Wood Durability

When most people hear the word “durability” in relation to wood, they immediately think of its ability to withstand dents and scrapes. However, in this context it specifically refers to a wood’s ability to resist elemental and natural forces of decay. (The former notion of durability equating to physical toughness would be better explored through Janka hardness and Modulus of Rupture values.)

Degradation can occur from fungus (caused by cycles of rain/moisture), or from termites or other boring/destructive insects. An overall chart defining the terms used to describe a wood’s durability in direct ground contact:

Classification Service Life(in years)
Very Durable 25+
Durable 15-25
Moderately Durable 10-15
Non-Durable 5-10
Perishable less than 5

 

This durability assessment is only based on the tree’s heartwood, and not its sapwood—as only the heartwood, due to its extractives, has any appreciable degree of durability; in nearly all instances, sapwood should be considered perishable.

Some genera of Bamboo are only expected to last 6 months to 3 years in direct ground contact. On the other end of the spectrum is wood such as Teak, which is well-known for its durability, and is frequently used in boatbuilding and other outdoor applications.

In addition to the length of time the wood can physically maintain its structural integrity, there’s also the matter of a wood’s weathering characteristics. Weathering can’t be as clearly expressed in a single number or measurement, but overall, woods with good weathering characteristics exhibit limited photo-degradation (caused by UV rays in sunlight), as well as above-average resistance to contraction and expansion, warping, and surface checking due to seasonal changes in temperature and humidity.

Because of this vague definition, only woods that have notably good (or notably poor) weathering characteristics will be noted. (Again, Teak is noted for both its excellent durability and its superb weathering characteristics.)

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Joe Bloggs

A friend is interested in buying an Eric-32 boat (still unfinished) that two brothers spent thirty years building. One bro died and the other bro is now too elderly to continue. Allegedly the wood is Mahogany (no idea what type) Allegedly the best boats were built from an Indian Teak known as Ironwood which is allegedly so hard that the marine worms won’t eat it. How is Mahogany going to compare? The boat has never been put into the water but rainwater that has accumulated inside the hull constantly drips out of joints between the planks. Personally I wouldn’t touch… Read more »

Amani Boudan

How did your friend go with the boat?