Question

There are two main natural forces responsible for causing defects in timber: abnormal growth and ____________________

(a) rupture of tissues

(b) insects

(c) frost

(d) rain

This question was addressed to me during an interview for a job.

The origin of the question is Classification of Timber, Carpenter’s Work topic in section Rules and Methods of Measurement of Civil Engineering Drawing

Answer 1

The correct answer is (a) rupture of tissues

The explanation is: Rupture of tissue includes cracks or splits in the wood called “shakes”. “Ring shake”, “wind shake”, or “ring failure” is when the wood grain separates around the growth rings either while standing or during felling. Shakes may reduce the strength of a timber and the appearance thus reduce lumber grade and may capture moisture, promoting decay. Eastern hemlock is known for having ring shake. A “check” is a crack on the surface of the wood caused by the outside of a timber shrinking as it seasons.