Expansion joints in masonry walls primarily serve to prevent which problem?

• A. Water leakage
• B. Cracking in walls
• C. Color fading of the finish
• D. Dust infiltration

Answer: (B)

Expansion joints are placed to let masonry sections move independently as temperatures, moisture, settlement, or other forces cause expansion and contraction. Masonry walls are strong in compression but not in tension, so when a large wall is forced to expand or contract and the sections are tied together, stresses build up and cracks form in bricks and mortar. The flexible gap provided by an expansion joint lets adjacent wall bays slide a little relative to each other, or open and close slightly, without transferring those stressful forces across the joint. That movement accommodation is what prevents cracks from developing. Water leakage can be a secondary concern if joints aren’t sealed well, but the main purpose is to stop cracking by allowing controlled movement.