Category: Structure & materials
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
Spacers are concrete or plastic blocks of the required cover thickness, tied to or placed under the reinforcement to keep a fixed gap between steel and formwork or ground. Top steel in slabs sits on chairs.
Why it matters on a project
Without them steel touches the formwork, shows after striking, or ends up with thin cover that rusts within years.
Common mistake
Using broken bricks or stones under the steel instead of spacers; they crack or absorb water and become weak points.
Frequently asked questions
Plastic or concrete spacers?
Concrete suits elements against soil and moisture; plastic is common in slabs and internal walls.
How far apart should spacers be?
Per bar size and specification; the point is that the steel does not sag between them.
Related terms
- Concrete coverThe concrete thickness between the surface and the nearest bar.
- Reinforcement (rebar)Steel bars placed inside concrete per bar-bending schedules to strengthen structural elements.
- Pre-pour checklistChecking steel, formwork and services before a pour is approved.
- FormworkTemporary moulds that hold concrete until it hardens.
Read next
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