Waterproofing porch over foundation

Old 11-18-10, 03:49 PM
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Waterproofing porch over foundation

My fiancée and I own a 95 year old home and are slowly chipping away at some of the improvements we want to make. This is my first post so bear with me.

We've got a small (approx. 8' x 8') covered porch in the back corner of the house. While most of the porch extends beyond the foundation, a portion of it (approx 8' x 4') sits directly above it, over the SE corner of our basement. Some rainwater has been seeping into the basement and is visible on the joists near that corner. I want to tackle sealing up that area over the basement from the elements.

I need to pull up the decking that is over the foundation (it's T&G) and then waterproof that area beneath the decking to keep moisture out of the basement. I'm looking for suggestions on what the best approach would be, short of closing in the porch. One suggestion I received was to use a waterproofing membrane beneath the decking.

Happy to provide more details as needed.

Old 11-18-10, 05:44 PM
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Welcome to the forums! Since you can see what you have and we can't, help out some of the more feeble minds on the forum to envision it. You can post photos on a site such as photobucket.com and copy/paste the IMG code to your repy post. That way we will have a better starting point.
Old 11-19-10, 03:20 PM
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The membrane has to go against the foundation. That means you have to expose the foundation one way or another. If you are willing to remove the decking, then dig against the house to the footing, you'll be able to seal it. That's not an easy task when you are working below the frame of the deck.
Old 11-20-10, 09:50 AM
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Hi Venkman781:

You said that you can see the water on the 'joists'. If you mean the basement ceiling joists, does that mean the water is entering your house above the foundation?

Several houses ago, I had water seeping through the lower house siding from a porch surface that allowed water to 'pool' against the house. I had to fix that problem by changing the pitch of the porch to allow water to drain away from the house.

You might also check the soil below the deck to be certain that it slopes away from the house. With the right slope on the soil, a waterproof membrane on top of the soil and fastened up to the base of the porch might correct a small problem. For a serious problem, you need to follow Pulpo's recommendation and seal the membrane to the cleaned foundation.

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