Pier and Beam: An Alternative to Slab Foundation
DURATION 5 min read
Houston residents have been dealing with flooding issues since the city’s founding 180 years ago. According to the Weather Channel, the Bayou City experiences an average of five days of flooding every year, making the greater Houston area the flood capital of the nation. So naturally, developers and homeowners are seeking solutions to reduce this risk.
One solution that has been around for a while is the use of a pier and beam foundation as an alternative to standard slab on grade foundation. This alternative is not a new concept and has been used in single-family and commercial structures in the Houston area throughout the city’s history. Take a trip through Houston’s historic Heights neighborhood and you will see many homes and structures with this type of foundation.
What is a Pier and Beam Foundation?
These days, pier and beam foundation is commonly found in older homes, but due to recent flood damage caused several significant rainfall events and recent changes to floodplain regulations by local regulating authorities, more home builders are converting to pier and beam to mitigate the chances of flood damage.
A pier and beam foundation is constructed with three primary elements: concrete footing, piers and support beams. First, concrete footings are buried eight or more feet to anchor the structure and prevent shifting. Piers, which are typically concrete, are then attached to the footing. Lastly, support beams are placed along the piers to connect the floor joists beneath the flooring.
A pier and beam foundation allows the home to sit 20 plus inches off the ground, creating a crawlspace that can be accessed from the home’s exterior. This crawlspace allows water to flow under the structure, rather than around a concrete slab in the event of a flood. This method helps developers comply with zero net fill regulations by raising the finished flood of the structure without adding mounds of dirt or a raised concrete slab that requires compensating excavation and storage volume.
Do Pier and Beam Foundations Work?
The Federal Emergency Management Agency (FEMA) conducted a loss avoidance study in southern Louisiana following Hurricane Isaac. The agency looked at 23 homes elevated with a pier and beam structure to see how they fared during the storm.
All 23 homes would have suffered more than two feet of flooding had they not been elevated. Had this damage occurred, it would have resulted in an estimated $2.24 million in repairs, which is 95 percent of the cost to elevate the structures. Though the losses avoided ratio was less than one (0.95), FEMA noted this study only represents one flood event over seven years, so the value of elevating a home is expected to pay for itself several times over the life of the structure.
In a separate FEMA loss avoidance study, FEMA evaluated pier and beam homes in Houston following Hurricane Harvey. The study found 1,618 elevated properties in our coastal area avoided more than $330 million in losses. These homes were elevated through $205 million worth of grants from FEMA, resulting in a return of investment of 161 percent.
FEMA concluded in both studies that elevating a home is an effective long-term solution to preventing flood damage.