndiaThe mango tree is well known for its fruits. It is easy to work and it maintains its shape well. It is moderately strong. It is most often used for cheap furniture, toys, packing boxes, cabinet work, panels for doors and for windows.
MulberryMorusspp.Brown650 kg/mPunjabIt is strong, tough and elastic. It takes up a clean finish. It can be well seasoned. It is turned and carved easily. Mulberry is typically used for baskets and sports goods likehockey sticks,tennis racketsandcricket bats.
OakQuercusspp.Yellowish brown865 kg/mOak is strong and durable, with straight silvery grain. It is used for preparing sporting goods.
PalmArecaceaeDark brown1040 kg/mThroughout IndiaIt contains ripe wood in the outer crust. The colour of this ripened wood is dark brown. It is strong, durable and fibrous. Palm is used for furniture, roof covering, rafters and joists.
PinePinusspp.Pine wood is hard and tough except white pine which is soft. It decays easily if it comes into contact with soil. It is heavy and coarse grained. It is used for pattern making, frames for doors and windows, and for paving material. White pine is light and straight grained and is used in the manufacture ofmatches.
Red cedarRed480 kg/mAssam, NagpurIt is soft and even grained. It is used for furniture, door panels and well curbs.
RosewoodDalbergia latifoliaDark850 kg/mKerala, Karnataka, Maharashtra, Madhya Pradesh, Tamil Nadu, OrrissaIt is strong, tough and close-grained. It is a handsome wood that takes up a high polish. It maintains its shape well and is available in large sizes. It is used for furniture of superior quality, cabinet work, ornamental carvings and so forth.Vulnerable
SalShorea robustaBrown880-1050 kg/mKarnataka, Andhra Pradesh, Maharashtra, Uttar Pradesh, Bihar, Madhya Pradesh, OrissaIt is hard, fibrous and close-grained. It does not take up a good polish. It requires slow and careful seasoning. It is durable under ground and water. It is used for railway sleepers,shipbuilding, and bridges.
SandalwoodSantalumspp.White or Red930 kg/mKarnataka, Tamil Nadu, Kerala, Assam, Nagpur, BengalIt has a pleasant smell. It is commonly used for agricultural instruments, well curbs, wheels, and mallets.Vulnerable
SatinwoodChloroxylon swieteniaYellow960 kg/mCentral and Southern IndiaIt is very hard and durable. It is close grained. It is used for furniture and other ornamental works.Vulnerable
SimulBombaxspp.White450 kg/mAll over IndiaIt is a loose grained, inferior quality wood. Light in weight, it is used for packing cases, the match industry, well curbs, and for cheap furniture.
SirisAlbiziaspp.Dark brownNorth IndiaHard and durable, Siris wood is difficult to work. It is used for well curbs in salty water, beams, posts, and furniture.
SissooDalbergia sissooDark brown770 kg/mMysore, Maharashtra, Assam, Bengal, Uttar Pradesh, OrissaAlso known asshishamortali, this wood is strong and tough. It is durable and handsome and it maintains its shape well. It can be easily seasoned. It is difficult to work but it takes a fine polish. It is used for high quality furniture,plywoods, bridge piles, sport goods, railway sleepers and so forth. It is a very good material for decorative works andcarvings.
SprucePiceaspp.480 kg/mSpruce wood resists decay and is not affected by the attack of marine borers. It is however liable to shrink, twist and warp. It is used for piles under water and (formerly) for aeroplane construction.
SundriHeritiera fomesDark red960 kg/mBengalIt is hard and tough. It is difficult to season and work. It is elastic and close grained. It is strong and durable. These qualities make it suited for such uses as boat building, piles, poles, tool handles, and carriage shafts.
TamarindTamarindus indicaDark brown1280 kg/mAll over IndiaTamarind is knotty and durable. It is a beautiful tree for avenue and gardens. Its development is very slow but it ultimately forms a massive appearance. Its fruit is also very useful. It is used for agricultural instruments, well curbs, sugar mills, carts and brick burning.
TeakTectona grandisDeep yellow to dark brown639 kg/mCentral India and Southern IndiaModerately hard, teak is durable and fire-resistant. It can be easily seasoned and worked. It takes up a good polish and is not attacked by white ants and dry rot. It does not corrode iron fastenings and it shrinks little. It is among the most valuable timber trees of the world and its use is limited to superior work only.
Toon, Red CedarToona ciliataReddish brown or dull red450 kg/mAssamIt can be easily worked. It is light in weight. It is used for such products as furniture, packing boxes, cabinet making and door panels.
WOOD-ALL OVER THE WORLDSpecies/Timber type/DensityTextureMoistureWorkingDurabilityTreatabilityAvailability/RemarksUses
OriginColourkg/m3movementqualitiesFungiHeartwoodPrice
AburaHardwoodMedium/ModeratelyLimitedColour variable. Resistant toInterior joinery,
Hallea ciliata580*SmallMediumNot durable
Light brownfineeasyLowacidsmouldings
W Africa
AfrormosiaHardwoodMedium/Durable - veryExtremelyDarkens on exposure. Stains inInterior and exterior
Pericopsis elata710SmallMediumCITES IIcontact with iron in dampjoinery. Furniture.
