This foundation style raises some questions and we’re here to answer them
Pier and beam, crawl spaces, and raised slabs are all considered raised foundation styles.
Raised foundations are best for areas where water intrusion is a concern.
They are a suitable option for most sloped plots of land.
When you’re building a home, deciding on the right type of foundation is one of the most important choices you’ll make. Homes in areas prone to flooding or on uneven ground can benefit from a raised foundation, which keeps the ground floor elevated so it’s not in direct contact with the soil.
Learn more about the different types of raised foundations, the pros and cons of this foundation style, and how to decide if a raised foundation is the right choice for your home.
A raised foundation is one where the main floor of a home sits aboveground level, usually between 2 and 4 feet higher than the surface of the earth. The foundation often includes piles or foundational supports that stretch down into the ground to find support from soil that won’t shift or expand in response to changes in moisture and temperature.
Different types of raised foundations are suitable for different home styles, environmental conditions, and expected longevity. Knowing the specifics of raised foundation styles can help you choose the right one for your home.
Pier and beam foundations consist of long concrete piers that reach a few feet below the ground and extend above the surface. Home builders usually anchor vertical wooden supports—called “beams”—to the top of the pile. Those beams directly support the flooring system of the structure.
Pier and beam foundations create what is sometimes referred to as a crawl space, although it’s different from a crawl space foundation. The space is usually unfinished, so the floor of the area is dirt. Some homeowners leave the sides of this space open, while others wall off the area with plywood, lattice, or another building material.
Crawl space foundations create a similar underhome area to a pier and beam foundation, but the walls are concrete blocks, so they provide more support for the structure above, and they also serve as a means of protection for the area from water, insects, and rodents. Crawl space floors can be dirt, but home builders more often pour a concrete slab to serve as the floor.
Throughout the underhome area in a proper crawl space foundation, you’ll see supports much like you would under a pier and beam foundation. However, rather than sinking deep into the ground beneath the floor of the area, they sit on the slab or shallow footings.
Raised slab foundations consist of footings that sink beneath the ground and concrete walls around the perimeter of the home’s footprint sitting on top of the footings. The flooring system of the home rests on the concrete block walls.
The difference between a raised slab foundation and a crawl space foundation is that there is no underhome space created by a raised slab foundation. Instead, the builder will fill that space with compacted soil and gravel to wick water away from the slab above. The homebuilder will construct the concrete block walls above the surface of the earth, fill the space created with soil and gravel, and then pour the slab on top.
Like any other foundation style, raised foundations have some upsides and drawbacks to consider.
Because raised foundations are elevated off the ground, the risk of water damage from flooding, heavy rain, and excessive groundwater is significantly reduced. With a raised foundation, water flows underneath the house, not into it.
Pier and beam and crawl space foundations allow easy access to utilities via the crawl space, making repairs easier than they are with other foundation styles.
Foundations that create a full basement rather than a crawl space can cost significantly more than raised foundations. Raised foundations average $6 to $18 per square foot, while basement foundations can cost $20 to $27 per square foot.
Raised foundations keep flooding and groundwater out of your home, but crawl spaces are prone to moisture accumulation, which can lead to mold and mildew growth as well as structural damage. Ensure your crawl space is properly ventilated and waterproofed to avoid moisture issues.
The area under a raised foundation is an inviting place for insects, rodents, and other critters to make a home. Once they’ve moved in, they can access the rest of your home and cause property damage and health issues.
A raised foundation is more budget-friendly than a basement foundation, but it has a higher price tag than a slab. Having your home elevated off the ground will cost you more than a basic slab-on-grade foundation.
Compared to a basement, a crawl space doesn’t offer much in the way of storage space. They’re often too hard to access and not large enough to serve as a usable storage area.
On average, a raised foundation costs between $8,000 and $24,000, or an average of $4 to $18 per square foot. Raised foundations require less excavation than basement foundations and can often be constructed faster, using fewer materials.
Although raised foundations are ideal in certain situations, other foundation styles also have their own upsides in other locations and climates. Some homeowners also just prefer different foundation styles for their utility or appearance.
Monolithic slabs and slab-on-grade foundations are the most affordable foundation options and take the least amount of time to build. They require minimal excavation and ground preparation, but they can’t be used for some kinds of homes and in some areas. Slab foundations aren’t ideal for areas prone to flooding or with a deep frost line.
Basement foundations offer additional living or storage space below the home and are a good choice for areas with a deep frost line. Compared to other foundation styles, they add the most value to a home, but they come with a hefty price tag to construct. Like raised foundations, basement foundations are prone to moisture accumulation and pest activity.
Interestingly, although basement foundations also leave the first floor elevated a foot or two off the ground, they aren’t usually considered raised foundations. It’s unclear exactly why this is, especially since unfinished basements often provide the same benefits as crawl spaces in terms of avoiding water damage. It’s possible that the fact that finished basements would still leave living areas exposed to water damage from intrusion is the reason for its exclusion.
Raised foundations have their fair share of issues, but they are still a popular foundation option in areas that experience flooding and heavy rainfall or snowmelt. The primary goal of a raised foundation is to protect the main floor from water intrusion and water damage, and lifting the floor up off the ground is one of the best ways to accomplish this.
Some types of raised foundations—particularly pier and beam and crawl space foundations—are also good options where highly expansive clay soil can cause problems for concrete slabs. The footings under a raised foundation usually reach down far enough where runoff soaking under the concrete and changing the soil volume at that level isn’t as much of a concern.
Finally, raised foundations other than raised slab foundations are great options for homes built on sloped plots or uneven ground. The supports beneath pier and beam and crawl space foundations sink into the ground and provide level support where slabs would generally be out of the question.
If you’re still not sure whether a raised foundation is right for your home, call a foundation contractor near you. They should be able to advise you on the best foundation option for you.
In areas that are prone to flooding, a raised foundation is significantly better than a slab, as the added space under your home leaves room for standing water that won’t reach your main floor. Raised foundations are more expensive to build than slabs and often leave underhome areas that are prone to pest infestation, moisture issues, and mold growth, so they aren’t universally better.
Raised foundations can last between 75 and 100 years, but some can last much longer. The life span depends on the type of raised foundation and the amount of water and soil movement it experiences. On average, pier and beam foundations will last for around 75 years, raised slabs will last for around 90 to 100 years, and crawl space foundations typically last for a little over 100 years.
The primary reason home builders choose crawl space and pier and beam foundations is to get the footings below the frost line to avoid movement in the winter. However, raised foundations—including raised slab foundations—are also popular in areas where flooding is common and on plots of land where the land is uneven or sloped.
