Concrete Uniform Thickness Slabs are sometimes specified for use on expansive soil. They are usually very thick and require more reinforcement and concrete than an equivalent Wafflemat foundation.
When expansive soil expands under a Uniform Thickness Slab, it has nowhere to go, so the foundation is pushed upward with the full force of the expanding soil. Incorporating Wafflemat in the design of a Uniform Thickness Slab reduces concrete volume and the amount of required reinforcement, yet it still provides a foundation with the required rigidity to resist the uplifting forces. Wafflemat also absorbs some of the volume change of the expansive soil and thereby minimizes the amount of uplift force on the foundation.
Wafflemat foundations more efficiently use concrete and reinforcement materials. The use of non-expansive fill is usually not required with Wafflemat.
Uniform Thickness Slab:
Uniform Thickness Slab with Wafflemat:
What happens when you use Wafflemat with Uniform Thickness Slab?
- Wafflemat absorbs some of the volume change of expansive soil, thereby reducing uplift forces.
- Wafflemat makes more efficient use of concrete and reinforcement materials.
- Non-expansive fill is usually not required.
And without Wafflemat?
- Expansive soil is in contact with the entire foundation, and pushes the foundation slab upward with its full force.
- More concrete and reinforcement materials are required.
- Non-expansive fill is used to attempt to reduce uplift forces of expansive soil