What is the purpose of adding expansion joints at regular intervals in long walls?

• A. To improve insulation
• B. To allow movement and prevent cracks
• C. To increase load capacity
• D. To ease finishing

Answer: (B)

Long walls experience changes in size as temperatures rise and fall and as moisture content shifts, and different sections may move differently due to settlement. Expansion joints provide a designed gap that can open, close, or slide without transferring those stresses from one part of the wall to another. This relief prevents cracking, buckling, and other damage that would occur if the wall tried to stay unbroken under movement. Without joints, continuous walls are prone to cracks where tensile or shear stresses concentrate, especially in long spans. The joints are then filled with a flexible material to accommodate movement and keep water out, which is why the purpose is to allow movement and prevent cracks. The other options don’t address the main issue: insulation, load capacity, or finishing ease aren’t the primary function of expansion joints.