If you’re building a home or thinking about moving, you probably have a lot on your mind, and what kind of foundation you want your new home to have might not be near the top of your list. Many home buyers don’t realize the impact that the type of foundation can have on maintenance, but your experience may vary dramatically depending on whether you choose a house with a slab foundation or one with a crawl space foundation.
This article takes an in-depth look at concrete slabs vs. crawl spaces to help you choose which is the better option for you. Below you’ll find a discussion of the pros and cons of each type of foundation and a head-to-head comparison highlighting the most important differences between concrete slabs and crawl spaces.
Slab vs Crawl Space Comparison
Slabs and crawl spaces are the two most common foundation types, and each has benefits and drawbacks. The following table presents an overview of the similarities and differences between slabs and crawl spaces.
| Slab Foundation | Crawl Space Foundation |
| Easier to maintain | More involved maintenance |
| Less expensive per square foot | More expensive per square foot |
| Faster build time | Takes longer to construct |
| No space for utilities | Space for pipes and utilities |
| Harder to access when something needs maintenance | Easier access if something goes wrong |
Slabs and crawl spaces can both suffer from similar problems, like poor soil quality, drainage problems (explore ways of enhancing yard drainage) from improper landscaping, and shoddy workmanship during installation, making it important to find pros to consult about your land’s overall health before you choose what kind of foundation you want.
What is a Slab Foundation?
A slab foundation is a chunk of concrete that sits on the ground underneath your home. Slabs are usually four to eight inches thick with an average thickness of around six inches, although some can be up to a foot thick. Most slab foundations are constructed in a single pour, a technique that produces a monolithic slab without any seams.
Unlike basement foundations and crawl spaces, slabs don’t provide any room for storage or running utility lines, so pipes are often embedded directly in the concrete slab, which makes it significantly more difficult to replace them when they wear out.
On the other hand, not having open air beneath your house makes it harder for insects and other critters to find their way into your home. Slabs are also more resistant to water damage, and you don’t have to worry about mold or mildew the way you do with crawl spaces and basements.
Pros & Cons of a Slab Foundation
Slab foundations have several attractive features that make them a good choice for many homeowners. However, there are tradeoffs you need to be aware of before you commit to buying or building a home with a slab foundation.
Slabs are more affordable and faster to build than small spaces, which can be a big advantage if you’re considering new construction. They’re also pest and moisture-resistant and don’t need much maintenance overall.
The downside to concrete slabs is that they are easily damaged by shifting soil and tree roots, and working on them is more difficult due to how inaccessible they are. They’re also not the best choice in cold climates where the frost line isn’t very deep or for properties with graded lots.
Pros of Slab Foundation
- Cheap and fast to build
- Resistant to infestations from termites and other pests
- More energy efficient
- Low-maintenance
- Better in wet climates
Cons of Slab Foundation
- More susceptible to shifting soil
- Not suited for sloped properties
- Prone to damage from ice in cold climates
- Hard or impossible to remodel
What is a Crawl Space?
Crawl spaces have exterior foundation walls that raise a home one to two feet off the ground, providing an open-air space underneath. A crawl space foundation provides a convenient and safe place to run the home’s plumbing, wiring, and HVAC ductwork, giving it a significant advantage over a slab in this regard.
Pros & Cons of a Crawl Space
Crawl spaces offer a few important advantages over slabs. The biggest benefit to having a crawl space instead of a slab is the space it gives you to run your home’s utilities where they won’t be prone to freezing.
A crawl space is a perfect place to run wires and pipes, giving you easy access when you need it but otherwise keeping your utilities out of sight and out of the way. Crawl spaces don’t provide as much storage space as you get from a full basement, but they do offer some.
Another advantage is that crawl spaces are well-suited to uneven or sloped ground, making them the only option in some cases if your plot has a grade to it. Contractors can install crawl spaces on sloped land by embedding footers in the ground regardless of the angle. Building a slab foundation on an angled plot would require expensive excavation and leveling that would extend the project’s timeline.
