Category: Structure & materials
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
Concrete cover is the distance between the outer face of a concrete member and the nearest bar. It protects steel from corrosion and fire. Typical code values: 75 mm for members cast against soil, 40 to 50 mm exposed to weather, 20 mm for internal slabs and 40 mm for internal beams and columns.
Why it matters on a project
Too little cover lets the steel rust so the concrete cracks and spalls years later, too much reduces the member's efficiency. It matters even more on the coast and in saline soil.
Measurement and pricing
Not priced on its own, but secured with concrete or plastic spacers, included in the steel or formwork item.
Worked example
A 40 x 40 cm column with 4 cm cover and 10 mm links: the space left for the main bars inside is 40 − 2 × (4 + 1) = 30 cm.
Common mistake
Laying steel directly on formwork or soil without spacers, so bars or rust stains show on the concrete surface.
Frequently asked questions
How do I check cover before the pour?
By checking the spacers and their spacing and measuring the distance at several points during steel inspection.
Can exposed steel be repaired after the pour?
The steel is cleaned, treated with a corrosion inhibitor, then repaired with a modified mortar, with the consultant setting the method for each case.
Related terms
- Reinforcement (rebar)Steel bars placed inside concrete per bar-bending schedules to strengthen structural elements.
- Reinforced concreteConcrete containing steel reinforcement to resist the tensile forces concrete alone cannot carry.
- Concrete grade (compressive strength)The characteristic compressive strength of concrete at 28 days, e.g. C30 or 300 kg/cm².
- Footings (foundations)Structural elements that transfer the building loads to the soil.
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