"Slab foundations are common in areas of expansive soil, where a high clay content causes problems with settling and inadequate sub-surface drainage; they also became popular once technology evolved away from coal-fired furnaces to smaller electric and natural gas equipment. This essentially eliminated the need for a basement. And with the three car garages and walk-in-closets of today's housing, a musty, damp basement seems inadequate for storage of anything. Slabs also are easier, faster, and cheaper to build than full basements, requiring a day or less to form and prepare for concrete paving once excavation has been completed. Most affordable or first-time buyer homes are on slabs to lessen construction costs and thus the price of the finished house. They require less excavation and formwork and are often poured at the same time as their footings to create a monolithic structure.
Slab foundations rest on a bed of washed gravel to facilitate drainage under the slab and occasionally contain pipes or conduits for various utilities that will be set within the concrete. Measuring between six and eight inches thick, slabs also are often reinforced with rebar along the perimeter and a thick wire mesh across the breadth. All slabs are finished with control joints. These are man-made grooves along the surface of the slab to attract and regulate cracking that will occur during the curing process."