Light brownfinedurableDifficult
W AfricaconditionsCladding
Afzelia (doussi)HardwoodMedium/Medium/ExtremelyLimitedExudes yellow dye in dampInterior and exterior
Afzelia spp830*SmallVery durable
Reddish-browncoarsedifficultdifficultMediumconditionsjoinery. Cladding
W Africa
AgbaModerately
GossweilerodendronHardwoodLimitedGum exudation may beInterior and exterior
510MediumSmallGooddurable -Difficult
balsamiferumYellowish-brownMediumtroublesomejoinery, trim. Cladding
durable
W Africa
AndirobaHardwoodMedium/Slightly durableLimited
Carapa guianensis640SmallMedium- moderatelyDifficultInterior joinery
Pink to red-browncoarseMedium
S Americadurable
Ash, AmericanHardwoodRegularInterior joinery, trim.
Fraxinus spp670*CoarseMediumMediumNot durableEasy
Grey, brownMediumTool handles
USA
Ash, EuropeanHardwoodMedium/ModeratelyRegularSelected stock may be toughInterior joinery. Sports
Fraxinus excelsior710*MediumGoodNot durable
White to light browncoarseeasyMediumand suitable for bendinggoods
Europe
Aspen (American,Hardwood
Canadian)ExtremelyVariable
Grey, white to pale450FineLargeMediumNot durableInterior joinery. Matches
Populus tremuloidesdifficult **Low
brown
Canada, USA
BalsaHardwoodLimitedHigh buoyancy value. GoodHeat, sound and
Ochroma lagopus160*FineSmallGoodNot durableDifficult
WhiteMediuminsulating valuevibration insulation
S America
Balau (yellow)HardwoodExtremelyVariableA hard, heavy, strong timber.Heavy structural work,
Shorea sppYellow-brown to980*MediumMediumMediumDurablebridge and wharf
difficultLowObtainable in large sizes
S E Asiared-brownconstruction
BasswoodHardwoodLimitedConstructional veneer.
Tilia americanaCreamy white to420FineMediumGoodNot durableEasyTurnery, piano keys,
Medium
N Americapale brownwoodware
Beech, EuropeanHardwoodEasyFurniture, interior
Whitish to pale(red heartRegular
Fagus sylvatica720FineLargeGoodNot durableExcellent bending propertiesjoinery, flooring.
brown, pinkish-red ifextremelyLow/Medium
Europesteameddifficult)Plywood
Species/Timber type/DensityTextureMoistureWorkingDurabilityTreatabilityAvailability/Remarks
OriginColourkg/m3movementqualitiesFungiHeartwoodPrice
Birch, AmericanHardwoodEasy -RegularIncludes yellow birch andFurniture. Plywood.
Betula sppLight to dark reddish640/710FineLargeGoodNot durablemoderately
Lowpaper birchFlooring
North Americabrowneasy
Birch, EuropeanHardwoodEasy -LimitedIncludes silver birch and whitePlywood. Furniture.
Betula pendula, B. pubescens670FineLargeGoodNot durablemoderately
White to light brownLowbirchTurnery
Europeeasy
Cedar of LebanonSoftwoodMedium/LimitedJoinery. Garden
Cedrus libani580MediumGoodDurableDifficultPungent cedar odour
Light brownsmall **Lowfurniture. Gates
Europe
Cedar, Central/SHardwoodCabinet work, interior
AmericanExtremelyLimited
Pinkish-brown to480CoarseSmallGoodDurableDistinctive odourjoinery. Racing boat
Cedrela sppdifficultMedium
dark reddish-brownbuilding. Cigar boxes
Central & S America
Cherry, AmericanHardwoodModeratelyLimitedCabinet making,
Prunus serotinaReddish-brown to580FineMediumGoodNo information
durableMediumfurniture, interior joinery
USAred
Cherry, EuropeanHardwoodModeratelyLimitedInclined to warp; use in smallCabinet making,
Prunus avium630FineMediumGoodNo information
PInkish-browndurableMedium/Highsectionsfurniture
Europe
Chestnut, horseHardwoodLimitedBrush backs. Fruit trays
Aesculus hippocastanumWhite to pale510FineSmallMediumNot durableEasy
Lowand boxes
Europeyellow-brown
Chestnut, sweetHardwoodExtremelyLimitedStains in contact with iron inInterior and exterior
Castanea sativa560MediumLargeGoodDurable
Yellowish-browndifficultMediumdamp conditionsjoinery. Fencing
Europe
DantaHardwoodModeratelyDifficult -LimitedFlooring. Joinery.
Nesogordonia papaverifera750FineMediumGoodextremely
Reddish-browndurableLowTurnery
W Africadifficult
Douglas firModeratelyMarked flame-like growth ringPlywood. Interior and
Pseudotsuga menziesiiSoftwood530MediumSmallGooddurable -ExtremelyRegularfigure. Long lengths and clearexterior joinery.
N America & UKLight reddish-browndifficultMediumConstruction. Vats &
durablegrades available
tanks
EbonyHardwood1030/ExtremelyLimitedGenerally small sizes onlyUsed primarily for
Diospyros sppBlack, someFineMediumMediumVery durabledecorative work.
1190difficultHighavailable. Dust may be irritant
W Africa, India, Sri Lankagrey/black stripesTurnery, inlaying
Ekki/azobHardwoodDurableExtremelyLimitedModerately resistant to termiteHeavy construction;
Lophira alataDark red to dark1070CoarseLargeDifficultattack. Acid resistant.marine and freshwater.
