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milkweed
drilling hole through concrete basement wall
milkweed

Our house is a ranch with a full basement.
The basement wall appears to me to be cast in place that is 6" or maybe 8" thick,
the beam pockets are 4.5" deep.
Above the basement slab, I measure the wall to be 7'6", so an 8 foot wall?
The beams are (3) 2x10 lumber nailed together.

Our house has a geothermal unit that pumps out of one well and dumps into
a different well in the yard on the opposite side of the house.
Pictured is the side of the basement the discharge pipe is routed through the wall.
It is my intention to convert the geothermal unit to a closed loop.
In one design of the loop, I would need to drill two new holes that are
about 1 foot above the basement slab through the concrete wall that are
3 inches in diameter.

Are there any considerations of where not to drill a hole through a
cast in place concrete basement wall, or a limit to how large a hole can be drilled?

In one of the two images I will post, I drew in two red circles where I think
I might want to have the pipes go through. MMM, it is rejecting my images.
Is there a concern for drilling (vertically) beneath the beam pocket like
previous owners had done for the discharge pipe?
... does the hole near the pocket weaken the wall for supporting the beam?

Fencepost
Re: drilling hole through concrete basement wall
Fencepost

You'll need to post the pics to some photosharing site (like Photobucket), then post the links here.

As for the holes, for what you're wanting to do, you can pretty much put them anywhere. You might end up cutting through some rebar, but that shouldn't cause structural problems if the wall is well-built otherwise. Your best bet is to hire a concrete-cutting company to come and drill the holes for you or your contractor using a core drill. They will make a nice, clean hole with no blowout that will be easy to reseal. (I am not an engineer and accept no responsibility for any structural damage that may occur. You may wish to contact a structural engineer or a properly insured and bonded contractor for advice.)

Of greater concern to me is that the wall be properly sealed after the pipes are installed. If the holes will be below grade, it's even more critical.

milkweed
Re: drilling hole through concrete basement wall
milkweed

Thank you for that reply.

I had read one user on a forum suggested RTV silicone, but later was reading a manufacturer of engineered concrete wall panels say not to use silicone, but rather a urethane sealant ... that it will last longer and be able to flex more if needed. One set of instructions said to coat the outside wall with hydraulic cement to shed trickling water (in addition to the sealant in and around the wall). Another set of photos a geothermal HVAC company posted ****** showed some sort of tar on the outside wall, which I'm not familiar with what hydralic cement looks like so maybe that was the same they were working with. Needless to say, it is another aspect I plan to research a lot. Thanks again.

Mastercarpentry
Re: drilling hole through concrete basement wall
Mastercarpentry

I don't like introducing chances for water to enter a house unless that's necessary. Unless there's something giving trouble with your open-loop geothermal system I'd leave it in place as the changes you're thinking about are going to be expensive and will probably not amortize for decades as opposed to years. But anyway.

The polyurethanes I am familiar with are not very flexible although they adhere very well. The sand in the concrete is silica which is what burned silicone reverts to, so I can't see any compatibility issues using silicone; in fact that would be my chosen sealer if there's any chance of shifting or of differential expansion rates. While the holes will probably not affect structural strength it might be a good idea to call in an engineer to look at that as well as to recommend the best way of sealing the penetration afterward, plus to give you any additional thoughts they may have regarding potential problems we may not be aware of.

Phil

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