Wood MSE 220 Spring, 2009

Strength of wood increases as it dries. A board in the green condition weighs 11.2 lbs, and in the dry condition weighs 9.8 lbs. Find: (a) the moisture content (b) the shrinkage in % Solution Moisture content = weight of water in wood/dry weight = (11.2 lb. – 9.8 lb.)/9.8 lb. = 14.3% Shrinkage:Volume shrinkage = 1.6% per 4% decrease in moisture Therefore, Volume Shrinkage = 1.6%/4% * 14.3% = 5.7%

Decay & Destruction Four factors that lead to degradation: –Fungi –Bacteria –Insects –Marine organisms Four ways to prevent degradation: –Reduce moisture –Chemical treatment –Use heartwood from decay resistant species –Painting or prohibiting insect entry