Concrete – How big a hole do I have to drill in concrete to embed rebar in it

concretedrillholerebar

I have a concrete patio that I'd like to use as the foundation for a CMU wall. I'd like the CMUs to be tied into the patio slab with rebar. I get that the gist is to drill a hole in the slab, put rebar in the hole, and then fill it in with concrete to anchor the rebar into the hole. What size rebar should I use, and how big a hole do I need to drill? If I use 1/2" rebar, can the hole be 5/8"? 3/4"? Does it have to be 1"? etc.

Best Answer

It's been a long while since I worked construction, but I think I remember dowelling into concrete in a similar manner with a 1/2" drill bit and #4 rebar. We used a sledgehammer to drive the rebar pegs in. It MAY have been a larger bit, but I think I remember it being the same size.