You know what they say; a house is only as good as its foundation.
Though it’s usually not the first thing you look at when buying a house, the foundation is one of the core aspects to consider. It’s the lowest load-bearing point in the entire house, which means it’s responsible for supporting the walls and pretty much everything between them.
Common house foundation types include crawl spaces and slabs. The main differences are that slab foundations are faster to build and more affordable, but crawl spaces offer a space for utilities, which is pretty handy.
Here’s an overview of crawl space vs. slab foundations to help you make the right choice.
A slab foundation is a huge concrete base that sits underneath your house’s walls. The concrete is often 4–8 inches deep and reinforced with steel bars and footings. It’s also usually placed over a layer of crushed gravel for drainage purposes.
Nowadays, most slab foundations get poured as a single piece, which is otherwise called a monolithic slab. Monolithic slabs don’t have any seams, which makes them sturdy. On top of that, they’re pretty fast to construct, which is the number one reason they’re so popular.
However, monolithic slabs are also prone to cracking over time, especially when they’re not laid on level ground.
Here’s a roundup of the pros and cons of slab foundations:
- They’re pretty fast to construct because they get poured as a single piece
- They’re affordable compared to other foundation types
- They don’t require a lot of maintenance
- They’re not sensitive to moisture-related problems
- Slab foundations are prone to cracking if they’re not on level ground
- They can get damaged easily in frosty areas
- They’re pretty hard to remodel once they’re set
Crawl space foundations are elevated above the ground using exterior walls that are often 1–2 feet long, which means they provide an open space underneath the houses. These spaces are often used for cables, wiring, and plumbing pipes.
They’re pretty handy because they act as a buffer between the house and the ground, but they also take a long time to construct because they require support walls. On top of that, they need a lot of maintenance over time to make sure they stay dry and ventilated.
These open spaces tend to harbor moisture, which can lead to wood rot in the long run if you don’t take care of the issue.
Here are their pros and cons:
- They’re a good solution for sloped building grounds
- They’re sturdier and more durable than slab foundations
- They’re easy to remodel and rebuild
- They provide an open space for wiring and plumbing
- They’re less prone to soil shifting
- They require a lot of maintenance
- They’re not resistant to pest infestations
- They cost a lot and take a long time to build
Now that you know a brief about each foundation type, here’s an overview of their main differences.
Cost is a major deciding factor for most people when deciding to buy a house or build it. Between slab foundations and crawl spaces, it’s not hard to determine which one is more suited to your budget. Slab foundations are 30% more affordable than crawl spaces, give or take.
A slab of concrete will cost you around $7000–$15,000, depending on the house’s size and floor plan. Meanwhile, a crawl space will cost anywhere from $15,000 to $25,000, and maybe even more if the house is built on a huge ground.
Not all people are lucky enough to have a choice because not all areas are suitable for slab foundations. But if you do, you know what to choose if you want to save money.
A slab foundation isn’t only more cost-efficient at the time of building it, but it’s also more affordable in the long run because it doesn’t require much maintenance. There’s no open space, so there’s not much to maintain.
On the other hand, crawl spaces leave open-air space underneath houses, so they need frequent maintenance to make sure the pipes, ductwork, and wires running through are alright.
It’s worth noting, though, that crawl spaces are easier to access when something goes wrong. All you’ll have to do is check the open space to see what’s wrong. Meanwhile, with a slab foundation, you’ll have to break it open if you need to replace a pipe or do a similar task.
If you’re constantly looking up upgrades for your house, you’ll need to have a foundation that’s easy to remodel. Crawl spaces are a good fit for that. Whenever you want a change of scenery, you can remodel the house and change the crawl space accordingly,
Even better, if you have enough space, you can turn your crawl space into a basement to store your belongings.
On the other hand, slab foundations are permanent. Once they’re poured, it’ll be near impossible to remodel them, so if you fear that kind of commitment, you’ll be better off with a crawl space.
You may have read somewhere that slab foundations are resistant to pest infestations, unlike crawl spaces. However, that’s not true.
Both foundation types are prone to infestations, but crawl spaces are more at risk. They attract mice, rats, termites, and all kinds of pests and animals that can nest and breed underneath the house. Meanwhile, slab foundations mostly only attract termites, but that doesn’t mean they’re safe.
Slab foundations are actually at a high risk of getting a termite infestation because they’re closer to the soil, but they can always be treated with a termiticide treatment.
Energy efficiency isn’t one of crawl spaces’ strong suits.
A crawl space makes it harder to heat or cool your house. It’ll also need insulation from the outside air to keep the moisture out.
Most people need to have a conditioning system for their crawl spaces, or at the very least, a dehumidifier to deal with the humid air that gets sucked up to the floors. Add this to the initial cost of constructing a crawl space, and you’ll find yourself paying a lot to maintain it.
On the other hand, slab foundations aren’t prone to moisture accumulation, so they don’t need any special preparations to deal with humidity. All in all, they’re more energy efficient.
The question of whether crawl spaces are better than slabs depends on many factors, including the weather in your area and the leveling of your ground.
Here are different conditions to consider and which foundation type is better for each condition.
A crawl space is the obvious better foundation option for sloped ground.
If you attempt to construct a slab foundation on sloped ground, you’ll have to do plenty of digging to level the high side with the low side. Plus, the foundation will be at risk of getting cracked over time.
Meanwhile, you won’t need a lot of digging to build a crawl space because you’ll only have to make space for the walls.
If you live somewhere with a lot of rain throughout the year, a slab foundation is the right way to go. Crawl spaces are prone to moisture-related problems.
If it rains all the time, the space will likely get soggy and moldy, which may lead to wood rot over the years. Meanwhile, slab foundations are basically waterproof, and they’re often supported by polyethylene sheeting to repel the water and keep the concrete from absorbing it.
A crawl space is the better option for areas with a deep frost line.
When the ground beneath a slab foundation freezes, it expands and may cause the foundation to crack or, at the very least, shift.
Most slab foundations have footings around 24 inches beneath ground level, which is fine for areas that don’t form frost deep into the ground.
However, in some states, the frost can be as deep as 30 inches or more beneath ground level, exceeding the slab’s endurance. In that case, a crawl space is the better option.
The choice between a crawl space and a slab foundation boils down to your preferences and the area you’re living in.
Crawl spaces are better for frosty areas and sloped grounds, but they’re costly and require plenty of maintenance. At the same time, they’re not energy-efficient, so you’ll have to invest in a conditioning system to keep the humid air out.
Meanwhile, slab foundations are more affordable and don’t need much maintenance, and they’re better for wet climates because they don’t harbor moisture. Their major downside is that they can’t be remodeled, so they’re not suitable for people who want to frequently upgrade their houses.
I have a bachelor’s degree in Computer Information Systems and over 10 years of experience working in IT. As a homeowner, I love working on projects around the house, and as a father, I love investigating various ways to keep my family safe (whether or not this involves tech). I’ve also played guitar for almost 20 years and love writing music, although it’s hard to find the time these days.