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Community and Q&A

Drain tile – Slab on grade

Seth Holmen | Posted in General Questions on

I’m building an elevated slab on grade house. I am elevating the slab about 3 ft. above grade and using simple frost walls for the foundations. The site is very flat and does not have any obvious ground water issues.

I’ve dug two test holes (4 ft. deep), once last fall and one this spring and there were both dry. Is a drain tile required or highly recommended in a detail like this? I am not able to pitch it to daylight if a drain tile is located along side the footing.

Thoughts?

Thanks.

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Replies

  1. User avatar GBA Editor
    Martin Holladay | | #1

    Seth,
    As long as you address capillary moisture (with high-quality sill seal between the concrete and the mudsill, and with polyethylene under the slab), you should be OK.

    That said, I think it's always a little more gracious for a house on a flat site to sit on a small rise. You should save enough excavation soil, or buy enough extra topsoil, to be able to grade the site adequately, with the slope of the grade leading away from the house.

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