Proper Drainage...

Originally Posted By: bnelson
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A local builder came by my place the other night, quite late I might add, in a panic because two of his 9 spec homes’ crawl spaces had turned into swimming pools with the recent rains. Sump pumps for sure, but I’d like to provide him with some illustrations from authoritative sources on the proper method and placement for rigid perforated pipe. His excavator lays it on top of the footings, whether he bothers to put the holes down I don’t know. But these are hillside houses and I should mention that these crawl spaces, and ALL crawl spaces in this area are the lowest grade on the site. They get backfilled, if at all, about an inch above the bottom of the footing (on the interior of the crawl space.) Stupid, I know.


Originally Posted By: mkober
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Brandon,


I don't have the illustrations you're looking for, but I can describe what a reasonably prudent builder SHOULD be doing:
1. Extra deep drainage swales on the uphill side of the house.
2. Two circuits of perforated drain lines, one outside, one inside.
3. Exterior drain line pitched to daylight (sloped lots, right?).
4. Interior drain line run to sump pit, with high output pump(s).
5. All drain lines pitched at 1/4" per foot, bedded in and covered with washed rock and filter fabric before conventional backfill.
6. Consider paving the crawl spaces.

Obviously the foregoing, with the exception of number 1., are going to be pricey for homes already built. Just remind the builder that houses with soggy crawl spaces can be very difficult to unload.

Michael J. Kober, P.E.


Originally Posted By: bnelson
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Excellent. Thank you, Michael. I did find a contractor in the WA area that has several good diagrams on their site: http://www.bodineconstruction.com


Originally Posted By: dvalley
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Brandon,


I believe this may be what you are looking for.

![](upload://me4MtRe3nGBGET8vgZY42XGj9kl.gif)


--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."