Tree species
Wood is a natural material and is sourced from many different tree species. Each species produces timber which varies in colour, density and performance, all of which will influence its suitability for a particular job.
Softwoods
Softwood timber is obtained from conifers - trees which have needle-like leaves and usually bear cones. They are the most commonly used for timber because they are generally less expensive than hardwoods, are readily available, and easy to work.
Of the 650 species of softwoods throughout the world, approximately 50 are in commercial use.
The main sources of softwood in the UK are Sweden, the British forests of Scotland, England, Wales and Northern Ireland, Finland, Latvia and Russia.
Hardwoods
Hardwoods are mainly broad leaf or deciduous trees, shedding their leaves in winter. There are two groups - temperate and tropical (some tropical hardwoods are evergreen).
There are approximately 20,000 different commercial species. The majority are denser than softwoods due to their cellular structure, but some, particularly tropical hardwoods, grow so fast that they can have a similar or lower density than slow-growing softwoods.
Hardwoods tend to be deeper in colour and are often used decoratively, particularly as veneers on softwood panel products.
Many hardwoods are 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, where there are no significant issues of deforestation or illegal logging.
Tropical hardwoods are sourced from areas such as Central and South America, West and Central Africa and South East Asia. It is essential that any tropical timber you use has credible independent evidence that it is from a legal (and preferably sustainably managed) source. Ask your specialist merchant (see 'Specifying and buying timber')
Table of species and uses
Softwood
Hardwood
Temperate hardwood
Temperate hardwood table - PDF
To view the tables, click on the PDF symbols above. The tables provide an indication of some of the more common softwoods and hardwoods and their uses.
Working qualities refers to ease of working. 'Difficult' indicates that care should be taken in machining to achieve an acceptable surface finish. Health and Safety requirements relating to the use of woodworking tools and machinery and to the control of wood dust should always be followed.
Colour(s) relates to the heartwood of the species. Most timbers vary in colour and will change with use, the application of finishes and exposure to light. Unprotected timber exposed to the weather will discolour and may develop mould growth.
Durability 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
Density varies depending on species and moisture content. Averages at 15% moisture content are quoted; 0.5% of the given weight can be added for every 1% increase in moisture content. ‘*’ indicates that density can vary by 20% or more.
Texture refers to the surface and is classified as fine, medium or coarse.
Treatability 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, and Extremely Difficult.
Moisture movement refers to any change in the dimensions of dried timber in response to atmospheric conditions. Movement is classed as small, medium or large. 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.
Further information and advice
Available species. Information on softwood and hardwood species is usually available from your local timber supplier. Please ask him for advice if required. You may need to contact a specialist merchant for advice on certain hardwood species.
UK grown species. UK Forestry Commission. www.forestry.gov.uk
American hardwoods. The American Hardwood Export Council. www.ahec-europe.org
Procuring sustainable timber. CPET (The government’s Central Point of Expertise on Timber) www.proforest.net/cpet
Visit www.askTRADA.co.uk for additional technical advice and a comprehensive guide to Timber Species.
