Concrete porch over basement

Old 01-05-08, 04:16 PM
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Concrete porch over basement

We have a 10-year old house built into a hill with a basement garage. The front porch is concrete and extends the full length of the house (about 36' by 8' deep). There are three small rooms in the basement directly under the porch. We've never used them for much because they occasionally get water when it rains. There are cracks in the concrete porch where the concrete meets the bricks at the edge. I caulk it occasionally, but eventually the caulk cracks and more water leaks into the rooms below.

We're wanting to use those rooms more, so I decided to look above the plywood ceilings in these rooms to see if there was any mold, etc. Boy was there! So I called in the mold remediation specialist. When he started tearing out the ceiling, he discovered that the concrete porch was laid directly on to (soaking wet) mdf board, which was sitting on (wet) joists. He took out the ceiling, the mdf board, and the joists. So now the concrete porch is supported by boards around the perimter and the cement block wall on the house-side of the porch.

Long story, looking for what I should do next. I already have an appointment with a guy to put Permacrete on the porch to permanently fix the water entry problem. The mold guy thinks that the concrete is strong enough to support itself, but recommends a steel beam around the perimeter just to make sure.

Not sure how thick the concrete is, but can it hold itself up? Should I be afraid of walking underneath it? Does anyone have any links to how this porch should have been constructed in the first place?

Glad that the mold is gone, but a little nervous about he missing joists.

Thanks for any pointers,
Old 01-06-08, 06:12 AM
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It depends on what's in the slab. If they poured a substantial rebar grid in there, it would probably hold up okay. If it is not reinforced with rebar, I would be afraid of it falling at some point.
I would also be more comfortable if instead of a steel beam around the perimeter, there was a central beam running the length of the porch. A 4' span would be a lot more stable than an 8' one.
Also, when you say Permacrete, are you talking about a thin cementious concrete coating? If so, make sure he warranties it not to crack, and look for the term "waterproofing" in the contract. Most coatings like this were developed to cover cosmetic defects and make the concrete look better. However, they will crack in the same places that the concrete is already cracked, negating their waterproofing capablities. I see it all the time on decorative concrete overlays. Maybe the Permacrete you're talking about is a different product though. Good luck!


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