Building with Trees

Timber is an important material in any build, whether it be for a sustainably built timber framed house, or used for stud walls in our typical brick, modern houses.  It is usually purchased at the timber merchants as a relatively cheap, expendable building material, but what we must remember is that it is part of a tree, and where the tree came from and how it arrived here, plays a big part in the massive energy use accountable to the UK construction industry.

Trees ‘lock up’ carbon dioxide, and by building with trees, rather than burn them or let them decay in their environment, that carbon remains locked in rather than released back into the atmosphere.   However, enormous amounts of timber are imported into the UK, and the further the timber is shipped, the more embodied energy it acquires.  The use of fuel to ship timber half way around the world, and the subsequent carbon released into the atmosphere, can often outweigh the environmental benefits of building with timber. 

Sustainable Forests

It would be great to source all our timber locally, but for the volume of timber required in the industry it’s not practical. What is possible though, is for us to use the right sort of timber for the right situation, and to be aware where that timber has come from.   General lumber which is ideal for stud work comes mostly from Scandinavia.  The wood is grown relatively quickly and so can be harvested like a crop and re-planted.  For all general building, plywood, flooring, door and windows, you can make sure that the timber comes from sustainably managed forests.  Always check that the timber you buy is Forest Stewardship Council (FSC) certified, which guarantees that the timber is from a sustainably managed forest, including overseas forests.  The FSC website is www.fscus.org which will give you more information.

English Timber

Aside from general building, the timber framing industry is growing for this good structural timber is required, with most companies offering frames in green oak.  In the UK we don’t have enough stock of native English oak, so most of it is imported from France, but should we be using oak for timber framing?  Apart from farmed oak in France, oak is a scarce resource which should be limited to good furniture or display pieces within buildings where it can be appreciated.

Fortunately, we have another source of this timber.  Approximately 60 years ago in the UK, the forestry commission planted thousands of hectares of douglas fir and western red cedar trees.  They were intended to be harvested for mining pit props, and so had to be structurally strong. As they are relatively fast growing, we have mature plantations ready for harvest, which are currently being used mostly for wood pulp and chip. Douglas fir only takes about 60 years to mature, compared to a couple of hundred years for an oak tree.

Douglas fir is perfect for timber framing as it is as structurally strong as oak. In the right circumstances, douglas fir can be used green, where as most timber is kiln dried quickly, or air dried for a couple of years.  Western red cedar has a natural preservative in it and so is perfect for cladding. For external uses, timber without natural preservatives has to be tanalised.  This process pressure impregnates the wood with toxic chemicals including arsenic.  Why buy imported tanalised timber when untreated UK grown timber can be used for the same purpose?

Douglas fir and western red cedar can be easily and environmentally purchased.  Either by buying locally felled trees and having them cut yourself on site by a mobile sawmill, a service which is readily available locally from Black Dog Sawmills, or by going to a local sawmill such as Bulbarrow Timber who fell the timber locally and will cut it to your specification.

The felling of trees such as douglas fir in the UK is mostly done whereby the forest is managed, not cleared.  Selective felling in this way means that our woods and forests won’t disappear. In fact, if more people bought their timber in this way, the woodland would be more profitable and better looked after.  Landowners would have more incentive to keep and manage the woodland, and in turn this could help regenerate rural communities by creating local jobs.

Our Impact Upon the Rainforests

Unfortunately, the majority of the industry is not set up to use UK timber, but to import it.  As builders or consumers, it is our responsibility to make sure we know that the imported timber we use has come from a sustainably managed forest by looking for the FSC logo, or by using locally sourced hard woods where appropriate.   What we should not be encouraging is the use of tropical hardwoods both in building or for our furniture. Topical forests are being illegally cleared at a  frightening rate, and as the ‘lungs of the planet’  this is predicted to massively impact on future climate change. Instead we should be using English, or at least European hardwoods, and at the same time reducing the carbon polluting effects of importing.  Continued demand for tropical hardwoods such as mahogany means that tropical forests and rain forests will continue to the cleared.  By purchasing English hardwoods at the local sawmill we really can ‘do our bit’ and eliminate that demand.

By Rob Buckley
Dorset Centre for Rural Skills

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