10 Steps to Integrated Foundation Moisture Control

Foundation Moisture Problems

Many brand new homes have foundation moisture control problems even though these problems are easy to prevent during construction. The moisture problems include the following.

  • Crawl spaces and basements become moisture sources by leaking water in from the surrounding ground.
  • Condensation happens on cool masonry floors, masonry walls, floor joists, and even floor insulation.
  • Water freezes beneath the footing, moving the foundation.
  • Mold grows on wet surfaces.

Poor drainage at the foundation's corners is a common cause of moisture problems like the mold shown here.
Poor drainage at the foundation’s corners is a common cause of moisture problems like the mold shown here.

Causes of Foundation Moisture Control Problems

  • Building basements and crawl spaces in wet soils or where the footing is below the historical flood plain.
  • Lack of waterproofing or dampproofing.
  • Lack of exterior foundation insulation.
  • Lack of a foundation drain.
  • Lack of proper drainage.

Preventive Measures

If you build new homes, prevent exterior water penetration by following these best practices.

  • Avoid building homes on crawl spaces, which are the most vulnerable type of foundation for moisture problems.
  • Use gravel base layers, free-draining backfill, and self-draining exterior insulation, where the ground is wet from seasonal precipitation.
  • Place polyethylene under slabs, and on top of crawl-space floors to prevent the intrusion of moisture, air, and soil gases.
  • Apply exterior waterproofing or damp proofing to the exterior concrete or wood foundation walls to restrict water and water-vapor transmission.
  • Use polyethylene, composite membrane, or rubberized coating to prevent water wicking from the footing to the foundation wall and from the foundation wall to the wood-frame floor.
  • Use a non-porous soil at the ground’s perimeter surface, and slope the ground away from the home at a 5% grade.
  • Drain water away from the home by using rain gutters, downspouts, and outfalls.
  • Apply proper flashing and sealing to all penetrations through the foundation and rim joist.
  • Install closed-cell polyethylene sill sealer to prevent capillary action between the rot-resistant wood mud sill and the masonry foundation.
  • Build footing drains so that they drain when they need to. A frozen outlet in the spring during snow melt may reverse the water flow toward the home rather than away from it.

Foundation moisture problems are persistent and difficult to repair. The extra money spent on the above preventive measures are well worth the cost.

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