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Keeping a storm room dry

user-2310254 | Posted in General Questions on

Because of a foundation SNAFU, I now have a storm room under my front porch. This thing will function as part of the conditioned basement space.

I understand that SOP is to install concrete over a galvanized metal roof and call it a day. Is this the best way to ensure the room stays dry. The porch is mostly not covered, and we can get a lot of rain in this part of the country.

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  1. user-659915 | | #1

    It should be pretty dry most of the time but not reliably enough to finish as conditioned space. You'd have to insulate under the slab as well as the walls and that would be problematic with even minor leakage. Just frame an insulated wall across between the part of the basement under the house and the part under the slab, with an insulated door so you could inspect it. And you'll still be able to use it as a storm refuge.

  2. user-2310254 | | #2

    Thank you, James. I'm sure you're right. I did find a couple of interesting product suggestions for keeping things dry here:

  3. GBA Editor
    Martin Holladay | | #3

    Concrete alone does not perform well as roofing. If you want the space to be dry, you need to include a waterproof layer on top of the concrete ceiling -- something like EPDM or a peel-and-stick foundation waterproofing product.

  4. user-2310254 | | #4

    Thanks Martin. That is the recommendation I'm getting from different folks who have been down this road. It seems to be particular important to detail the edge correctly. Covering the edge with EPDM or other waterproofing and extending the edge enough to allow the water to drip seem to be important.

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