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What Is a Wood Foundation? Everything You Need to Know About This Uncommon Foundation Style
Wood foundations can be great options in remote areas and cold climates
Photo: gmnicholas / iStock / Getty Images
Photo: gmnicholas / iStock / Getty Images
Highlights
Wood foundations are great for remote locations where concrete delivery isn’t possible.
They can include insulation, making them a decent option in cold climates.
They’re more expensive than concrete foundations.
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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?
Photo: DmitryPK / iStock / Getty Images Plus
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.
| Pros | Cons |
|---|---|
| Easier to finish than concrete basements | More likely to rot than concrete foundations |
| Easy access makes utility repairs straightforward | Less supportive than concrete |
| Make insulated walls possible for boosted energy efficiency | Much shorter lifespan than concrete |
| No issues with foundation wall cracks | More expensive to repair than concrete |
| Provide additional storage or potential living space beneath your home | More prone to insect infestation than concrete |
| Suitable for remote areas where concrete delivery isn’t possible | Durability isn’t well understood yet |
| Wood is a renewable building material, while concrete is not | Pressure-treated lumber contains potentially harmful chemicals, like chromated copper arsenate (CCA) |
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.
| Wood Foundation | Concrete Foundation |
|---|---|
| Can include insulation for energy efficiency | Can be insulated, but not as well |
| First used in the 1960s | Used reliably for thousands of years |
| Ideal in areas where concrete delivery isn’t possible, including remote build sites | Ideal in most locations, except remote build sites |
| Lightweight | Heavy but more durable |
| Options for crawl space and basement styles | Options for slab, crawl space, and basement styles |
| Prone to pest infestation | Sometimes prone to pest infestation |
| Prone to rotting | Resistant to rotting |
| Very expensive to install | Can be quite affordable |
| Very expensive to repair | Repairs are more often affordable |
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.
Frequently Asked Questions
Since wood foundations only became popular in the 1960s, home builders and engineers are unsure of how long wood foundations will last, although 60 to 100 years are common estimates. Most wood foundations in the U.S. are no more than 40 to 50 years old, and while some have already met the end of their lives, others that were meticulously maintained are still standing strong. Although the longevity of a wood foundation is unknown, concrete is still considered a more durable material for home foundations.
Wood foundations are most prevalent in remote areas where concrete delivery isn’t an option or would be prohibitively expensive. Wood foundations were first constructed in the 1960s, so some homes from around that time may have a wood foundation if the builder was testing out the new foundation technology at the time. In most cases, though, wood foundations are a sign of limited access to the build site.
Generally speaking, concrete is a more affordable material for home foundations, but wood can end up being more affordable—or the only option—for remote build sites where concrete delivery can get unusually expensive or unrealistic. So, while wood foundations cost more in most cases, they can end up being the more affordable option for homes in remote areas.
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