Civil Engineering ► Engineering Materials ► Wood & Timber

Wood & Timber

Wood age

Trees have age, just like humans do. Older trees are more stable but not as strong as middle-aged trees. Younger trees move more and are not ready to use. Tight grain is what we prefer, but the grain can be too tight because it will start to lose strength at some point.

As trees grow in one season, they grow faster from spring through summer and more slowly from fall through winter. That is what we see in tree rings. Tighter grain means less space in fast-growing fibre. This space in looser grain is where the moisture stays, which is why tighter grain is more stable than looser grain. Density is also heavier in tighter grain. The increased density means that the wood is stronger.

British Columbia's forest resources are managed. Forestry management controls when trees are planted and harvested. Trees that come out of these managed forests are about 50 years old, and the size of the butt (bottom) is about 14 inches. This means that the trees contain 50 rings in seven inches, or seven rings per inch. The wood we are sourcing has 8 to 13 rings per inch, so it is around 100 years old or older.

TIMBER DECAY

Deterioration occurs mainly due to

• Decay or rot
• Insects, marine borers
• Fire

Timber not properly seasoned or subjected to intermittent wetting decays ► due to fungi, termites as various portions of the wood are used as food. They require both oxygen and excess moisture ► hence timber having less than 25% moisture or fully submerged in water will not decay or rot. Termites also attack wood. They eat wood and form tunnels or tubes inside. Certain species of beetles and ants will damage timber by digging tunnels through it using the wood for living quarters rather than food. The major disadvantage of timber is the ease with which it burns as compared with structural materials.