NCARB Practice Question - Perimeter Stormwater Management

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Robin Owens

September 23, 2023 16:13

Hello - One of the practice questions (52) asked where to place drainage tile for a residential building - my answer placed the perforated pipe at the top corner of the foundation footing exterior. NCARB counted this as an incorrect answer. Many books I’ve studied have shown images and descriptions for placing the drainage tile above the foundation footing - generally within a few inch variation. Can NCARB tell me why my answer was counted ‘incorrect’?

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  Christine Williamson Cronin September 23, 2023 16:26

  I’m not sure how ncarb will respond, but there are several acceptable places to put the perforated pipe, depending on the specific configuration. In all cases, though, the drainage should always occur below the level of the bottom of the basement slab. It doesn’t have to be below the whole footing, and it can be on either side of the footing (but usually it’s on the exterior side). I’ll attach a photo in a separate response.

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  Christine Williamson Cronin September 23, 2023 16:33

  Here's an image of what I described above from "Moisture Control for Residential Buildings" by Joseph Lstiburek.

  

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  Russell Forster September 24, 2023 18:13

  The above detail is the one I've been using for a hundred years...and I think it is still correct.  It will be interesting to see how NCARB responds.

  However, thanks to this great post, I went BSC and they have a new detail that slightly differs from the detail above (and I think it's from Dr. Joe Lstiburek, as well) showing the perimeter drain below the B.O. footing, which makes sense because it includes moisture from under the floor slab.

  Now I have to change my standard foundation detail :)

  

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