Building foundations transfer vertical and horizontal loads across a large enough area that prevents structural damage and failure. While slab-on-grade foundations lack basements and rest on reinforced concrete pads, pier-and-beam homes rest above crawl spaces consisting of concrete-filled cylinders or pad footings. To support the home’s structure, short masonry foundation walls or concrete beams work with the footings and piers minimizing the foundation shifting.
Some pier and beam homes feature concrete beam walls supporting the house’s exterior walls. These structural members are reinforced with steel, which strengthen the foundation and increases its shear capacity for supporting live loads. The reinforced steel can continue supporting the structure, even if the concrete itself bends or cracks. Working in concert with the piers, concrete beams help transfer the loads down the foundation and through the footings. This is particularly useful in pier-and-beam foundations built on expansive or unstable soils, since the concrete beams redirect the load to the piers rather than the soils below.
Masonry Foundation Walls
Foundation masonry walls made of brick or concrete blocks are also used in pier-and-beam homes. Similar to concrete beams, masonry foundation walls support both vertical gravity loads and resist horizontal shifting from seismic activity. Unlike homes with basements, no excavation is needed building masonry walls for pier-and-beam foundations. The piers, which should be at least 12 inches above the ground line, support the floor beams above. Masonry foundation walls are susceptible to moisture damage and thermal transfer, although insulation can protect against cracking and other structural damage.
Piers and Footings
In addition, foundation walls in pier-and-beam homes work simultaneously with footings and piers preventing damage to the raised-floor structure. The footings help transfer the loads across the foundation, and are sized based on soil condition and the building’s weight. Piers rest on top of the footing pads, which support the beams and floor joists underneath the house. Similar to foundation walls, piers are constructed from brick, concrete block, precast concrete or brick veneer. Typical footing types that support foundation walls include spot footings, continuous spread footings and grade beam footings.
The foundation walls in pier-and-beam homes have benefits compared with other foundations that use a cut-and-fill slab method. Pier-and-beam foundations disturb less soil and minimize foundation movement. Unlike slab-on-the-ground foundations, additional plumbing systems and appliances are accommodated in the crawl space beneath the raised floor. Pier-and-beam foundation systems do not require reinforced retaining walls for proper drainage. For residents living in coastal or flood-prone areas, pier-and-beam foundation walls are a cost-effective solution for meeting zone elevation requirements.
- Photo Credit Jupiterimages/Polka Dot/Getty Images