(variable)difficultLow/Medium
W AfricabrownObtainable in large sizesBridges, sleepers, etc
Elm, EuropeanHardwoodModeratelyLimitedIncludes smooth leaved elm,Furniture, coffins. Boat
Ulmus spp560*CoarseMediumMediumSlightly durable
EuropeLight browneasy - DifficultMediumwych elmbuilding
Species/Timber type/DensityTextureMoistureWorkingDurabilityTreatabilityAvailability/RemarksUses
OriginColourkg/m3movementqualitiesFungiHeartwoodPrice
Elm, WhiteHardwoodLimitedGood strength, toughness andFurniture. Coffins.
Ulmus americana580CoarseMediumMediumSlightly durableDifficult
Pale reddish-brownMediumbending propertiesRubbing strips
N America
GaboonHardwoodLimitedUsed principally for
Aucoumea klaineana430MediumMediumMediumSlightly durableDifficult
Pinkish brownMediumplywood and blockboard
W Africa
Gedu nohor/edinamHardwoodModeratelyExtremelyLimitedFurniture, interior and
Entandrophragma angolense560MediumSmallMedium
Reddish browndurabledifficultLow/Mediumexterior joinery
W Africa
GeronggangHardwoodVariable
Cratoxylon arborescens540CoarseMediumMediumSlightly durableEasyInterior joinery
Pink to redLow
S E Asia
GreeenheartHardwoodExtremelyVariableHeavy construction;
Ocotea rodiaeiYellow/olive green to1040FineMediumDifficultVery durableAvailable in very large sizesmarine and freshwater.
difficultMedium
Guyanabrownbridges, etc
GuareaHardwoodDurableExtremelyVariableFine dust may be irritant.Furniture, interior
Guarea cedrata590MediumSmallMedium
Pinkish brown(variable)difficultLow/MediumResin exudation may occurjoinery, cabinet making
W Africa
Hemlock, WesternSoftwoodModeratelyRegularObtainable in large sizes, long
Tsuga heterophylla500FineSmallGoodSlightly durableConstruction. Joinery
N AmericaPale browneasy - DifficultLow/Mediumlengths and clear grades
Hevea - see Rubberwood
HickoryHardwoodModeratelyLimitedGood steam bendingStriking tool handles.
Carya sppBrown to830CoarseLargeDifficultSlightly durableproperties. Good shockLadder rungs. Sports
easyMedium
N America (Eastern)reddish-brownresistancegoods
IdigboModeratelyStains yellow in contact with
Terminalia ivorensisHardwoodExtremelyVariablewater; stains in contact withInterior and exterior
560*MediumSmallMediumdurable /
W AfricaYellowdifficultMediumiron when wet. Acidic and mayjoinery. Plywood
Durable
corrode ferrous metals.
IrokoHardwoodMedium/Durable /ExtremelyRegularOccasional deposits of stoneExterior and interior
Milicia excelsa, M. regia660MediumSmalljoinery. Bench tops.
Yellow-browndifficultVery durabledifficultLow/Mediummay occur
W AfricaConstructional work
JarrahHardwoodExtremelyLimitedHeavy constructional
Eucalyptus marginata820*MediumMediumDifficultVery durable
Pink to dark reddifficultLow/mediumwork. Flooring
Australia
JelutongHardwoodRegularPattern making. Drawing
Dyera costulata470FineSmallGoodSlightly durableEasyLatex ducts may be present
White to yellowMediumboards
S E Asia
KapurHardwoodDurable / VeryExtremelyVariableExterior joinery.
Dryobalanops spp770*MediumMediumMediumCamphor-like odourDecking. constructional
Reddish-browndurabledifficultMedium
S E Asiause
Species/Timber type/DensityTextureMoistureWorkingDurabilityTreatabilityAvailability/RemarksUses
OriginColourkg/m3movementqualitiesFungiHeartwoodPrice
KarriHardwoodExtremelyLimited
Eucalyptus diversicolor900MediumLargeDifficultDurableHeavy construction
Reddish-browndifficultMedium
Australia
KempasHardwoodLimitedSlightly acidic and may
Koompassia malaccensisOrange-red to880CoarseMediumDifficultDurableDifficultencourage corrosion of ferrousHeavy constructional use
Low
S E Asiared-brownmetals
Keruing, apitong, gurjun,HardwoodModeratelyHeavy and general
yangPinkish-brown to740*MediumLarge/DifficultdurableDifficultRegularLiable to resin exudationconstruction. Decking,
Dipterocarpus sppMedium(variable)Low
dark brown(variable))vehicle flooring
S E Asia
Larch, EuropeanSoftwoodSlightly durableExtremelyRegularBoat planking.
Larix deciduaPale reddish-brown550FineSmallMedium/ ModeratelydifficultLowTransmission poles
Europedurable
Larch, JapaneseSoftwoodSlightly durableExtremelyRegularStakes. General
Larix kaempferiReddish-brown530FineSmallMedium/ ModeratelydifficultMediumconstruction
Europedurable
Lauan - see Meranti
Lignum vitaeHardwoodExtremelyCITES IIBushes and bearings.
Guaiacum spp1250FineMediumDifficultVery durableObtainable in small sizes only
Dark green/browndifficultHighSports goods
Central America
Limba/afaraHardwoodModeratelyLimitedFurniture. Interior
Terminalia superbaPale yellow,560*MediumSmallGoodSlightly durable
W Africabrown/straweasyLow/mediumjoinery
Lime, EuropeanHardwoodLimited/Carving, turnery. Bungs.
