Why is “green” wood used for timber frames?
Timber frames have traditionally been built using green timber – meaning timber that has a high moisture content because it has not been sufficiently air dried or kiln dried. There are several reasons for this tradition: As wood dries it become more difficult to work. Green timber is easier to work with chisels, and other hand tools. Stockpiling timbers until they dry would take two to four years. Most people are not willing to wait years for a timber frame. As green wood dries out it shrinks. We allow for this shrinkage in our design and joinery. As the frame dries, the type of joints we use maintains their tightness. All medieval and new world timber frames used the same type of joints we employ.
Timber also dries and shrinks in cross-section. This results in checking, and will always happen when a timber looses moisture too quickly. The checks do not pose a problem structurally. We help slow the drying process by sealing the end grain of our timbers. We also recommend that the frame not be heated and dried out excessively for one year after it is raised and enclosed. It can be slowed further by not keeping the house too hot and dry during the first year of occupation.