Bar chair
Bar chairs are plastic or steel supports that hold reinforcing mesh at the correct height before concrete is poured, maintaining the required concrete cover.
Ask Chalkline about this →A bar chair (also called a reo chair or concrete spacer) is a small plastic or steel support placed beneath reinforcing mesh or bars before a concrete pour. Its purpose is to hold the reinforcement at the correct height above the subgrade or vapour barrier so that the required concrete cover is achieved on the underside of the steel.
Under NCC 2022 ABCB Housing Provisions clause 4.2.11, bar chairs must be spaced at no more than 800 mm centres for steel fabric. The minimum cover maintained by the chair is 30 mm where a vapour barrier is present, or 40 mm where the concrete is in direct contact with unprotected ground (clause 4.2.11(5), verified 2026-05-10). On soft ground or plastic membranes, chairs must be placed on flat bases to prevent them from punching through the barrier.
The most common pre-pour defect on residential slabs is mesh sagged off its chairs from workers walking on the reinforcement without plywood or board protection between pours. The certifier checks chair height and spacing as part of the mandatory pre-pour inspection. Sagged mesh significantly reduces concrete cover and accelerates reinforcement corrosion over the building’s life.
Also known as: Reo chair, plastic spacer, concrete chair, wire chair.
Category: Structural / Reinforcement.
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Last updated: 2026-05-10. Verified: 2026-05-10. Quarterly review for currency.