Expansive Soils – A Potentially BIG Home Building Problem For Owner Builders

Most owner builders have never heard of “expansive soils” also known as “active soils” or “swelling soils.” Home building can be a challenge if these types of soils are present in the area where your new home is to be built – and especially if they are present on your lot.

So what do you need to know?

Owner builders need to know what expansive soils are, why they can create problems for a Home Building Fool like you, how to tell if you have any of these pesky soils on (or underlying) your lot, and what to do if it turns out that, in fact, you do.

Bentonite and other active or expansive soils are clay soils which are composed of very fine particles. The annoying property of these soils is that they easily absorb moisture (as in when it rains, or when you water your roses). When they absorb moisture, they “expand” รับสร้างบ้าน or swell up. “Big deal,” you say. What’s a little swelling compared to a big heavy house?

Well, the fact is that when these soils begin to swell, they exert tremendous pressures on anything that opposes them . . . like your house’s foundation for instance. Improperly constructed foundations, so exposed, can be lifted, cracked, and moved to such an extent that their load bearing job is compromised, and homes become almost unlivable.

Get the picture? This is nasty stuff!

A national warranty company insuring new homes in the Denver, Colorado area suffered claims losses in excess of one hundred million dollars during the housing boom of the early 1980’s. These losses were the result of damage resulting from Bentonite. And they could have been avoided – if the builders and building officials had understood how to design and build homes on such soils.

OK, now you know that expansive soils can be big trouble. So how do you as a budding owner builder avoid this problem?

First, avoid buying a home building lot that has expansive soils.

Soil Analysis
All construction projects should include a soil analysis to identify the types of soil present and determine their expansive properties. Local occurrences of expansive soils can be found in all of the soil categories shown on this map.

If you are in or near on of these areas, use extreme caution. Start with your local building department. The building official will know if there are expansive soils problems in your area. If the answer is yes, you will need to have your lot tested for expansive soils before you commit to the purchase.

These tests are done by taking samples at various places around the property and testing them in a laboratory to determine how much they expand when exposed to moisture.  Soils tests are done by engineers certified in soils and structural foundations. You will find such specialists in every area where there are soils problems.

If expansive soils such as Bentonite show up on the soils report, it is best to look for another lot. If you already own the lot, or if your heart is set on this particular lot, take heart. All is not lost. You can build your new home on a lot that has expansive soils if you have the footings and foundation properly designed.


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