Blinding concrete
Blinding concrete is a thin low-strength layer cast over prepared ground to seal the surface, give a clean working level, and protect reo before the structural pour.
Ask Chalkline about this →Blinding concrete is a thin layer of low-strength concrete (for example N20) cast over prepared ground or fill to seal the surface, provide a clean working level, and protect the reinforcement before the structural pour.
It is not a structural element. Its jobs are practical:
- Seal the surface: it stops the prepared subgrade from being churned into mud by rain or foot traffic, and stops the structural concrete losing water (and fines) into the ground, which would weaken the bottom of the pour.
- Give a clean, level working platform: reo can be fixed and spaced accurately on a firm flat blinding rather than sinking into soft ground.
- Protect the reinforcement and cover: bar chairs sit on the blinding so the bottom cover to the reo is reliable, instead of bars resting in dirt where cover and durability are compromised.
Blinding is common under footings, raft slabs, and pile caps, and on any pour where the subgrade is soft, wet, or uneven. Because it is non-structural, it is a low grade and a modest thickness (commonly around 50 mm), enough to do the job, not a load-carrying slab.
For a builder the practical points are to use blinding where the subgrade will not give a clean, stable base for the reo and the pour (it is cheap insurance for bottom cover and a tidy pour), to keep it thin and low-grade because it is not structural, and not to confuse it with the structural element, the design strength, cover, and reo all belong to the structural concrete above the blinding, not to the blinding itself.
Also known as: Blinding layer, mud mat, lean-mix concrete.
Category: Concrete / Footings.
Related
See also
References
- AS 1379 Specification and supply of concrete, Standards Australia (verified 2026-06-01)
Last updated: 2026-06-01. Verified: 2026-06-01. Quarterly review for currency.