During the construction of sloped timber roof truss, for protection of timber, which of the following is essential?
- ANo priming and no painting
- BTwo coats of paint over primerCorrect
- COne coat of paint
- DOne coat of primer
Solution
Concept
Timber in roof trusses is protected by a priming coat followed by two coats of paint.
Step-by-step solution
1. Timber can decay from moisture, fungi and insects. 2. A priming coat seals the pores and helps the paint stick. 3. Two coats of paint over the primer give a durable protective layer. 4. So the answer is two coats of paint over primer.
Explanation
Timber members of a roof truss need protection from moisture and decay. Standard practice is one priming coat and then two coats of paint. This gives good sealing and long life.
Why the other options are wrong
A: Without primer or paint, timber is open to moisture and decay. C: One coat of paint without primer sticks poorly and does not protect enough. D: Primer alone is only a base coat and is not a finished protective layer.
Shortcut
Remember the standard rule: 1 primer + 2 paint coats.
Common mistake
Thinking primer alone is enough protection.
Correct answer: B) Two coats of paint over primer