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An Unsettling Problem

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    Harry Whitver

    Serious Settling

    Multiple and growing cracks in foundation walls and single- and double-hung windows that are racked beyond use are telltale signs of a settling problem well beyond the norm. The problem is likely far below grade, where improperly compacted and/or unstable soil content and perhaps an intermittent intrusion of moisture are causing the foundation and footings to sink or heave.
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    Harry Whitver

    Compact Better

    Get a soils test and engineer the right foundation for the site’s conditions—including the “influence” depth, the distance between the top of the footing and the weight felt by the soil particles below. Clear out any organic matter, and compact the soil in layers of 8 to 12 inches deep to one-half the influence depth. If necessary, amend or reinforce the soil to stabilize it.
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    Harry Whitver

    Mitigate Moisture

    Take advantage of a high site to facilitate water drainage away from the foundation in all directions. For a low-level site, add a more active runoff system, and consider a vapor barrier under the slab or on the exposed soil to block moisture. Add expansion (or control) joints every 8 feet to attract cracks. Little ones are okay, especially in a control joint.

All houses settle, some so little or so evenly across the foundation that the effect is imperceptible and inconsequential to the quality and livability of the house. Others are obvious, creating noticeable cracks in the foundation and above-grade walls and ceilings, causing windows and doors to rack, and resulting in sloped floors. Cracks and racking also likely undermine any attempts to reduce a home’s energy consumption, working against an air-sealed and insulated building envelope.

Obviously, fixing the problem is a lot harder and more expensive than spending a few extra days and dollars to properly compact the soil under the foundation footprint and engineer a slab or basement for your site’s soil conditions.

A soils test, specifically a soil bearing verification test conducted by a state-certified engineer, will tell you most of what you need to know. The rest is making sure your trade partners—from the compaction contractor to the concrete supplier and the foundation sub—do their jobs with attention to detail and tight tolerances to ensure that when the house settles (and it will) that the impact is minimal and all but unnoticed.