TIMBER SPECIES

Wood Campus Timber Trade Topics are produced in collaboration with the Timber Trade Federation. For further information, visit www.ttf.co.uk

TOPIC CHECKLIST

  • Is the species suitable for the end use?
  • Does it have the right strength qualities?
  • How durable is it?
  • What does it look like?
  • Will it last?
  • Are there legal and sustainable supplies?

What are the main types of timber species?

Softwoods

Softwood timber is obtained from conifers – trees with needle-like leaves, usually bearing cones. Softwoods are the most commonly-used timber because they offer good value and are readily available from sustainably-managed forests. They are less dense and easier to work with than most hardwoods.
Of the 650 species of softwoods throughout the world, around 50 are in commercial use, with the most common being European Redwood and Whitewood (pine and spruce).
Most softwood used in the UK comes from Sweden, the UK, Finland, Latvia, Germany and Russia.

Hardwoods

Hardwoods are mainly broadleaf, deciduous trees, shedding their leaves in winter, although some hardwoods are evergreen. There are two groups, temperate and tropical, accounting for some 20,000 different commercial species.
Although generally more durable and stronger than softwood, they must be used in the correct way and environment.
The majority of hardwoods are deeper in colour and have a higher density than softwood, due to their cellular structure. However, some hardwoods, particularly tropical species, grow fast enough to be of similar, or lower, density than slow growing softwoods.
Hardwoods are usually supplied in random lengths and widths, but in standard thicknesses are often used as veneers on softwood.

Temperate hardwoods

Found in temperate areas of the world, such as Europe, North America, South America, Asia, Australia and New Zealand, most of the temperate hardwoods used in the UK, such as oak, birch or beech, come from Europe or North America.

Tropical hardwoods

Found in tropical areas such as Central and South America, West and Central Africa and South East Asia.
Illegal trade in tropical hardwoods has been largely responsible for deforestation. Care should be taken to ensure you are supplied with timber from legal and sustainable sources.
See Wood Campus CPD module Procuring Sustainable Timber.

Which species of wood should I choose?

Consider these points:
  1. The end use – for example, is the wood to be used as a structural material and then covered with something else, i.e. studding covered by plasterboard, or will it be exposed?
  2. What strength is required? Does the timber need to have a high bending strength, such as a joist, or a high tensile strength where the timber is stretched in the application?
  3. Is the wood to be used purely for a decorative effect? Is this to be a dark or light colour?
  4. Is the wood to be machined? Some species are more easily machined than others.
  5. Is the wood from a certified legal and sustainably-managed forest source (i.e. FSC or PEFC) or is it from a source that is making progress towards certification (i.e. Verified Progress)?
  6. Cost. It may look nice, but is it worth the additional cost, if another less expensive and more commercially available timber can do the same job?
  7. Durability and treatability: is it necessary to use preservatives?
Softwoods - main characteristics
Species/OriginColourDensity kg/m2TextureMoisture movementWorking qualitiesDurability1Treatability2 (heartwood)Uses
Redwood, European Scandinavia/EuropeCreamy white510MediumMediumMediumSlightly to moderately durableDifficult to extremely difficultFlooring, external and interior joinery, furniture, structural
Whitewood, European Scandinavia/EuropeWhite to pale yellowish brown470MediumMediumGoodSlightly durableDifficult to extremely difficultFlooring and interior joinery, furniture, structural
Scots pine UKCreamy white510CoarseMediumMediumSlightly to moderately durableDifficult to extremely difficultExternal and interior joinery, structural
Douglas fir N America, UK and EuropeReddish brown to light brown530MediumSmallGoodModerately durableExtremely difficultInterior and exterior joinery, cladding
Larch, European EuropePale reddish brown550FineSmallMediumSlightly to moderately durableExtremely difficultCladding, trim
Western red cedar N AmericaReddish brown390CoarseSmallGoodModerately durableDifficult to extremely difficultCladding
Spruce, Sitka N America And UKReddish brown450CoarseSmallGoodNot durable to slightly durableDifficultInterior joinery, packing, pallets, structural
Temperate hardwoods - main characteristics
Species/OriginColourDensity kg/m2TextureMoisture movementWorking qualitiesDurability1Treatability2 (heartwood)Uses
Beech, European
Europe, UK
White/cream (reddish brown after steaming)720FineLargeGoodNot durableEasy (red heart extremely difficult)Furniture, interior joinery, flooring, plywood
Birch, European
Europe, Scandinavia
Light brown670FineLargeGoodNot durableEasy to moderately easyCabinet making, furniture, plywood
Cherry, European
Europe, UK, Scandinavia, Asia, N.Africa
Pinkish brown510FineMediumGoodModerately durableNo informationCabinet making furniture
Chestnut, Sweet
Europe, UK, Asia Minor, Australia, N.Africa
Yellow to brown530MediumLargeGoodDurableExtremely difficultInterior and exterior joinery, fencing, trim, structural
Oak, European
Europe, Asia Minor, N.Africa
Yellowish brown550Medium to coarseMediumMedium to difficultDurableExtremely difficultFurniture, interior and exterior joinery, flooring, heavy structural
Tropical hardwoods - main characteristics
Species/OriginColourDensity kg/m2TextureMoisture movementWorking qualitiesDurability2Treatability3 (heartwood)Uses
Teak
Burma, Indonesia, Thailand and plantations elsewhere
Golden brown some with dark markings660MediumSmallMediumVery durableExtremely difficultInterior and exterior joinery, sports goods, furniture
Iroko
W.Africa
Yellow brown660MediumSmallMedium to difficultDurable to very durableExtremely difficultinterior and exterior joinery, bridge construction
Sapele
W.Africa
Reddish brown640MediumMediumMediumModerately durableDifficultInterior and exterior joinery, furniture, flooring, veneer
Utile
W.Africa
Reddish brown660MediumMediumMediumModerately durable to durableExtremely difficultInterior and exterior joinery, furniture, cabinet work

