Home Creations believes in building structurally sound, quality homes. That is why we believe one of the most important things to building a home starts with the foundation, which supports the structure of the home. Foundations are made of concrete and steel and are supported by soil. And as we all know, clay makes up most of Oklahoma’s soil.
Causes of cracking to the foundation:
1. Seasonal temperature
a. Changes in temperature and humidity can cause expansion and contraction of the foundation. In fact, about a quarter-inch of expansion and/or contraction is typical for houses in in Oklahoma.
2. Drying Shrinkage
a. This can be greater than seasonal variations and usually equals to 3/16 of an inch.
3. Freezing and Thawing
a. This can cause spalling to the foundation.
4. Chemical Changes
a. Chemical changes can range from: moisture expansion, sulfate attack, corrosion of steel, carbonation or alkali silica reactivity.
a. Overloading the foundation can cause the structure to become stressed.
a. Vibration can cause existing cracks to open wider.
The foundation must be able to withstand ground movement and limit distortion to tolerable levels in order to satisfactorily perform.
Foundation movement can be caused by:
1. Shrinkage and/or swelling
2. Compression of filled ground
3. Nearby construction
4. Compression of a soft layer in the ground
6. Soil softening
7. Variations in groundwater level
8. Collapse of mine workings
9. Frost heave
10. Chemical attack
As mentioned before, Oklahoma primarily has clay soil which can cause shrinkage and swelling to foundations. Why is this? Clay is made up of platelets. Changes in moisture causes them to absorb water directly into their crystal structure. Additional water causes them to swell, whereas removing water causes them to shrink. There is only two ways of reducing water in clay; these are: increasing the load of the soil and evaporation.
How do we build a good foundation?
First, we have to know our soil properties; which is clay. Secondly, we have to provide continuity between the slab and the foundation perimeter. We have found the perfect practice for this; which we call Enhanced Modified Slab on Grade. A modified slab on grade foundation is where the concrete slab if formed from a mold set into the ground. The concrete is then placed into the mold, which leaves no space between the ground and the structure.
Source: Dr. Chris Ranseyer, Ph.D., P.E., FACI. School of Civil Engineering and Environmental Science. The University of Oklahoma.