Remodeling Tips and Reviews

How to pour a concrete slab next to an old slab

How to pour a concrete slab next to an old slab

Feb 21, 2012

We have all seen slabs of old concrete where the two slabs meet and one has settled and the other has heaved over the years. This happens because the concrete likely did not have rebar in it and, as a result, moved apart as it fractured.

Pouring concrete is not rocket science, but there are a few things that need to be done when butting an old and a new slab next to each other. In order for concrete to properly distribute the load on it, dowel rods need to placed on the side of it to help maintain an even surface load from one slab to another and keep the slabs from heaving in relation to each other.

This is done using a hammer drill, dowels and epoxy, which is specially formulated for concrete. The dowels should be positioned about 8″- 12″ apart and centered in the concrete vertically.  You will need a concrete bit and a good hammer drill to drill minimum 6″ deep holes.  If you are using #2 rebar than you will want a drill bit that is at least 1/8″ bigger. I suggest a long 3/4″ concrete bit. Once all the holes have been drilled you will want to blow them out with air to clean out all the dust. Then start injecting each hole with a shot of the epoxy and push the dowel in place. Once they are all in, allow the epoxy to set up over night and then you are ready to pour the slab next to this one. This also works for slab over slab and cut out repair jobs where you had to cut out an interior section of a slab and repour it.

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