How to Install a Perimeter Drain Crawl Space

The crawl space, or open area underneath a house or other structure, provides convenient access to the underside of a house with no basement. However, if a crawl space is plagued by flooding or persistent moisture, it may develop structural problems or raise health concerns. Whether the crawl space moisture is caused by poor landscape drainage, a seasonally high water table or other factors, a perimeter drain can be implemented in the crawl space to alleviate the moisture problem.

Mattocks, shovel and other digging tools
Measuring tape
Level
Filter fabric
Perforated PVC pipe or other drainpipe
Gravel

Instructions

- 1
  Excavate a trench around the crawl space perimeter where the drain will be placed using a mattocks, shovel and other digging tools. The required dimensions for the trench will vary depending on certain factors. The trench must direct water to a sump pump, ditch or other outlet, so the trench must slope toward this outlet. Ideally, the trench should be at least a foot wide and 2 feet deep, but it can extend to the same depth as the footing.
- 2
  Check the bottom of the trench to make sure it decreases in elevation slightly toward the outlet or sump pump. Move earth around to make any corrections.
- 3
  Line the trench with filter fabric or landscaping cloth. The fabric or cloth will keep sediment from entering the trench and clogging the drainpipe.
- 4
  Lay the perforated 4-inch PVC pipe or other type of perforated drainpipe in the center of the trench. Check the pipe to make sure it slopes to the outlet or sump pump and make any necessary adjustments. Connect the pipe to the sump pump or ensure that it extends to a suitable outlet.
- 5
  Cover the pipe with 6 to 8 inches of clean, coarse gravel.
- 6
  Lay filter fabric on top of the gravel.
- 7
  Fill in the remainder of the trench with gravel or fill that was removed earlier.

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