Many of those in need of housing have access to small-diameter trees in nearby forests. These trees can be used to produce materials that are ideal for building affordable homes. If used in conjunction with energy-efficient straw bale construction and other natural materials, small-diameter wood can be used to create a better home than most building systems, at lower cost.
US forests have been poorly managed and are now choked with small-diameter trees. Thinning these trees to reduce the risk of forest fires, which is currently at a record high, is a Forest Service priority. With an inexpensive firewood permit, anyone can obtain small-diameter wood for building a home. (Even though this wood could be used for firewood, it is more valuable as a building material.)
There are several advantages to using small-diameter wood for building:
– Small-diameter wood can provide all of the lumber for a house including studs, joists, plates, trusses, window and door frames, trim, and other components. Wood frame construction is the preferred building system in the US because of its speed and ease of construction, but unfortunately most dimensional lumber is not sustainably harvested. Using small-diameter wood encompasses the advantages of wood frame construction but uses wood that improves the health of the forest and reduces forest fires.
– The use of locally available wood reduces construction costs and avoids supporting environmentally irresponsible lumber companies.
– Wood in the round is much stronger than standard dimension lumber and requires less processing. Thus small diameter logs can be used, with fewer parts. For example only one-half as many trusses may be required, because pole trusses can be set every 48 inches (122 centimeters) instead of every 24 inches (61 centimeters).
– A US$40 chainsaw guide can be used to mill purlins, joists, studs, plates, and other components. (The Beam Machine is one example of a low-cost chainsaw attachment that can mill straight edges on poles.)
– The fire resistance of poles is much higher than stick-framed trusses or engineered trusses (TJIs). Wood poles have a two-hour commercial fire rating, in contrast to the other two options, which have a one-hour fire rating. And in the event of a fire, there is no toxic off-gassing – the leading killer in home fires.
– Timber frame/pole construction is more esthetically pleasing than wood frame construction covered with plasterboard. The beauty of the wood is left exposed, honoring the tree from which it came.
– Very few tools are required to build simple pole trusses. If they are built in uniform sizes, workers can be trained to build them quickly.
The use of small-diameter wood creates local jobs and places less reliance on highly processed materials that must be shipped long distances. Jobs are created in four categories:
1. Logging: Workers are needed to cut, mill and deliver poles.
2. Truss manufacturing: Workers are needed to build roof trusses. This could be a cooperative effort or an entrepreneurial cottage industry. Either way the quality will be higher and more consistent if specially trained workers build the trusses.
3. Milling: Workers are needed to mill logs into purlins, studs, plates, or joists. The simplest method uses a chainsaw and a guide. Mass production methods with commercial-sized equipment are even faster and more efficient.
4. Construction: Workers are needed to erect trusses, build walls, etc.
With all the advantages of small-diameter wood, we should take a closer look at how to use this resource that is so often near at hand.
Excerpt by Owen Geiger from Building Without Borders: Sustainable Construction for the Global Village, Joseph F. Kennedy (editor)