A foundation system is the part of a structure that transfers its loads into the ground, through elements sized and selected for the soil and rock beneath the site.
Foundations fall into two broad families. Shallow foundations, such as spread footings and mat slabs, bear on soil near the surface. Deep foundations, such as driven piles, drilled shafts and auger-cast piles, carry load down to stronger layers. A geotechnical investigation sets the allowable bearing pressures and recommends the system.
Parking-specific considerations
- Column loads. Long-span parking structures concentrate load in fewer, heavier columns, which affects footing size or pile counts.
- Below-grade parking. Basement garages add excavation, shoring, waterproofing and, where the water table is high, uplift from groundwater.
- Future capacity. If a garage may add levels or be converted to another use, the foundations must be designed for those loads from the start; adding capacity later is costly.
The Parkonomics view
The foundation is where future-proofing is cheapest and most often skipped. A modest increase in foundation capacity at construction can preserve the option to add floors or convert the structure decades later. Decide what the building might become before the footings are designed.
Related terms: Adaptive Reuse, Service Load, Ultimate Load, Short Span
Further reading: Rethinking Future Proofing, Part 1: Planning and Design