Rebar Placement Basics for Slabs

Correct placement is as important as selecting the bar size. Poor placement can make reinforcement ineffective.

Key placement principles

• Support steel: use chairs so the mat stays where intended during the pour.
• Maintain cover: keep steel away from soil and edges to reduce corrosion risk (local requirements vary).
• Lap splices: follow appropriate lap lengths for your bar size and specification.
• Keep it continuous: avoid gaps at door openings and re-entrant corners unless detailed.

Common mistakes

• Steel ends up on the bottom because it was not chaired.
• Bars are too close to edges and rust/spall occurs.
• Joints cut through reinforcement without load transfer detailing.