Tilia sppYellowish-white to560FineMediumGoodNot durableEasy
LowClogs
Europepale brown
Mahogany, AfricanHardwoodModeratelyExtremelyRegularFurniture, cabinet work.
Khaya spp530*MediumSmallMedium
Reddish-browndurabledifficultLow/MediumBoat building. Joinery
W Africa
Mahogany, AmericanHardwoodExtremelyCITES IIIFurniture, cabinet work.
Swietenia macrophylla560*MediumSmallGoodDurableRegularInterior and exterior
Reddish-browndifficult
Central & S AmericaHighjoinery. Boat building
MakorHardwoodFurniture. Interior and
Tieghemella heckelii,ExtremelyVariable
Pinkish-brown to640FineSmallMediumVery durableFine dust may be irritantexterior joinery. Boat
T. africanadifficultMedium
dark redbuilding. Plywood
W Africa
Maple, rockHardwoodRegularExcellent flooring timber.
Acer saccharum, A. nigrum740FineMediumMediumSlightly durableDifficultHigh resistance to abrasion
Creamy whiteMediumFurniture. Sports goods
N America
Species/Timber type/DensityTextureMoistureWorkingDurabilityTreatabilityAvailability/RemarksUses
OriginColourkg/m3movementqualitiesFungiHeartwoodPrice
Maple, soft
Acer saccharinum,Hardwood550*FineMediumMediumSlightly durableModeratelyLimitedFurniture. Interior
A. rubrumCreamy whiteeasyMediumjoinery. Turnery
N America
MengkulangHardwoodLimitedInterior joinery.
Heritiera spp720CoarseSmallMediumSlightly durableDifficult
Red, brownMediumConstruction. Plywood
S E Asia
Meranti, dark red/darkHardwoodSlightly durableExtremely
red seraya/red lauanRegularInterior and exterior
Medium to dark710*MediumSmallMedium- durabledifficult
Shorea sppLow/Mediumjoinery. Plywood
red-brown(variable)(variable)
S E Asia
Meranti, light red/lightSlightly durableExtremely
red seraya/white lauanHardwoodRegular
550*MediumSmallMedium/ ModeratelydifficultInterior joinery. Plywood
Shorea sppPale pink to mid redLow
durable(variable)
S E Asia
Meranti, yellow/Extremely
yellow serayaHardwoodLimited
660*MediumSmallMediumSlightly durabledifficultInterior joinery. Plywood
Shorea sppYellow-brownLow/Medium
(variable)
S E Asia
MerbauHardwoodDurable / VeryExtremelyVariableLiable to stain in contact withJoinery. Flooring.
Intsia bijuga, I. palembanicaMedium brown to830CoarseSmallModerate
durabledifficultMediumiron in damp conditionsStructural work
S E Asiadark red-brown
NiangonHardwoodModeratelyExtremelyVariableInterior and exterior
Heritiera utilis, H. densiflora640*MediumMediumGood
W AfricaReddish browndurabledifficultLowjoinery. Furniture
NyatohHardwoodSlightly durableExtremelyVariableFurniture. Interior
Palaquium sppPale pink to720*FineMediumMedium/ ModeratelydifficultLowjoinery.
S E Asiared-browndurable
Oak, American redHardwoodModeratelyRegularFurniture. Interior
Quercus sppYellowish-brown790MediumMediumMediumSlightly durable
easy/ DifficultMediumjoinery
N Americawith red tinge
Oak, American whiteHardwoodModeratelyAcidic nature; iron staining mayFurniture, cabinet work.
Quercus sppPale yellow to770MediumMediumMediumdurable /ExtremelyRegularoccur in damp conditions. MayInterior and exterior
N AmericadifficultMediumjoinery. Flooring. Tight
mid-brownDurablealso corrode metals
cooperage
Oak, EuropeanIron staining may occur inFurniture. Interior and
Quercus robur, Q. petraeaHardwoodMedium/Medium/ExtremelyVariableexterior joinery.
720*MediumDurabledamp conditions, similarly
EuropeYellowish-browncoarsedifficultdifficultMedium/HighFlooring. Tight
corrosion of metals
cooperage. Fencing
Species/Timber type/DensityTextureMoistureWorkingDurabilityTreatabilityAvailability/RemarksUses
OriginColourkg/m3movementqualitiesFungiHeartwoodPrice
Oak, JapaneseHardwoodModeratelyExtremelyVery limitedFurniture. Interior
Quercus mongolica (mainly)670MediumMediumMedium
Pale yellowdurabledifficult**Highjoinery
Japan
Oak, Tasmanian
Eucalyptus delegatensisHardwood610/CoarseMediumMediumModeratelyDifficultLimitedFurniture. Interior
E obliqua, E regnansPale pink to brown710*durableMediumjoinery
Australia & Tasmania
Obeche /wawaHardwoodRegularInterior joinery.
Triplochiton scleroxylon390MediumSmallGoodNot durableDifficult
White to pale yellowLow/MediumFurniture. Plywood
W Africa
OpepeHardwoodHeavy construction.
Nauclea diderrichiiModeratelyVariableMarine and freshwater
Yellow to750CoarseSmallMediumVery durable
W AfricaeasyLowuse. Exterior joinery.
orange-yellow
Flooring
PadaukHardwoodInterior and exterior
Pterocarpus spp740*/ModeratelyLimited
Red to darkCoarseSmallMediumVery durableDust may be irritantjoinery. Turnery.
