The nominal thickness of an expansion joint in brick walls, is kept more than A. 5 mm B. 10 mm C. 15 mm D. 20 mm

The correct answer is: C. 15 mm.

An expansion joint is a structural separation between two parts of a building or other structure that allows for movement without damage. The nominal thickness of an expansion joint in brick walls is kept at 15 mm to allow for the expansion and contraction of the

Option A: 5 mm is too small a thickness for an expansion joint in brick walls. This would not allow for enough movement, and could result in damage to the brickwork.

Option B: 10 mm is a more reasonable thickness for an expansion joint in brick walls. However, it is still possible that this would not be enough movement, and could result in damage to the brickwork in certain circumstances.

Option C: 15 mm is the recommended thickness for an expansion joint in brick walls. This allows for enough movement to prevent damage to the brickwork, while also being a practical and cost-effective solution.

Option D: 20 mm is too thick for an expansion joint in brick walls. This would not be necessary, and would add unnecessary cost and complexity to the project.