Foundation collapse, repair (C) Daniel Friedman The Main Causes of Buckled Foundation Damage in Wet, Freezing Climates with Clay Soils

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Role of frost, freezing, & clay or wet soils in foundation heaves, cracks, damage: this article explains the main causes of foundation cracks, buckling, or collapse in areas of freezing weather, clay soils, or wet soils. We provide suggestions for avoiding foundation damage or collapse in areas of freezing climate, and we discuss the proper foundation insulation locations and materials for use in problem areas. In this article series we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. Photo (above) shows a new foundation constructed below a New York home after a catastrophic foundation collapse caused by wet soils.

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What is the Main Cause of Foundation Failures in Clay Soils?

Buckled building foundation (C) InspectAPedia.comMost foundation failures in clay soil have nothing to do with freezing. The culprit is more often the expansion of the soil when it absorbs water.

In Fargo, said housing engineer Lambert Vogel, when the soil dries out and shrinks, it can pull away from the foundation as much as two inches to a depth of three feet or more.

Either the wind or the homeowner is likely to fill this crack with loose soil. When the clay soil gets wet again and expands, crack goes the wall - if it is weak.

In some areas of expansive clay soils such as portions of Colorado, builders install a soil watering system below the building's foundation and slab in order to prevent this clay soil shrinkage during dry weather.

Readers who need to diagnose the cause and decide on the cure for foundation damage should start at FOUNDATION CRACKS & DAMAGE GUIDE. Readers should also see BASEMENT HEAT LOSS for a discussion of basement and foundation insulation. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

Recommendations to Avoid Foundation Wall Cave-Ins in Cold Climates

Vary rarely do foundation walls cave in from insulation, except possibly in Duluth, Minnesota, where all the conditions are ripe for foundation failure: lots of rainfall, clay soils, very cold winters, and building practices that often do not include foundation drainage to assure that soils close to the building foundation are not water-saturated.

But you can prevent all frost-related foundation damage problems by following standard good building practices:

  • Provide positive site drainage - do not direct surface or roof water spillage against or close to the building foundation
  • Use granular backfill or gravel around foundation walls, including footing drains that carry water to daylight well away from the building
  • Build foundation walls strong enough to withstand unavoidable intermittent pressures and loads exerted by water or ice.
  • If your foundation insulation is to be installed on the outside of the wall, use a material such as Styrofoam that will not lose its insulating value when exposed to moisture or water.
  • If your foundation insulation is to be installed on the inside of the foundation wall, we still prefer using insulating foam board products such as high R-value urethane foam boards rather than fiberglass insulation. That's because fiberglass against or close to a below-ground-level building foundation is exposed to moisture from both the building interior as well as from the building exterior. Moist or wet fiberglass insulation not only loses its insulating value, but it can become a problematic mold reservoir in the building. (See FIBERGLASS INSULATION MOLD.)

Given basically sound foundation and site work, it is acceptable to insulate a building foundation inside (giving up the thermal mass benefits to the building) or outside, and to install foundation wall insulation half-way, full-height, or flared-out - anywhere in the continental United States.

In foundation insulation retrofits in very cold climates, life is not so simple. What if you have an un reinforced concrete block foundation, a frost-susceptible soil (clay or silt), and poor site drainage? Then we would be reluctant to install any foundation insulation without first correcting the site - at the very least by conducting surface water and roof spillage well away from the building foundation.

Where the integrity of the foundation wall is in doubt, there are compromise solutions. We might install half-height insulation on the inside of the foundation wall, or half-height insulation n the outside of the foundation wall with the addition of at 2- to 4-foot flare. But don't expect good thermal performance with half-height interior foundation insulation on an open-core concrete block foundation wall. Convection in the concrete block cores will carry heat right past the insulation.

Also consider the wintertime temperatures in the basement or crawl space. If the building owners have insulated the basement or crawl space ceiling, and are heating with a woodstove upstairs rather than a furnace or boiler in the basement, the basement walls, not to mention the water pipes (see WINTERIZE A BUILDING), could get very cold.

Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

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