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Community and Q&A

No footing, no drainage?

Mike M | Posted in Building Code Questions on

Yesterday I was excavating a corner of my house to add Roxul to the exterior of my slab on grade foundation walls to help with my hydronic heat problems.

To my amazement, I found a section the foundation wall that has no footing. It is where the garage footing meets the house foundation wall. There is a corner and the house side of the foundation wall is missing a footing for about 2 feet. After this you can see the wood they used to form it go back below grade where I’m assuming a footing starts for the rest of the wall.

1. Is this normal to have this opening to allow drainage under the slab or something? Again this is about 36″ or more below the slab surface.

2. Will I cause any problems by adding schedule 10 drainage since the drainage now is garbage?

3. Since 95% of the foundation wall is below the slab level, would it help to add a waterproofing coat for any reason? I understand beneath my slab is not habitable, my biggest concern is rusting of the steel that is exposed in the foundation or having higher interior moisture. I figure once the exposed steel is rusted water will make its way into the concrete which will eventually spall it as the rust expands the steel.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Michael,
    I don't think it's worth adding asphaltic dampproofing or drainage pipe to the foundation stemwalls around a slab on grade -- but I'd be interested to hear if any GBA readers feel differently.

  2. Mike M | | #2

    Martin,
    Thanks for the response. I was figuring there was no real need for waterproofing. As far as drainage I'd like to add it because the corner of the house floods every rain. We have heavy clay and I've found termites in that area and was hoping drying it out and Termidor would help keep them from getting in. That colony has since been baited and eradicated.

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