How to Select Rebar Supports and Spacers
Rebar supports and spacers are used to secure the reinforcing steel or rebar in reinforced concrete structures. Prior to the final concrete pouring, the rebar is assembled in-place with the rebar chairs, slab bolsters, or wagon wheels. These rebar supports are then left in-place while the concrete is poured.
Types of Rebar Supports and Spacers
There are three main categories of rebar supports and spacers: support chairs, slab boosters, and wagon wheels.
- Rebar chairs or rebar support chairs can be used to support lower and upper mats as well as rebar. They are made of plastic, typically high-impact polypropylene, and exhibit excellent chemical resistance. Rebar chairs come in larger sizes for placement over the lower bars in a mat, and are suitable for use either in epoxy-coated, black, or stainless steel rebar. Strong but lightweight, these concrete reinforcement products may qualify as CRSI Class 1 bar supports.
- Rebar slab bolsters are a type of continuous rebar support for use in cast-in-place and tilt-up slab and deck construction. Their arch-shaped design provides strength, while corrugations on the crossbar help with bar location. Larger-sized products have a sleeve that can be used for end-to-end connections. Like rebar chairs, rebar slab bolsters are made of plastic, and are strong but lightweight.
- Wagon wheels or wagon wheel spacers are used to space vertical or horizontal reinforcements in beams, walls, or columns. Sometimes called circular chairs, these rebar supports and spacers snap onto the rebar.
Rebar accessories are made of either metal or plastic. Typically, plastic products are gray or white in color to blend in with the concrete.
When selecting rebar supports and spacers, strength per unit of measure is a critical specification to consider, as it indicates how much force the accessory can handle. The Concrete Reinforcing Steel Institute (CRSI) maintains and publishes standards with which products may comply.