Due to the attack of dry rot, what happens to timber used in construction or carpentry?

Introduction / Context:
This question comes from basic civil engineering and building materials knowledge. Timber is widely used in doors, windows, furniture, roofs, and other structural elements. Understanding how biological attacks such as dry rot affect timber is important for safe design and maintenance. Exam questions often ask about different types of decay like dry rot and wet rot and their visible effects on wood, because these concepts are fundamental to construction practice.

Given Data / Assumptions:
- The question mentions dry rot, which is a particular type of fungal attack on seasoned timber.
- It asks what happens to timber when dry rot occurs.
- The options describe different possible effects, including reduction to powder, cracking, minor weight loss, and shrinking without major damage.
- We assume standard textbook definitions of dry rot as used in civil engineering and building construction courses.

Concept / Approach:
Dry rot is caused by certain fungi that attack seasoned timber in conditions of dampness and poor ventilation. The fungus breaks down the cellulose and binding materials in wood, leading to loss of strength and characteristic powdery residue. The most widely cited effect in civil engineering textbooks is that timber affected by dry rot ultimately reduces to a dry, brown powder and becomes structurally useless. Therefore, the approach is to match this known description with the given options.

Step-by-Step Solution:
Step 1: Recall that dry rot is a type of decay that attacks timber already in use, especially in poorly ventilated, damp locations. Step 2: Know that the fungus responsible for dry rot feeds on the wood, destroying the binding material and leaving behind a brittle mass. Step 3: The typical description of timber affected by dry rot is that it becomes weak, powdery, and can easily be crushed to dust. Step 4: Compare this with the options. The phrase reduces to powder in option A exactly matches this standard description. Step 5: Therefore, the correct effect of dry rot on timber is that it reduces to powder.

Verification / Alternative check:
Civil engineering reference books on building construction usually define dry rot as a disease in timber where, due to fungal action, the wood becomes light, dry, and readily crumbles into powder. They highlight that, unlike mere cracking or shrinking, the structural strength is almost completely lost. Since these sources consistently emphasise the reduction of timber to a powdery state, this confirms that option A is correct.

Why Other Options Are Wrong:
Cracks only: While timber under various stresses can crack, dry rot is more severe than simple cracking. It leads to a powdery mass rather than just cracks, so option B does not capture the core effect.
Loses some weight only: Dry rot does cause loss of mass, but describing it only as slight weight loss understates the severe and destructive nature of the decay, so option C is incorrect.
Shrinks without other damage: Timber drying may cause some shrinkage under normal conditions, but dry rot involves much more than simple shrinkage. It involves degradation of the internal structure and conversion to powder, so option D is wrong.

Common Pitfalls:
One common mistake is to confuse dry rot with general shrinkage or surface cracking, leading candidates to choose options about cracking or shrinkage. Another is to mix up dry rot and wet rot, thinking they have the same effect. To avoid these errors, it is useful to remember a simple link: dry rot results in dry powder, while wet rot usually leaves timber soft, spongy, and damp. Associating the names with their effects helps secure this concept in memory.

Final Answer:
Due to the attack of dry rot, timber eventually reduces to powder and loses its structural strength.