The Ultimate Guide to Expansive Soils

The Ultimate Guide to Expansive Soils

Expansive soils are a geographical issue which, if not accounted for, can lead to expensive foundation repairs. This article aims to educate you on the “who,” “what,” “why,” and “how’s” of expansive soils.

 

 

  1. What are expansive soils?
  2. Why are expansive soils an issue?
  3. How do I know if my house is – or will be – affected?
  4. How to use USDA’s Web Soil Survey to find native soil characteristics for my house/property?
  5. What to do if expansive soils are encountered?
  6. What can I do to maintain my soils?

 

What are expansive soils?

Expansive soils are a clay soil type which is prone to large volume changes (shrinking and swelling) due to changes in water content.

Why are expansive soils an issue?

Expansive soils will expand/swell when wet, and shrink when dry. The constant cycle of shrinking and swelling can lead to repetitive stress on a structure. If left unaddressed, this can lead to cracks within the foundation slab, basement or upper-level walls, or damage to the exterior facade. As with most foundation issues, the repair costs are often extremely high.

How do I know if my house is – or will be – affected?

For those living on the east coast, midwest, and most of the western part of the United States, you need not worry about expansive soils. However, for those located in the plains states, Texas, or parts of the southwest, you may want to do a bit of research on your native soil types.

 

The map shown below is from geology.com and depicts the at-risk areas of expansive soils in the United States.

 

 

The map above will give you a general idea of if your specific region is susceptible to expansive soils. But how does one find more specific soil information for his or her own home or property? Below I will walk you through the steps of how to use the USDA Web Soil Survey. This information is also included in a Parcel Report, which can be produced for your own home or property through our online store.

How to use the USDA's Web Soil Survey

On the USDA Web Soil Survey homepage, click on the green button which will begin your web soil survey session. 

After clicking on the green button, you will be redirected to this page in a new tab. On the upper-left section of the page under “Quick Navigation”, click on Address and plug in the address of your home/property and click “View”. 

From the screen above, use the magnifying (+ and -) tools on the top toolbar to navigate to your home/property and ensure that you are adequately zoomed in, with the whole Property pictured within the viewing panel.

For the purpose of this example, I will be using small tract of residential houses in the Dallas area. For the purpose of your own investigation, it helps to select your own property, plus some of the surrounding areas. This will give you a better idea of the site specific soils in your area.

Use the AOI (“Area of Interest”) tools to select your property. For this example, I chose to use the rectangular AOI tool. The triangular tool allows the user to select a non-rectangular area of interest.

After your AOI is selected, click on the “Soil Data Explorer” tab at the top of the page. Then below, click on Suitabilities and Limitations for Use –> Building Site Development and select your property type. In this example, I chose “Dwellings with Basement (TX),” given that my property is located in Dallas, and I am assuming it has a basement.

Click on View Rating and the web soil survey will bring up a color-coded map, with descriptions below of the soil characteristics and limitations.

Yellow = Somewhat limited site soils.

Red = Very limited site soils.

In the example above, you can see that soils on the western and northeastern portions of the AOI are somewhat limited due to high shrink-swell and depth to soft bedrock. Soils in the eastern half of the AOI are very limited due to high-shrink-swell and depth to soft bedrock

What to Do if I Expansive Soils are Encountered?

Here are some things you may want to look for at your own home or property:

1. Visible foundation cracks – Check the basement area (if present) and the exterior foundation walls. Take photos of any cracks you see. I wrote a separate article dedicated to foundation cracks, check it out here!

2. Door and window frames – An early indicator of foundation movement is often found by inspecting the doors and windows. As the foundation/framing shifts over time, some doors and windows may not close easily. Check the doors and windows throughout the house to ensure that they are functioning smoothly and properly.

3. Exterior Damage – Check the building exterior for any cracking, movement, etc. Typically, cracks will form around window and door frames.

Discuss any issues with a professional (contractor, structural engineer, etc) to gauge their opinion. 

How to Maintain My Soils and Prevent Damage?

To limit the impacts of expansive soils, we recommend the following:

1.    Ensure proper drainage away
from foundations;

2. Utilizing gutter/downspout systems;

3. Maintain even landscape irrigation around buildings. 

 

 

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