W Africa, Andamans,850easyHigh
purple-brownFlooring
Myanmar
Parana pineSoftwoodNot durable -ModeratelyRegular
Araucaria angustifoliaGolden brown with550FineMediumGoodDistortion may occur in dryingInterior joinery. Plywood
Slightly durableeasyLow/Medium
S Americabright red streaks
Pine, Canadian redSoftwoodModeratelyLimited
Pinus resinosaReddish yellow,450FineSmallGoodSlightly durableConstruction. Joinery
easyLow
N Americawhite
Pine, CorsicanSoftwoodSlightly durableExtremelyRegularJoinery, construction
Pinus nigra var maritimaLight yellowish-510CoarseSmallMedium(variable)difficultLow
Europebrown(variable)
Pine, elliotis
Pinus elliottiiSoftwood590MediumMediumMediumSlightly durableModeratelyRegularPallets, packaging.
Brazil, Chile (PlantationPale brown to yelloweasyLowJoinery
grown)
Pine, JackSoftwoodModeratelyVariable
Pinus banksianaPale brown/ reddish500MediumMediumMediumSlightly durableConstruction, joinery
easyLow
Canada, USAbrown
Pine, lodgepoleSoftwoodSlightly durableDifficult -
Pinus contortaYellow to paleRegular
470FineSmallGood- ModeratelyExtremelyConstruction. Joinery
N Americabrown tinged withLow
durabledifficult
red
Pine, maritimeSoftwoodMedium-Slightly durableRegularPallets and packaging.
Pinus pinaster530MediumGood- ModeratelyDifficult
Pale brown to yellowCoarseLowJoinery
Europedurable
Species/Timber type/DensityTextureMoistureWorkingDurabilityTreatabilityAvailability/RemarksUses
OriginColourkg/m3movementqualitiesFungiHeartwoodPrice
Pine, patulaSoftwoodModeratelyLimitedPallets and packaging.
Pinus patula590MediumMediumMediumSlightly durable
Pale brown to yelloweasyLowJoinery
South Africa
Pine, pitch, AmericanSoftwoodSlightly durableDifficult -RegularDenser material also known asInterior and exterior
Pinus palustris, P. elliottiiYellow-brown to670*MediumMediumMedium- ModeratelyExtremelylongleaf yellow pine or longleafjoinery. Heavy
Medium
Southern USAred-browndurabledifficultpitch pineconstruction
Pine, ponderosaSoftwoodModeratelyVariable
Pinus ponderosaPale to dark yellow480FineSmallGoodSlightly durableConstruction. Joinery
easyLow
N Americato reddish-brown
Pine, radiataSoftwood
Pinus radiataNot durable -ModeratelyRegularConstruction, furniture,
Yellow to pale480MediumMediumGood
S Africa, S America,Slightly durableeasy - DifficultLowpackaging
brown
Australia, New Zealand
Pine, ScotsSoftwoodSlightly durableDifficult -Regular
Pinus sylvestrisPale yellowish-510CoarseMediumMedium- ModeratelyExtremelyConstruction, joinery
Low
UKbrown to red-browndurabledifficult
Pine, SouthernSlightly
Pinus spp including P.SoftwoodDifficult -
durable/RegularAlso know as Southern yellowConstruction, joinery.
palustris, P. elliottii, P.Pale yellow to light590MediumMediumMediumExtremely
ModeratelyLowpinePlywood
echinata, P. taedabrowndifficult
durable
Southern USA
Pine, yellowSoftwoodModeratelyRegularAlso known as Quebec yellowPattern making, drawing
Pinus strobusPale yellow to light420FineSmallGoodSlightly durable
easyLow/mediumpine and Eastern white pineboards, doors
N Americabrown
Plane, EuropeanHardwoodNoLimitedQuarter sawn materialDecorative purposes.
Platanus x hispanica640FineMediumNot durableNo information
Mottled browninformationMediumproduces lacewood figureInlay work
Europe
PoplarHardwoodFine/DifficultVariablePallet blocks, box
Populus sppGrey white to pale450LargeMediumNot durableboards, turnery. Wood
Medium(variable)Low
Europebrownwool
Poplar, American yellowsee Tulipwood
PurpleheartHardwoodMedium/ModeratelyExtremelyLimitedHeavy construction.
Peltogyne sppPurple to880MediumSmalldurable -
DifficultdifficultHighFlooring. Turnery
Central & S Americapurplish-brownDurable
RaminHardwoodVariable
Gonystylus spp670MediumLargeMediumNot durableEasyMouldings. Furniture
White to pale yellowLow/Medium
S E Asia
Redwood, EuropeanSoftwoodSlightly durableDifficult -Regular
Pinus sylvestrisPale yellowish-510MediumMediumMedium- ModeratelyExtremely
Low
Scandinavia/USSRbrown to red browndurabledifficult
Construction. Joinery.Furniture
Species/Timber type/DensityTextureMoistureWorkingDurabilityTreatabilityAvailability/RemarksUses
OriginColourkg/m3movementqualitiesFungiHeartwoodPrice
RosewoodHardwoodUnlikely to be available as raw
Dalbergia sppMedium to darkExtremelyD nigraInterior joinery. Cabinet
870*MediumSmallMediumVery durablematerial. Fine dust may be
S America, Indiapurplish-brown withdifficultCITES Iwork, turnery
irritant
black streaks
Rubberwood / heveaHardwoodMedium/Medium -Medium/
Hevea brasiliensisCream to light560Not durableEasyLimitedFurniture, Turnery
CoarseLargeGood
Brazil, S E Asiabrown
SapeleHardwood
EntandrophragmaMedium reddish-640MediumMediumMediumModeratelyDifficultRegularInterior joinery.
