A foundation is the structural element that transfers a building's weight to the ground and anchors it against settlement, frost heave, and lateral movement. Foundation types include spread footings with basement or crawlspace walls, slab-on-grade (concrete floor directly on prepared ground), and deep foundations using piles or caissons for poor soil conditions. Foundation design depends on soil conditions, building loads, frost depth, water table, and local building codes. Foundations must extend below the frost line to prevent heaving in cold climates. Waterproofing and drainage protect basements from moisture. Foundation problems—cracking, settling, water infiltration—are among the most serious and expensive building defects. Building permits require foundation plans, and inspections verify compliance before construction proceeds. For municipal facilities and infrastructure, foundation design considers long-term durability and the costs of repair or replacement.