Q.When you go to a timber mart to collect timber for your construction of a new house, how will you select good timber?

Step 1. Check that the timber has been properly seasoned. Freshly cut wood carries significant moisture; timber that has not been seasoned (by air seasoning or the faster, more controlled kiln seasoning) is prone to warping, cracking and shrinking after use, and decays faster. Good timber should be visibly dry and well-seasoned before purchase.

Step 2. Check the proportion of heartwood to sapwood. Heartwood (duramen) is denser, darker and far more resistant to decay and insect attack than sapwood (alburnum), because its vessels are blocked by tyloses and infiltrated with tannins, resins and gums. Timber with a higher proportion of heartwood relative to sapwood will be more durable and longer-lasting for construction use.

Step 3. Check the annual rings. Distinct, evenly spaced, closely packed annual rings generally indicate wood with good density and mechanical strength, since they reflect steady, healthy seasonal cambial activity; irregular or widely spaced rings can indicate weaker wood.

Step 4. Check for physical defects. Good timber should be free of visible defects such as cracks, splits, knots, insect boreholes or signs of fungal decay, all of which weaken the wood's structural integrity. …

List the practical selection criteria - seasoning, heartwood proportion, annual-ring quality and absence of defects - drawn from the cha …

• Focusing only on outward appearance (colour, polish) while ignoring seasoning and heartwood content, which determine actual durability. …