cylindricumbrown with markeddurableMediumFurniture. Flooring
West Africastripe figure
SepetirHardwoodExtremelyLimited
Sindora spp680MediumSmallDifficultDurableJoinery. Furniture
Golden browndifficultLow
S E Asia
Seraya- see Meranti
SesendokHardwoodMediumLimitedMouldings, interior
Endospermum sppPale cream to straw480SmallMediumNot durableEasyAlso known as Kauvula (Fiji)
to coarseLow/mediumjoinery
S E Asiayellow
Spruce, CanadianSoftwood400*/Not durable -Regular
Picea sppMediumSmallGoodDifficultConstruction.
White to pale yellow500Slightly durableLow
Canada
Spruce, SitkaSoftwoodNot durable -RegularConstruction. Packaging,
Picea sitchensis450CoarseSmallGoodDifficult
Pinkish-brownSlightly durableLowpallets
North America, UK
SycamoreHardwoodLimited
Acer pseudoplatanusWhite or630FineMediumGoodNot durableEasyTurnery. Joinery
Medium
Europeyellowish-white
TaunHardwoodModeratelyDifficult -LimitedStructural work.
Pometia pinnata720CoarseMediumMediumExtremelyTurnery, joinery,
Pale pinkish-browndurableLow
S E Asiadifficultfurniture
TeakHardwoodFine dust may be irritant. Good
Tectona grandischemical resistance. ResistantFurniture. Interior and
Golden brown,ExtremelyRegular
Burma, Thailand660MediumSmallMediumVery durableto termites. Some cultivatedexterior joinery. Boat
sometimes with darkdifficultHigh
and plantations elsewheremarkingstimber may have lowerbuilding
durability
Tulipwood /Poplar,Hardwood
American yellowYellowish to olive510FineMediumGoodSlightly durableNo informationLimitedJoinery, Furniture
Liriodendron tulipiferabrown with darkMedium
N Americastains
Species/Timber type/DensityTextureMoistureWorkingDurabilityTreatabilityAvailability/RemarksUses
OriginColourkg/m3movementqualitiesFungiHeartwoodPrice
UtileHardwoodModeratelyExtremelyRegularInterior and exterior
Entandrophragma utile660MediumMediumMediumdurable -joinery. Furniture and
Reddish-browndifficultMedium
W AfricaDurablecabinet work
Virola, lightEasy -
Virola sppHardwoodLimitedCarpentry, mouldings.
530*MediumMediumMediumNot durableModerately
Dialyanthera sppPale pinkish-brownLowFurniture. Plywood.
easy
Central and S America
WallabaTransmission poles.
Eperua falcata,HardwoodExtremelyLimited
910CoarseMedium**MediumVery durableGum exudation likelyFlooring, Decking. Heavy
E. grandifloraDull reddish-browndifficultMedium
construction
Guyana
Walnut, AfricanHardwoodSlightly durableDifficult -
Lovoa trichilioidesYellowish-brown,VariableFurniture, cabinet work.
560MediumSmallMedium- ModeratelyExtremely
W Africasometimes with darkMediumand exterior joinery
streaksdurabledifficult
Walnut, AmericanHardwoodSmall/ModeratelyDifficult -Variable
Juglans nigra660CoarseGoodExtremelyAlso known as Black walnutFurniture. Gun stocks
Rich dark brownMedium**durableMedium/High
N Americadifficult
Walnut, EuropeanHardwoodModeratelyLimitedStaining likely if in contact withFurniture, turnery. Gun
Juglans regiaGrey-brown with670CoarseMediumGoodDifficult
durableHighiron under damp conditionsstocks
Europedark streaks
Weng / Panga pangaHardwoodInterior and exterior
Millettia laurentiiExtremelyLimited
Dark brown with880*CoarseSmallGoodDurablejoinery. Flooring.
M stuhlmanniidifficultMedium
fine black veiningTurnery
Central & E Africa
Western red cedarFine dust may be irritant. An
Thuja plicataSoftwoodModeratelyDifficult -Regularacidic timber which mayShingles, exterior
N America390CoarseSmallGooddurable -Extremelycorrode metals under dampcladding. Greenhouses,
Reddish-brownMedium
Durabledifficultconditions and cause ironbeehives
staining
Whitewood, American - see Tulipwood
Whitewood, EuropeanSoftwoodDifficult -RegularJoinery. Construction.
Picea abies and Abies albaWhite to pale470MediumMediumGoodSlightly durableExtremely
LowFlooring
Europe, USSRyellowish browndifficult
WillowHardwoodLimitedCricket bats. Boxes,
Salix spp450FineSmallGoodNot durableDifficult
pinkish-whiteMedium/highcrates
Europe
YewSoftwoodSmall/Very LimitedFurniture, turnery.
