Tar Heel Tip Of The Week: What is Slab Settlement?

Monday, June 22nd, 2015 by Jaimie Hooker

Most likely…The soil has changed. And while there are many reasons the soil may change underneath your driveway, patio, garage or slab floor, listed below are the three most common reasons:

1. Changes in soil’s moisture content.

changes in soil moisture content

The Piedmont region of North Carolina is known for the bright red clay. Clay is a common soil type when clay is wet; it holds onto the water and expands in size when its dry it shrinks.

Imagine how drastic this is when several feet of clay soil exists below your concrete slab. In any case, the soil beneath your slab shrinks is size, it creates an empty space for the slab to settle into. The result? You’re left with a cracked an unleveled concrete area.

2. Wash-out of soil underneath of the slab.

Washed-out of soil underneath of the slab

As water moves beneath the concrete slab, soils can be washed away that is supporting the weight of the concrete. This can be caused by plumbing leaks, natural erosion, large rains and other reasons. When water is able to flow underneath the concrete slab area, soils will flow along with the water from beneath the slab. Over time with nothing to support the concrete, the slab will begin to sink or cave in.


3. Poorly Compacted Fill Soil.

Poorly Compacted Fill Soil

During construction of a home, driveway, patio or sidewalk, the soil is commonly moved around or spread out to get to the desired grade level. Oftentimes, the concrete slab is poured right on top of these fill soils that have been moved around. If the fill soil was poorly compacted, the fill soil compresses and settles, and a void is created under the concrete. With no supportive fill soil underneath the concrete cracks, breaks and settles into the void.


If you are experiencing slab settlement and would like a free estimate appointment, please call us.


About the author
Jaimie Hooker is the Assistant Marketing Director at Tar Heel Basement Systems; authoring case studies, technical papers, creating and captioning photo albums and managing website content. She also oversees the organization of video testimonials, shows and events, Jaimie lives in the small town of Madison, NC with her husband, Paul, and 3 year old son, Franklin.