Expansion Joint Spacing Calculator

How It Works

Control joints in concrete slabs should be spaced at 2-3 times the slab thickness in feet (e.g., 8-12 feet for a 4-inch slab). For CMU walls, place control joints every 20-25 feet and at openings, corners, and height changes. Brick walls need expansion joints every 20-25 feet since brick expands over time (opposite of concrete which shrinks). Concrete control joints should be cut 1/4 of the slab depth within 6-12 hours of finishing. Always use backer rod and flexible sealant in masonry joints.