An expansion joint is a deliberate gap built into a building material or assembly, filled with flexible sealant, specifically designed to accommodate the expansion and contraction that materials naturally experience with temperature changes without allowing that movement to crack or damage the surrounding material.
Different materials expand and contract at different rates, and even a single material like concrete or stucco needs planned relief points to accommodate its own thermal and moisture-related movement across a large continuous surface.
Without adequate expansion joints placed at appropriate intervals, rigid materials like stucco or concrete are prone to random, uncontrolled cracking as they attempt to accommodate movement without any planned relief point to absorb it.
What Does an Expansion Joint Involve?
- A deliberate gap in the material or assembly
- Backer rod and flexible sealant filling the joint
- Placement at intervals appropriate to the material and expected movement
- Coordination with the overall design to remain visually unobtrusive
Why Are Expansion Joints Important?
By providing planned, controlled locations for materials to expand and contract, expansion joints prevent the random, unsightly cracking that would otherwise occur as rigid materials attempt to accommodate thermal and moisture-related movement without any designed relief point available. This proactive planning approach produces a far better long-term outcome than allowing materials to crack wherever internal stress happens to concentrate.
Expansion joint spacing and placement requirements vary by material and application, with manufacturers and industry standards providing specific guidance that installers should follow rather than guessing at appropriate intervals based on general assumption alone. Following these established guidelines rather than guessing at placement produces more reliable long-term results.
Expansion Joint vs. Control Joint
An expansion joint accommodates general thermal and moisture-related movement across a material. A control joint specifically manages where concrete or similar materials will crack during curing shrinkage, directing that inevitable cracking to a planned, less visible location.