Since I have wet areas in the crawl space, I have decided to dig a trench at the perimeter of my crawl space to take care of the water. This would also allow me to install rigid foam insulation on the walls. The plan is to dig not only down to the footing but next to it down to its lower end but not lower. The dirt is wet here and there, but mostly dry and clay-like which makes it kind of hard to dig.

My calculations show that minimally I have to dig 110-120 cubic feet of dirt or around 900 gallons. I've bought 8 5-gallon buckets and 3 different sizes of shovels. I plan on hiring three laborers at $10/hour and renting a dump truck for $120/day. I will personally participate and manage everything. I'm hoping to finish within a day (or maximum two, although that'll be expensive).

Then, I will install a pipe in the trench which would be connected to an existing French drain system in the basement. Hopefully I'd be able to achieve a slope of 1/8" per foot for the pipe.

I'll also insulate the walls and cover with plastic but that comes later.

What do people think of this? Is this going to work? Anything I need to know?

Edit: The crawl space is adjacent to a basement. Both of them are 30x15 feet. There is a French drain system professionally installed in the crawl space (with a sump pump). At my request, they drilled through the footer at one corner to connect the system to the crawl space via a 2 inch PVC pipe which I'm going to connect to the crawl space perforated pipe. The basement is 7' crawl space is only 3' or so.

1 Answer 1


Your basic plan sounds workable. I assume your crawl space is adjacent to a full basement area? I have a couple of questions. Where does the existing drain tile system empty? Is there a difference in level between existing basement floor and footings of the crawl space? the answers to these questions may change my answer to you. But basically, adding a French drain or perimeter drain tile should help your situation. After your trench is dug, be sure to line it with several inches of gravel/crushed stone. Use perforated pipe with inlet holes or slots on only one half of the surface and be sure the slots are facing up when installed. Wrap the pipe in common landscape cloth before backfilling with crushed stone to prevent the drain pipe from filling with sediment. Lay another layer of cloth over the stone and complete the backfill with clean grave. Not sure how you plan to connect to the basement drain system, but that is another topic. This kind of work is always difficult, especially when working in a crawl space with limited head room. Good luck.

  • 2
    Thanks for verifying my plan. See my edit with answers to your questions. I'm doing the work at the moment :-)
    – Peter Q
    Commented Jan 15, 2011 at 15:20

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