Foundation Concerns From the Clay Bowl Effect

How the Clay Bowl Effect Starts

Moisture is an essential element to soil-it's a lubricant that traps air and allows soil particles to slide together. Too much moisture and the ground becomes muddy and unable to bear weight. Too little moisture and the soil breaks into its individual particles and blows away.

Dry soil also decreases the depth of plant roots because the plants spread out shallow roots in an attempt to absorb as much moisture as possible. This means that our yards are more delicate, our trees start to wither and provide less shade, the soil around our homes starts to blow around, and many of our plants produce less. All of these factors cause our yards and homes to feel hotter and our allergies to act up more frequently. We also start noticing burned patches in our grass and brittle leaves on our plants. In an effort to counteract these issues, we water more. For some reason, this doesn't seem to help.

That's because most of us are also battling a layer of hardened clay underneath the grass, which is literally siphoning the water to the nearest permeable soil. Unfortunately, the end result can be that the water intended for your grass is being forced into the ground beneath your foundation-this is called the "clay bowl effect". It works like this: homes are built by digging out, or excavating, a hole where the foundation will go. Naturally, this hole has to be wider than our foundation because people and machines also need room to work. Once the foundation is poured and dried, backfilling is done. In other words, the hole is filled until it is level with the virgin soil surrounding the construction site. This backfill is compacted, but it is literally impossible to compact it enough to match the density of the undisturbed soil in the lot.

Now, your home is built on top of the foundation and landscaping is completed. Over time, the entire lot compacts, but the backfill zone remains looser than the other soil. Water is more easily absorbed by loose soil, so your lawn could be burning, while the water is literally siphoning into your foundation. If you're battling dry patches, don't assume more water will solve the problem. Under your home could be wetter for your effort.

Here are the events that occur as water sits beneath your foundation:

1. Water causes expansive soils to swell and hydro-compactable soil to sink.

2. Back-filled soil is looser, so this soil moves more freely, increasing stress on foundation walls.

3. Pressure from exterior soil, as well as water pressure, weaken joints and widen existing cracks.

4. Water under the foundation traps radon, creates uneven soil moisture, and leads to many other problems

Some ways to tell if the Clay Bowl Effect is contributing to your Structural Problems:

--You have existing cracks in your foundation that weep water.

--Your basement has a higher relative humidity than the rest of your home.

--You have elevated radon levels and cracks in your foundation.

--You have struggled with mold problems in the past.

--You notice that your basement walls and/or floors appear dark in spots.