Sometimes, expanded polystyrene blocks are used instead of plastic forms, to prevent creating an air space under the slab.
The monolithic pour creates concrete beams running throughout the footprint and perimeter of the foundation, with voids between, in one operation.
The waffle slab foundation is very stiff, with strength to resist differential swelling resulting from landscaping practices, surface drainage, or flooding from any source.
[citation needed] The higher contact pressures along the base of the ribs and the voids or low pressure areas in the system limit deformations of soil due to moisture variation to the void spaces, reducing the impact of the soil's volume change on the on-grade mat slabs.
Because a waffle slab uses less raw materials (cement, iron, fuel, water, aggregate, and sand) than traditional slab-on-grade foundations, the system is also more environmentally sustainable.