Concrete
Expansion Joint
A full separation between two concrete sections, filled with compressible material, that allows independent movement due to temperature changes and settlement.
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In the Field
Expansion joints separate the building structure from exterior flatwork, columns, and walls. If concrete can't move freely, it will crack somewhere else. Fill with closed-cell backer rod and sealant — not concrete or grout.
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Rule of Thumb
Expansion joints are typically required every 50–100 feet in exterior flatwork and wherever concrete meets a fixed structure like a column or building wall.