What Is a Wood Foundation? Everything You Need to Know About This Uncommon Foundation Style

When most people think about home foundations, they immediately think of concrete slabs and concrete block walls. Wood foundations made out of pressure-treated lumber are another option, and while their durability isn’t quite as trusted as that of concrete, there are certain situations where installing a wood foundation makes sense. In this guide, we’ll explain what a wood foundation is, how much one costs to install, the upsides and drawbacks of wood foundations, and more.

What Is a Wood Foundation?

A wood foundation—also called a permanent wood foundation or PWF for short—is a foundation for a home built entirely or mostly out of pressure-treated lumber as opposed to concrete. In most cases, a wood foundation will consist of a wooden foundation floor and framed-out foundation walls, but it’s also possible to pour a foundation slab to act as the foundation floor and then install pressure-treated lumber framed out to make foundation walls above that slab.

It’s worth mentioning that wood foundations almost always include an underhome area, like a crawl space or a basement. They’re most common in remote areas in colder climates, where the foundation needs to rest on soil below the frost line, which can be a few feet below the ground.

How Much Does a Wooden Foundation Cost to Install?

The average cost of a wood foundation is around $40,000 for a typical home with a 1,000-square-foot footprint. This is more expensive than you’d expect for a basement foundation of the same size made out of concrete. While concrete is a more affordable building material, it can be expensive or unrealistic to transport mixed concrete to remote sites, which is where wood foundations shine. For a remote site, a wood foundation could be less expensive than a concrete foundation, and it might very well be the only option.

With that being said, the cost of wood foundations can vary wildly depending on a few factors. Things like transporting pressure-treated lumber to the construction site and getting excavation equipment to the remote site can push your per-square-foot installation prices significantly higher than the average of $40.

Types of Wood Foundations

There are two main types of foundations that builders can construct out of wood:

Wood Crawl Space Foundations 

Contractors building wood crawl space foundations will excavate the earth to between 4 and 6 feet beneath the surface to install a short underhome area, referred to as a crawl space. These are less common than wood basement foundations because they likely won’t reach below the frost line in very cold climates, where wood foundations are the most prevalent. If they are a possibility, they will be more affordable than a full basement made out of wood. The underhome area can house utilities and serve as a place for storage.

Wood Basement Foundations

Wood basement foundations are more common, as they fare better in the colder climates where wood foundations are prevalent. They are more expensive than wood crawl spaces, though, as they require more building materials and more labor in the form of excavation and backfilling. Homeowners can sometimes opt to finish wood basements, which provides potential living space.

Pros and Cons of Wood Foundations

Wood foundations aren’t as common as concrete home foundations because they’re more expensive and likely won’t last quite as long. However, there are some significant upsides to using wood as a foundation material as well.

Common Problems With Wood Foundations

Wood foundations are great in certain situations, but there are some unique problems homeowners might face when opting for a foundation made out of pressure-treated lumber.

• Prone to moisture issues. Most foundation specialists take great care to waterproof foundations made out of wood and protect them from moisture, but the wood will inevitably come in contact with ground moisture. Even pressure-treated lumber will rot over time, which can leave you with expensive foundation repairs. Unfortunately, an increased risk of moisture problems also promotes pest infestation and mold growth, both of which are more common with wood foundations than with their concrete counterparts.

• Not as structurally sound as concrete. Wood is not as strong as concrete under load, so you can build significantly higher on a concrete foundation than you can on one made of wood. Even single-level homes will be more secure over a concrete foundation than a wood one, so you’re more likely to run into structural damage with a wood foundation, which can be very expensive to repair. You’ll likely need to look out for foundation problems more often with a wooden foundation.

• Inward bowing of foundation walls. Wood is flexible, which means it won’t stand up as well as concrete will to hydrostatic pressure, the inward pressure exerted on foundation walls by the surrounding soil when it expands in the presence of moisture. You’re more likely to see inward bowing on your wooden foundation walls, which can leave your upper floors without the support they need. We recommend hiring a foundation repair company near you as soon as you notice this type of issue to get it handled immediately and prevent serious structural damage.

Wood Foundation vs. Other Types of Foundations

Wood foundations are more of a specialty foundation built in remote areas where transporting concrete isn’t realistic, whereas concrete foundations are the norm throughout the U.S. Still, there are some applications where a wood foundation makes sense.

When Is a Wood Foundation Used?

Wood foundations are somewhat rare in the U.S., as the majority residential building includes access to roads that allow for concrete delivery. In remote areas, where concrete delivery isn’t possible or would be excessively expensive, contractors often opt for wood foundations.

Wood foundations are most common in colder climates, like in Alaska, especially where build sites are more likely to be remote. Wood foundations include framing for the basement walls, where builders can install batt insulation or foam insulation to help protect the interior from freezing temperatures, which is an additional perk of wood foundations in colder areas.