1Moisture movement

For structural purposes movement is not usually significant, but if you require stability in varying humidities (e.g. decorative flooring), use a species with small movement. These classifications are not directly related to the shrinkage of green timber.

2Durability

Refers to resistance to fungal decay of the heartwood only. Sapwood in most species is generally not durable and should not be used in exposed conditions without preservative treatment. Classes referred to in BS EN 350-1 are:

Class 1 – ‘very durable’

Class 2 – ‘durable’

Class 3 – ‘moderately durable’

Class 4 – ‘slightly durable’

Class 5 – ‘not durable’

3Treatability

Refers to how easily timbers can be penetrated with vacuum pressure preservative treatments. The four levels of treatability in BSEN 350-2 are ‘easy’, ‘moderately easy’, ‘difficult’, ‘extremely difficult’.

Modified timber

A number of brands of timber are now available that have been modified chemically, such as Accoya™, or by heat treatment, such as Thermowood.
Generally, these products provide the sustainability of softwoods with the stability and durability normally associated with hardwoods.
The different modification processes affect the performance of the timbers in different ways. Consult the manufacturer for specific details.

Tannin stain

Tannin is natural in softwoods and hardwoods. For example, oak and Western red cedar will exude tannin as they dry, which may give the appearance of a black deposit. As a result, water running off these surfaces can leave staining, particularly around metal fixings.

Further information and advice

Sourcing sustainable timber

Available species

Consult your local timber merchant or Timber Trade Federation member www.ttf.co.uk

Swedish grown species

www.swedishwood.com

UK grown species

www.forestry.gov.uk

American species

americansoftwoods.com

Technical information

www.trada.co.uk

Sustainable timber

Timber is the most sustainable mainstream building product. It is naturally renewable. Over 90% of timber used in UK construction comes from Europe, where more trees are grown than harvested (source: TTF Statistical Review 2016).
Softwood and temperate hardwood forests in Scandinavia, Europe, Canada and North America are stable or growing. Growing forests act as carbon sinks; wood products act as carbon stores.
Ask for PEFC or FSC Chain of Custody certification.
See Wood Campus RIBA CPD module Procuring Sustainable Timber for more on timber certification and sustainability and government requirements.