Taxus baccataOrange-brown to670MediumDifficultDurableDifficult
Medium**HighInterior joinery
Europepurple-brown
CUTTING
A mountain ash (Eucalyptus regnans) being felled. Dated to c. 1884-1917, Australia
TimberjackHarvesterat workLoggingis the cutting, skidding, on-site processing, and loading oftreesorlogsontotrucks[1]orskeleton cars.Inforestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually asawmillor alumber yard. However, in common usage, the term may be used to indicate a range of forestry or silviculture activities.Illegal loggingrefers to what in forestry might be called timber theft.It can also refer to the harvest, transportation, purchase or sale of timber in violation of laws. The harvesting procedure itself may be illegal, including using corrupt means to gain access to forests; extraction without permission or from a protected area; the cutting of protected species; or the extraction of timber in excess of agreed limits. In common usage what is sometimes called clearcut logging is not is necessarily considered a type of logging but a harvest or silviculture method and is simply calledclearcuttingor block cutting. In the forest products industry logging companies may be referred to as logging contractors.Cutting trees with the highest value and leaving those with lower value, often diseased or malformed trees, is referred to as high grading. It is sometimes called selective logging, and confused with selection cutting, the practice of managing stands by harvesting a proportion of trees. Logging usually refers to above-ground forestry logging. Submerged forests exist on land that has been flooded by damming to createreservoirs. Such trees are logged usingunderwater loggingor by the lowering of the reservoirs in question.Ootsa LakeandWilliston LakeinBritish Columbia,Canada, are notable examples where timber recovery has been needed to remove inundated forests. ClearcuttingClearcutting, or clearfelling, is a harvest method that removes essentially all the standing trees in a selected area. Depending on management objectives, a clearcut may or may not have reserve trees left to attain goals other than regeneration,[7]including wildlife habitat management, mitigation of potential erosion or water quality concerns.Silvicultureobjectives for clearcutting, (for example, healthy regeneration of new trees on the site) and a focus onforestrydistinguish it fromdeforestation. Other methods include Shelterwood cutting, group selective, single selective, seed-tree cutting, patch cut and retention cutting.Logging methods
TheWashington Iron Works Skidderin Nuniong is the only one of its kind in Australia, with donkey engine, spars and cables still rigged for work.The above operations can be carried out by different methods, of which the following three are considered industrial methods:Tree-length loggingTrees are felled and thendelimbedand topped at the stump. The log is then transported to the landing, where it isbuckedand loaded on a truck. This leaves theslash(and the nutrients it contains) in the cut area where it must be further treated if wildland fires are of concern.Full-tree loggingTrees and plants are felled and transported to the roadside with top and limbs intact. The trees are then delimbed, topped, and bucked at the landing. This method requires that slash be treated at the landing. In areas with access to cogeneration facilities, the slash can bechippedand used for the production of clean electricity or heat. Full-tree harvesting also refers to utilization of the entire tree including branches and tops. This technique removes both nutrients and soil cover from the site and so can be harmful to the long term health of the area if no further action is taken, however, depending on the species, many of the limbs are often broken off in handling so the end result may not be as different from tree-length logging as it might seem.
Cut-to-length loggingCut-to-length loggingis the process of felling, delimbing, bucking and sorting (pulpwood, sawlog, etc.) at the stump area, leaving limbs and tops in the forest.Harvestersfell the tree, delimb and buck it, and place the resulting logs in bunks to be brought to the landing by askidderorforwarder. This method is routinely available for trees up to 900 mm in diameter. Harvesters are employed effectively in level to moderately steep terrain. Harvesters are highly computerized to optimize cutting lengt, control harvest area byGPSand utilize price list for each specific logs to archive most economical results during harvesting.SpringboardsThe image at the top of the page illustrates the use of springboards. Loggers cut aspringboard notchinto which they insert the springboard, which is then used as a platform, allowing the logger to stand above obstructions/snow or to cut higher-up where the trunk is narrower.Transporting logs
Timber raftinginJoensuucanalat 2009.Felled logs are then generally transported to a sawmill to be cut intotimber, a paper mill forpaper pulp, or for other purposes like fence posts. There were many methods for moving logs from where they were cut to a rail line of a mill. The cheapest methods of transportation of timber arelog drivingandtimber raftingwhich makes use of a river's current to move floating tree trunks downstream tosawmillsandpaper mills. To help herd the logs to the mill, in 1960 the Alaskan Lumber and Pulp Mill had a specially designed boat that was constructed of 1 1/2 inch steel. In the late 1800s and the first half of the 1900s the most common method was thehigh-wheel loaderwhich was a set of wheels over ten feet tall that the log or logs were strapped beneath. Oxes were first used with thehigh-wheel loaders, but in the 1930s tractors replaces the oxes.In 1960 the largest high wheel loader was built for service in California. Called theBunnyan Buggiethe unit was self propelled and had wheels 24 feet high and a front dozer blade that was 30 feet across and 6 feet high.Log transportation can be challenging and costly since trees are often far from navigable roads.Road buildingand maintenance may be restricted inNational Forestsor other wilderness areas since it can cause erosion inriparian zones. When felled logs sit adjacent to a road, heavy machinery may simply lift logs onto trucks. Most often, special heavy equipment is used to gather the logs from site and move them close to the road to be lifted on trucks.Many methods exist to transport felled logs lying away from roads.Cable logginginvolves ayarderwhich pulls one or several logs along the ground to platform where a truck is waiting. When the terrain is too uneven to pull logs on the ground, askylinecan lift logs off the ground vertically, similar to aski lift.Heli-logging, which uses heavy-lift helicopters to remove cut trees from forests by lifting them on cables attached to a helicopter, may be used when cable logging is not allowed due to environmental concerns or when roads are lacking. It reduces the level of infrastructure required to log in a specific location, reducing the environmental impact of logging.Less mainstream forms of log transport, or methods used previously include horses, oxen, or balloon logging.