Unfortunately, crawl spaces also have a few downsides compared to slabs. They’re more susceptible to moisture problems, often requiring vapor barriers and other waterproofing measures to keep them dry and free from mold. Crawl spaces are also great places for various critters like raccoons, squirrels, and rodents to cozy up.
Main Differences Between a Slab Foundation and Crawl Space
Here’s a quick look at the major differences between the two most common types of home foundations.
Affordability
If you’re considering new home construction and want to save a few thousand dollars, a concrete slab foundation is the way to go. Slab foundations cost between $7,000 and $12,000 on average, depending on where the house is being built and the details of the plot.
Crawl spaces are usually more expensive, costing anywhere from $10,000 up to $25,000. Unfortunately, some homes are not candidates for slab foundations, so you might not have a choice if the plot is not amenable to a slab. Your contractor will be able to advise you about the best option for your situation and help you pick the one that works best for you and your property.
Maintenance
Slab foundations are significantly easier to maintain since they don’t have open-air spaces, although that means they’re more difficult to work on when something goes wrong. Slab maintenance is more straightforward than crawl space maintenance, but slabs make it harder to work on your utilities.
Crawl spaces have enough space to run pipes, wires, and ductwork, making it easier to do maintenance when the need arises. By contrast, replacing old pipes or wiring requires breaking open a slab foundation, increasing the cost of repairing these elements of your home.
Energy Efficiency
Concrete slab foundations are more energy efficient than crawl spaces because they trap cold air in the winter and don’t harbor hot air in the summer. Crawl spaces can make your home harder to heat or cool, leading to increased energy bills.
Remodeling
Once a slab is installed, that’s it. Remodeling a slab is basically impossible, while a crawl space is more amenable to changes down the road. If you’re the kind of person who likes to change things up, slabs have an air of permanence about them that might make you uncomfortable.
Other Considerations
There are a few other considerations you need to make before you choose the kind of foundation you want.
New Construction vs Buying a New Home
If you’re having a new home built, you’ll have to decide which kind of foundation you want. It’s fairly common for your contractor to recommend one type of foundation over another, so it might be the case that your new construction’s region is better suited to one type of foundation over another.
If your plot has a significant grade, you’re probably better off choosing a crawl space, unless you don’t mind paying to have the ground leveled. If your property already has the ground level, you’ll have to choose based on different criteria.
On the other hand, if you’re shopping for a new home, buying one based primarily on the foundation doesn’t usually make sense. As long as the current foundation is in good health and doesn’t need major foundation repairs, you’re probably better off choosing a home based on other aspects, like its locations and features.
Homes that are already built often have the right kind of foundation for the area, although this isn’t always the case. Don’t be afraid to talk to an engineer about the kind of foundation if you have concerns, even if the foundation inspection doesn’t uncover any major issues.
Environmental Factors
Crawl spaces do better in colder climates — where utility lines run through a slab could easily freeze — and dry climates, while slabs are better in regions prone to wet weather. Crawl spaces are also better in areas with poor soil, like expansive clay, which can cause big problems for concrete slabs.
Natural disasters like earthquakes also tend to affect concrete slabs more severely than crawl spaces or basements, although all foundations can be damaged by earthquakes. If you live somewhere that is prone to earthquakes, a crawl space is probably the better option since it’s easier to access and repair than a slab, even though it may cost more to fix on average.
Conclusion
The right type of foundation for you depends on what you’re willing to spend, where you plan to live, and how much maintenance you’re willing to do. Crawl spaces are better than slopes in sloped lots and dry regions and they’re great for housing plumbing and wiring. However, they tend to cost more to build and trap moisture, leading to mold growth and rotting floor joists and subfloors if the problem goes unnoticed.
Conversely, slabs are great in wet weather, resistant to pests, and more affordable than crawl spaces, but they don’t do well in graded plots or areas with poor soil quality. If you’re unsure what kind of foundation is best for you, talk to a contractor who is familiar with the region you’re moving to. They’ll be able to help you decide what foundation makes the most sense for the area.
