How a house is built
What the house sits on
Slab, crawl space, basement, and piers solve different ground, frost, and access problems. This house is drawn as a slab-level pad.
Arrow keys turn the house. Plus and minus, or the zoom buttons, change the zoom. A horizontal drag turns it after you tap the drawing. Reset view returns to the step camera.
The drawing needs WebGL. The notes on the page still stand.
A slab on grade pours the floor on a prepared base, with a thickened edge or a stem wall and footing. A crawl space lifts the floor on short walls so someone can reach pipes and ducts. A basement is that wall, tall enough to be a room, and it has to resist soil and water. Piers and grade beams carry the house on points when the soil near the surface is poor or the site is steep.
The choice follows the soil, the slope, frost depth, and whether anyone needs to get under the floor. This sketch is a low pad with the main floor at grade. It is not a soils recommendation and not a basement.