Bar supports keep reinforcement off the subgrade or form face so it ends up with the cover the drawings call for. Chairs come in set heights such as 1.5, 2 and 3 in, with variants like slab bolsters, high chairs and plastic-tipped chairs for exposed surfaces. Too few and the mat sags when crews walk it; the wrong height and the cover is wrong for the life of the structure.
Put a chair every four feet under the bottom mat, the inspector already flagged bar laying on the vapor barrier.
Also heard as
- bar chair
- bar support
- high chair
- bolster
Related terms
Cover
The depth of concrete protecting the outermost bar, measured from the bar to the nearest face.
Dobie
A small precast concrete block, often with tie wire cast in, used to hold rebar up off the ground.
Rebar
Deformed steel bar cast into concrete to carry the tension that plain concrete cannot.
WWR
Welded wire reinforcement, a grid of steel wires welded at every crossing and sold in sheets or rolls.
Vapor retarder
A plastic sheet under a slab on grade that slows ground moisture from rising into the concrete.