What Is Wood?
Timber is one of the most environmentally friendly materials available. It is renewable, biodegradable, non-toxic, energy efficient and greenhouse gas friendly. All other major construction materials are finite. One day they may run out. Trees can be cut down and replanted. Timber can be recycled and when it reaches the end of its life it can be disposed of with minimal impact to the environment because of its non-toxic nature. Timber is one of the best insulation materials. It is 5 times better as an insulator than concrete, 400 times better than steel and 1,770 times better than aluminium. That makes it an excellent material for use in construction to reduce energy bills for both households and business. Timber is extremely versatile, beautiful and is one of the oldest and most natural construction materials known to man. Weight for weight, wood has probably the best engineering properties of any material. Many of its structural properties result from the microscopic layout of its cells and cell walls. Wood is an extremely versatile structural material, ingeniously arranged to provide a living structure that combines both strength and flexibility. With exceptions that prove the rule, trees are usually divided into two broad groupings:
Hardwoods are mainly broadleaved and deciduous trees. They belong to the "flowering" plant group or angiosperms. Most are deciduous with their soft flat leaves falling in autumn. On a world scale, there are two main groupings of hardwoods:-
- a) temperate ones come generally from Europe, North America, southern S. America and New Zealand.
- b) tropical ones are from Central South America, Africa, India, South-East Asia and Australasia.
Softwoods are mainly conifers. They belong to the group of trees called gymnosperms - plants with "naked seeds", normally with cones, and often with needle-like leaves retained all winter. Natural softwoods are found principally in a broad belt stretching across North America, Scandinavia, Russia and Siberia - the Northern Hemisphere temperate zone. The structural properties of hard and softwood differ, a reflection on their life strategies - and these mean they have different uses for Man. Both hardwoods and softwoods come in a range of colours and grain patterns. Hardwoods can range from almost pure white through red to deep brown or even black. Softwoods are paler in colour, ranging from white to yellow, sometimes tinged with colour - although there are exceptions such as red cedar. The colour of both hard and softwoods darkens when exposed to the light. Our page on How Trees Grow provides greater background. More: See our chapter on Tree Biology "Trees: their Natural History" (2000) by P. Thomas published by Cambridge University Press "Trees" (2001) by R. Ennos published by The Natural History Museum, London. The Forestry Commission Scotland has unveiled (2005) its new system for the visual grading of UK-grown hardwoods. Download a copy of 'Making the grade' from www.forestry.gov.uk/hardwoods (2.5MB).