SEASONINGSeasoning is the controlled process of reducing the moisture content (MC) of the timber so that it is suitable for the environment and intended use. We need to reduce the MC of timber for the following reasons:_ Every time the MC reduces the timber shrinks especially tangentially._ Consequently it will show fewer tendencies to warp, split or shake._ Seasoned timber although lighter will be stronger and more reliable.The sap in timber is a food for fungi and wood parasites. Remove the sap and the wood will be less attractive to these dangers. For construction grade timber the timber must be below 20% MC to reduce the chances of Dry Rot and other fungi infestations._ Dry well seasoned timber is stronger._ Dry well seasoned timber is easier to work with and consequently safer especially machine working.Timber with higher moisture content is difficult to finish i.e. paint, varnish, etc.There are two main ways of seasoning timber, Natural (Air) and Artificial (Kiln) drying. Both methods require the timber be stacked and separated to allow the full circulation flow of air, etc. around the stack.
Air Seasoning.Air seasoning is the method used with the timber stacked in the open air. It requires the following:Stacked stable and safely with horizontal spacing of at least 25 mm.Vertical spacing achieved by using timber battens (piling sticks) of the same or neutral species.Today some timber yards are using plastics.The piling sticks should be vertically aligned and spaced close enough to prevent bowing say 600 to 1200 mm max centres. Ends of boards sealed by using a suitable sealer or cover to prevent too rapid drying out via the end grain.The stack raised well clear of the ground, vegetation, etc to provide good air circulation and free from rising damp, frost, etc.Over head cover from effects of direct sunlight and driving weather.The details depend on the size, quantity and species of the timber.You cannot however expect to obtain less than 16 - 17% mc in the UK.Further seasoning needs to be done inside, in heated and ventilated buildings.
Kiln Seasoning.
There are two main methods used in artificial seasoning, compartmental, and progressive.Both methods rely on the controlled environment to dry out the timber andrequire the following factors:_ Forced air circulation by using large fans, blowers, etc._ Heat of some form provided by piped steam._ Humidity control provided by steam jets.The amount and duration of air, heat and humidity again depends on species, size, quantity, etc. Schedules are published for the various species to enable operators to select an appropriate drying environment.In the UK they are usually provided by the Kiln Manufacturers and also published in the Handbook of Hardwoods and Handbook of Softwoods (BRE).
Compartmental.
A compartment kiln is a single enclosed container or building, etc. The timber is stacked as described above and the whole stack is seasoned using a programme of settings until the whole stack is reduced to the MC required. Compartment kilns differ from progressive kilns in that the timber is loaded into the kiln and remains in place throughout the drying process. Compartment kilns are usually smaller than progressive kilns, and because of their construction the temperature and humidity conditions within them can be closely controlled.Consequently, they are often used to dry expensive material or woods which are difficult to dry. Circulation may be either forced or natural just as with progressive kilns. Drying conditions cannot be controlled as closely in natural draft compartment kilns, however, as in forced draft kilns, and the rate of drying is also slower. For these reasons kilns built today are of the forced draft type and many of the old natural draft types have been converted.
Progressive.
In the progressive kiln, timber enters at one end and moves progressively through the kiln much as a car moves through a tunnel. Temperature and humidity differentials are maintained throughout the length of the kiln so that the lumber charge is progressively dried as it moves from one end to the other. Progressive kilns may be further subdivided into naturaldraft kilnsin which heated air is allowed to rise through the material by natural convection, andforced draft kilnsin which fans are employed to force the air through the wood. A progressive kiln has the stack on trolleys that progressively travel through chambers that change the conditions as it travels through the varying atmospheres.
Progressive Kiln
The advantage of this system, although much larger, has a continuous flow of seasoned timber coming off line.A number of commercial processes for seasoning of timber are available, the most common of which is kiln-drying. Kiln seasoning accelerates the process of seasoning by using external energy to drive the moisture out. The timber is stacked in much the same way as it is for air drying, and is placed inside a chamber in which the conditions can be varied to give best seasoning results. Air is circulated around the charge (stacked timber) and the temperature and humidity can be varied to give optimum drying. Each species has different cell characteristics and therefore requires different drying schedules. Typically the timber may be in the kiln for a period of between two days to one week.Generally, it is not feasible to kiln-dry structural timber in thicknesses greater than 45 mm, although there are limited amounts of 70 mm thick kiln-dried softwood members in the market place. All untreated structural pine and some commercial hardwoods are seasoned, mostly using kilns that are often heated by sawmill by-products or gas.Plenty of research is continually being done to determine kiln drying schedules for different species. An optimum schedule will remove the moisture as quickly as possible, with the minimum quantity of introduced energy, and giving minimum damage to the dried timber.After kiln seasoning, there is often some damage to cells near the surface of the wood. (All of the moisture passes through those cells.) They have in fact collapsed, but can easily be pumped back up in a reconditioning chamber. This chamber introduces steam for a period and puts some moisture back into the outer cells and removes the effect of seasoning collapse.Hard woods have closed cell structure, so take more time in being seasoned and dried.