Category: Structure & materials
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
An expansion joint is a deliberate gap that divides a long building or a large slab into parts so it can expand and contract with temperature without cracking.
Why it matters on a project
Where day and night temperatures swing widely, missing joints cause long cracks in roofs and walls.
Measurement and pricing
Measured in linear metres including filler and sealant.
Common mistake
Tiling or plastering over the joint without a matching joint in the finish, so the finish cracks along it.
Frequently asked questions
How far apart are expansion joints?
The designer decides based on building length, structure type and climate.
Is an expansion joint the same as a construction joint?
No. A construction joint separates two pours with continuous rebar; an expansion joint cuts the structure to allow movement.
Related terms
- Flexible polyurea sealantA flexible joint filler tolerating movement and chemicals, used in industrial floors.
- WaterproofingLayers preventing water ingress into structural elements or spaces, such as bituminous membranes and cementitious coatings.
- Solid slabA concrete slab of uniform thickness without voids, common for small and medium spans.
- Plaster (render)A cement or gypsum layer applied to walls to level them before paint or cladding.
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