By Sandford Tuey
An often-asked question is how much spacing should there be between rebar before you pour the concrete? Too wide of spacing, the cement / concrete mixture will not be as strong as it should be. Rebar spaced too close together and your foundation is also weaker than it should be. This is because there is too much metal to concrete mixture.
Setting rebar in the right place and distance apart, while keeping it secure during concrete pouring is crucial to the structure’s long-term integrity and lifespan. Your detailer will indicate the number of bars, bar lengths, bends, and positions. He/she will use the proper grade of wire to link the rebar together and keep it securely within the frames as your concrete is being poured.
An important reason for placing reinforcing steel properly is to ensure the right amount of concrete cover over the rebar. This is called ‘cover’ and is the amount of concrete between the reinforcing steel and the surface of the concrete. Cover is the single most important factor in protecting reinforcing steel from corrosion. Cover is important to assure that the steel bonds to the concrete to develop its solidity and strength. The requirements for minimum cover and spacing of rebar can be discussed by contacting a C & J Reinforcing specialist anytime.
More Cover Details
- Concrete cast against and permanently exposed to earth, as in footings, a minimum 3 inches above the rebar is needed.
- Concrete exposed to extreme weather or earth, such as basement walls, should use heavier rebar like #6 steel bars and a minimum of 2 inches apart. You may be able to get away with #5 bars or smaller. Ask your rebar professional.
- Reinforcing steel must be kept off the bottom or off the ground to increase performance. Use your detailer’s recommended method to support to keep the steel at the proper elevation.
- For concrete not exposed to weather or in contact with ground, slabs, walls, and joists: #14 and #18 bars a mini mum of ½ inch apart. Beams and columns, no less than 1½ inches apart. Before wiring rebar into position, contact C & J Reinforcing.
More Things to Know About Placing Rebar
- Spacing of bar supports depends upon the size of the reinforcing bar. For a solid slab using #5 temperature-shrinkage bars, elevate the rebar horizontally by a minimum 3 inches.
- Adjustment of the position of bars or welded wire reinforcement during concrete placement must not be permitted.
- The practice during slab construction of adding late reinforcement or pulling rebar up during concrete placement is called ‘hooking’. Try your best not to do this.
- Spacers for vertical concrete (wall construction) are optional. Adding spacers is more complicated than it sounds and should be done by a professional.
- An ironworker foreman, contractor, and inspector have the responsibility to ensure that the reinforcing bars in concrete construction are properly placed.