Is damp proofing interior of garage foundation walls required?
AGoldstein
| Posted in General Questions on
I’m building an addition for a client and the concrete contractor let me know damp proofing the interior of the garage foundation walls is required by code. I looked at the code and it doesn’t specify whether to dampproof the outside or inside. I’ve seen this done on the inside of another garage in a different town in the same state (MA) and it didn’t make sense to me. Could someone please explain why the garage foundation should not get dampproofed on the outside just like the rest of the house foundation?
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Replies
AGoldstein,
"Could someone please explain why the garage foundation should not get dampproofed on the outside just like the rest of the house foundation?"
We damp-proof on the outside here. I'm at a loss for why the inside would be a better option.
AGoldstein,
The only times I have seen dampproofing applied at the interior (or a garage, crawlspace, or basement) are when the building has already been built, and then the water/moisture problem has to be dealt with retroactively. I can't imagine how it could be any easier or cheaper to dampproof from the inside, and even then you are letting any moisture move through the concrete first, rather than stopping the concrete from transmitting moisture in the first place.
I'm not sure if this is a good gauge of how uncommon dampproofing on the interior is, but when I Googled "dampproof interior of foundation wall" this thread is in the top ten results, and this thread has been around less than a day.
That was my thought too Paul. Better to stop the water before it enters the concrete. I called the building department and the inspector said dampproof the exterior. I had already done one wall on the interior though. I did the rest on the exterior. My concern now is if I do the exterior of the wall that I dampproofed on the interior the concrete may have a harder time fully curing. But maybe not. It was poured last Thursday.
AGoldstein,
All I can think is that maybe your contractor is misinterpreting a requirement that the damp-proofing should be continuous around the perimeter of the house, which as Adam in post #3 says should include the house wall in the garage?
Water accelerates the curing of concrete. I would think damp-proofing both sides would keep the water in.
Dampproofing the garage/house wall on the garage side face is standard practice in my SW Ontario market. In the end it's a cost saving measure as the garage/house wall is a far shorter distance that the entire perimeter of the garage but the logic makes sense to me that it should be fine.
I think it's much better to keep water out of the masonry, so damp proofing on the exterior should be preferred. Usually anything done to deal with water on the INTERIOR is something done as a retrofit later after problems are encountered. In new construction, I always recommend going things by best practice, and I'd consider dam proofing on the exterior to be the better way to go.
Bill
Damp-proofing is not the same as waterproofing. The purpose of Damp-proofing is to prevent moisture from moving due to capillary action. If you don't have a capillary break between the footer and the wall moisture can move up the wall from the soil below.
Are you sure the primary purpose is to prevent capillary action? The common bitumen and delta ms seems to be more concerned with moving bulk water down the wall plane and into the foundation drain than it does stopping moisture from diffusing through the wall.
I agree that dampproofing an waterproofing are different and the OBC treats them as such. In a nutshell though, the goal of both is to prevent water ingress.