Slab on Grade
A slab on grade is a foundation type where the concrete floor slab sits directly on top of compacted soil and rigid sub-slab insulation, with no basement or crawl space underneath. Slabs on grade are simpler and cheaper than full basements, common in warm climates and increasingly common in cold-climate Passive House builds (paired with frost-protected shallow foundation details). The dominant heat-loss path is the slab edge, which is why F-factor and edge insulation matter so much.