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Slab Settlement and Why it Happens

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What exactly is slab settlement?

Slab settlement is simply the movement a concrete slab experiences when the soil underneath it can no longer support the weight of it.

Soil changes – that is why your concrete will begin to sink and settle. Let’s focus on the three most common reasons why a concrete slab will settle.

1. Changes in the soil’s moisture content

Two very common soil types are sandy soil and clay soil. Sand is not greatly affected by moisture, but it does eventually wash away.

When wet, clay holds water and expands in size; when dry, it does the opposite…it shrinks. Soil dries out for many reasons: drought conditions, tree roots taking up all of its moisture, and leaking HVAC systems under your floor slabs. When soil beneath your concrete slab shrinks, it creates empty space for the concrete slab to settle into. This creates cracks and unleveled concrete.

2. Wash-out of soil under the slab

As water moves beneath your concrete slab, it can wash away the soil supporting the concrete. This is caused by plumbing leaks, erosion, large rains, and numerous other reasons. If water continues to wash underneath concrete, it will eventually leave nothing left to support the concrete…resulting in sinking and caving.

3. Poorly compacted fill soil

When a home is being constructed, the soil is usually moved around or spread out to make sure the whole plot is at the desired grade level. When the concrete slab is poured on top of this loose soil, it compresses and settles the soil. When the soil moves like this, it causes concrete to crack and sink.

Many issues such as these, and others might be affecting your home or commercial structure. The foundation specialists at Aquaguard will be able to diagnose these issues and more with a free written evaluation and in-home foundation inspection . Call or contact us today.

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