[OP]
Member
The question for today is: How close to the top edge of a concrete foundation can you drill (1" hole is the target)?
I know there are rules regarding drill holes in floor joists (hole size, spacing, distance from edges, etc.) and assume there are rules for drilling concrete.
Member
Generally around 3" from the edge of the hole. If you are using some type of wedge anchor that will put a significant side force on the concrete, then 4" or more would be better.
[OP]
Member
My bad. Let me clarify. I'm looking to drill a 1" diameter hole completely through the foundation to pass through a piece of PVC tubing. I'm not looking to install anchors or screws, those require 5 or 10 diameters depending on the type.
Member
A one inch hole should not weaken the foundation no matter where it is drilled. The only thing is there should be rebar within 3-4 inches of the top of the foundation, if it was me I would drill 6" from the top and hope you do not hit a vertical bar.
Contributor
3" or so would also be reasonable if you're concerned with blowing out the material above the hole. Strength and the foundation is not an issue at all. My main concern would be drilling too close to the top and half way through the relish above the hole blows out.
Last edited by Chris Padilla; 09-22-2014 at 1:48 PM.
[OP]
Member
All of the above are concerns. I'm afraid of the blow out or chunking between the hole and the top edge. Thanks for the input.
Contributor
So say you drill close to the edge of the foundation, and you get some blow-out. What's the problem with that? You slide your PVC tubing into the hole, maybe stick it in place with caulk or construction adhesive, and you're done. As others have said, the small hole doesn't weaken the foundation, even if it blows out the side a bit.
Member
A 1" hole won't create any structural damage to your concrete foundation wall. But you may run into some rebar. Most residential foundations around here don't have any rebar but some do. You'll know it if you hit rebar. Everything comes to a halt.
If you want to minimize blowout, you can drill a 1/4" pilot hole straight through and then drill your 1" hole from either side. I've done it many times and it works like a charm. Also the type of hammer drill and bit you use makes a difference. Hilti makes some excellent bits that drill through concrete like butter and create little blow out, even without a pilot hole. You just have to go lightly when you hit the end. But those drills and bits are pretty expensive, unless you can borrow one.
Member
Is there a reason why you have to drill through the foundation? If you are drilling that high on the foundation why not go through the rim joist?
"The real voyage of discovery consists not in seeking new landscapes, but in having new eyes." - Proust
Moderator
A buddy recently purchased a brand new house that was built with pretensioned concrete throughout. You are not supposed to drill into that so we had to pour a small slab of concrete so that he could drill into that. Just an FYI.
Last edited by Chris Padilla; 09-23-2014 at 12:45 PM.
[OP]
Member
The porch's ledger board is attached to the rim joist and would be too high. I'm looking to install an electrical outlet on the corner post of the porch nearest the driveway. Coming directly out below the rim joist/sill plate/ledger board is the best location, but don't want to chance 'breaking' the foundation's concrete. I already have issues with the concrete the foundation is made of and don't want to create any new ones.Originally Posted by James Conrad
Member
Any time I've had to penetrate a wall to run power to the outside, I've taken the easy route and drilled through the wood, if possible. But there have been a number of occasions in residential applications where the situation required drilling through the foundation wall. I've drilled holes as large as 2-1/2" with a hammer drill without doing any more damage than a little blow out. Larger than that, we usually bring in a coring machine but even the larger holes don't affect the structural integrity of the concrete. That's true of both walls and floors (as long as you don't hit a tension cable). What issues exist that concern you enough to think drilling a 1" hole in your foundation wall will create more issues?
Last edited by Chris Padilla; 09-23-2014 at 12:43 PM.
Member
I've drilled concrete slabs before,and I would do it another way if at all possible for a 1" hole X 6-8" deep. Even to the point renting a core drill or hiring someone to do it would be beneficial.
You can walk with a wooden leg but you can't see with a glass eye - Always were Eye Protection!
Contributor
An SDS-Max drill, and decent quality bit will got through it easier than a wood bit through wood. The difference between the different sizes of hammer drills is astounding. I'd find someone that has an SDS-Max, if you don't have one, and give him a few bucks to pop the hole.
Member
I like my Black and Decker Macho II better than My Milwaukee USA 1 for drilling large holes
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