Natural timber is wood cut from a tree into planks of different sizes and cross-sections. There are two types of natural timber. We classify them as hardwoods and softwoods. These names do not refer to the properties of the wood necessarily, as some softwoods can be relatively hard and some hardwoods can possess the mechanical properties of softwoods.

Another way timber can be classified is by the type of trees they come from. Coniferous trees or ‘evergreen’ trees as they are sometimes called are fast-growing trees with needle-like leaves that do not lose their leaves in the winter. Deciduous trees are slower-growing trees with mainly broad, thin leaves that shed during Autumn. Coniferous are generally softwoods, whereas deciduous are hardwoods.

Timber is seasoned (dried) as part of its preparation for commercial use. This process reduces the moisture content so it becomes workable, and avoids cracking and splitting. The remaining moisture, albeit small, means that the wood never really stabilizes and continues to swell and shrink with humidity, temperature and seasonal changes. Further timber-preserving treatment can help with stabilising the wood and prolonging its life.

Timber treatments are an additive preservative to improve the timber's resistance to attack from wood-destroying fungi and insects and improve its durability. Most wood preservers (e.g. stains) soak or penetrate into the wood fibres, rather than sit on the surface. This is often done under pressure in a pressure tank. Treatment is particularly important for applications outside or in sand or soil. Fire retardants help the wood to quickly char when exposed to flames, reducing the smoke and flame that occurs in a fire.

Timber finishes are applied to the surface of the timber to improve the material's natural beauty, but also to protect it from the environment, impact, heat, or moisture. Varnish provides a hard and very tough surface. They increase the surface hardness by sealing the timber completely, protecting the wood fibres from moisture and insect attack. Finishing oils are often made from linseed or mineral oils that protect from moisture and provide a low-sheen finish. Wood wax provides a dull gloss shine and is often made from beeswax. It should be repeatedly applied to wood of good quality furniture to lift the colours of the grain and pleasing finish.

Timber is one of the most renewable materials available which makes the principle and practical aspect of recovery and recycling quite straightforward. Recycling timber was popularised during the 1990s as part of the deforestation and climate change movement. This prompted both timber suppliers and consumers to turn to a more sustainable source. Recycling timber is the environmentally friendliest form of timber production and is very common in countries like the UK, Australia and New Zealand, where supplies of old wooden structures are plentiful. 

Timber can be chipped down and used or repurposed for a large variety of applications. The traditional ‘feedstock’ for the panel board industry still accounts for the majority of recycled wood. Other uses include animal bedding, equestrian or landscape surfaces, play areas, filter beds, pulp for the paper industry and Biomass power plants (e.g. wood pellets).

Biomass is an important fuel in many countries, especially for cooking and heating in developing countries. The use of energy made by biomass plants for transportation and for electricity generation is increasing in many developed countries as a means of avoiding carbon dioxide emissions from fossil fuel use. In 2019, biomass provided about 5% of total primary energy use in the United States.