Expansive soil is dirt that is made fine particles that was suspended in water and then settled to the bottom. When you walk in it when wet, you grow an inch when it sticks to your shoes. When it drys, it developes cracks big enough to stick you hand in.
Here in Southern California there are pockets of it that cracks driveways and slabs. I hear that in Texas the clay soil is so bad that the ground expands a foot up and down over the seasons. Is that true, how do you deal with it? Do others areas have the same problem?
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Since you didn't mention in your post what you intentions were regarding the expansive soil, I can only tell you that here on the central coast of Ca, some soils are very expansive, but not to the degree you mentioned hearing about in Texas. My first house was on adobe which caused the back yard to change elevation about 3 inches from wet to the dry season. The city required that the contractor post-tension the slab on four foot centers with 5/8 cable. We sold the house after 18 years and the slab had only minor hair line cracks in it. Without the tension, the slab would have broken into many large pieces.
There is no intentions, I always like to hear about other areas and how they deal with things. Californians always think the grass is greener somewhere else.
Lots of expansive soils along the front range in Colorado.
Colorado Geological Survey, Department of Natural Resources, publishes a booklet that covers the topic pretty well: A Guide to Swelling Soils for Colorado Homebuyers and Homeowners Special Publication #43. Call them at 303-866-2611 if you want to read up.Any jackass can kick down a barn, but it takes a carpenter to build one.
One approach that I've seen used in Colorado (it's probably in the book that Hasbeen references) is to rest the footings on caissons, concrete posts that extend to a depth where the soil presumably never dries out.
I've heard of people in Texas running the sprinklers year round to make sure the soil never dries out and shrinks.
I've also seen references to raft foundations, very thick, rigid concrete slabs that don't bend when faced with differential expansion. The house may tip, but the floor will stay flat. This may have been intended for frost heaves instead of clay, but the principle seems applicable.