Serving El Cajon and Nearby
Free concrete estimates for homes in El Cajon, CA and nearby.
Clay Soil and Concrete Cracks
Clay soil and concrete cracks go together in parts of San Diego County. Wet clay swells, dry clay shrinks, and the slab on top pays the price.
At a Glance
- Expansive clay swells when wet and shrinks when dry.
- The County maps it in the coastal plain, valleys and foothills.
- Base depth, steel and joints help a slab ride it out.
- Walls and foundations call for a soils report.
What Expansive Clay Does
Some soils hold clay that soaks up water and swells. When they dry out, they shrink. The County calls these expansive soils, or shrink swell soils. Each wet and dry cycle pushes and pulls on whatever sits on top.
A concrete slab is stiff. It does not bend with the ground. So when one side lifts and the other sinks, it cracks.
Where It Shows Up
A County report says highly expansive soils occur mostly in the coastal plains, and also in valleys and on foothill slopes. It names the areas near Ramona, Escondido, Rainbow and northeast of Vista. You can read it in the County geology and soils report.
That report does not rate single lots. To see the soil under your own home, look it up on the USDA Web Soil Survey, or ask for a soils report.
Signs the Ground Is Moving
- Cracks that grow wider each season
- One side of a crack higher than the other
- Gaps opening between the slab and the house
- Doors or gates that start to stick near the slab
- Puddles that collect in new low spots
How Good Prep Helps
You cannot change the soil, but a contractor can plan for it. A deeper packed base spreads the load. Steel bars or mesh hold cracked pieces together. Control joints give the slab planned lines to crack along.
Water control matters just as much. Point downspouts away from slabs. Keep sprinklers off the edges. Slope new concrete so water runs off.
Walls and Foundations Need More
For a retaining wall, a foundation or a slab that holds up a structure, ask for a soils report. An engineer can say how deep footings need to go and what the soil can carry. A contractor should not guess on those jobs.
Freeze and Thaw Is Not the Issue Here
Much of what you read online about cracks comes from cold places. Ice inside concrete breaks it from within. That is not a San Diego County problem. Here, the soil and the water under the slab do most of the harm.