What is Slab Bolster?
A slab bolster is a small support that holds rebar at the correct height inside a concrete slab before and during the pour.
Definition
Purpose
The concrete cover over rebar helps protect it from moisture and corrosion. Bolsters keep that cover consistent from one end of the pour to the other, so no section ends up under-reinforced. Without proper support, the rebar can move out of position. This can affect the bond with the concrete and leave the slab below its design requirements.
Examples of Use
- Concrete Floor Slabs: Keep rebar grids at the right height throughout the pour to ensure the slab has a consistent concrete cover.
- Bridge Decks: Keep reinforcement in place during the pour to help crews maintain the positions specified in the design.
- Industrial Floors: Heavy rebar in high-load slabs requires bolsters rated for the bar size and spacing involved.
- Elevated Slabs: Keep reinforcement in place as wet concrete is placed and consolidated around the grid.
Notes
- Plastic slab bolsters work well in outdoor or wet areas where steel supports may rust and stain the concrete slab surface.
- Steel slab bolsters are better for heavier rebar layouts where lighter supports may bend under the load.
- Bolster height should match the concrete cover specified in the drawings and be checked before the pour.
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