Pile foundations are used to support buildings on weak soils that cannot withstand structural loads. Piles transfer loads from the building through the weak soil to a stronger soil layer below. Piles can be made of timber, concrete, steel, or composites. They function by transmitting foundation loads to solid ground while resisting vertical, lateral, and uplift forces. Common pile types include end bearing piles that extend to bedrock and friction piles that transfer load through soil friction along their length.