Construction joint
A construction joint is a planned interface between two successive concrete pours. Reinforcement must continue through it unless the engineer details otherwise.
Ask Chalkline about this →A construction joint is a planned interface between two separate concrete pours, used when placing the entire volume of concrete in one continuous operation is not practical. Common in slabs poured in bays, walls poured in lifts, and any site where the pour is interrupted and the concrete has partially or fully set before the adjacent section is placed.
The key requirement is continuity: reinforcement must pass through the joint unless the structural design explicitly details a movement joint or a dowelled joint at that location. Cutting reo at a construction joint without engineer approval creates a structural discontinuity.
At the joint face, the hardened concrete must be prepared to ensure bond: this typically means roughening the surface to expose aggregate (mechanical scabbling, sandblasting, or retarder applied before initial set), cleaning off laitance, and ensuring the old face is sound and damp before the fresh concrete is placed against it. A construction joint differs from a cold joint: a cold joint is an accidental, unplanned pour stoppage that leaves a weak interface; a construction joint is planned and detailed.
Also known as: pour joint, day joint.
Category: Concrete / Joints.
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Last updated: 2026-05-08. Verified: 2026-05-08. Quarterly review for currency.