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What Is a Crawl Space? Types, Facts & FAQ

Crawl Space

When building a house, the first thing we do is lay out the foundation. And the stronger the foundation, the longer the house will last, not to mention have a higher resale value. So, what are our options here? The three most common house foundations in the US are concrete slabs, basements, and, of course, crawl spaces. They each have their pros and cons, and our focus today will be on crawl spaces.

We’ll talk about the very concept of crawl spaces, the various types, and what sets them apart from a basement. Next, we’ll cover every single pro and con in great detail so that you know exactly what to expect. Last but not least, we’ll answer the most frequently asked questions and compare crawl spaces to slabs. Here goes!

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How Does It Work?

So, what is a crawl space? And why is it called that? Well, a crawl space is an area that lies right below the first floor of a house—it’s the only thing between the house and the ground/soil. Crawl spaces aren’t at all fancy or comfortable. With an average height of 3–4 feet, they give you just enough room to climb underneath the house to access the pipes, electric lines, an HVAC unit, and everything else that’s usually hidden from the naked eye.

The low clearance (crawl spaces are rarely, if ever, taller than 6 feet) makes crawl spaces cheap and takes very little effort to build. However, depending on how small they are, it can be tiresome to stay down there for long hours. If you have a heating, electricity, or plumbing expert over, they will have the necessary experience and training for that. But, again, for the average homeowners, crawl spaces aren’t at all cozy. They do protect the house from moisture/humidity by lifting it, though.

Crawl Space
Image Credit: grandbrothers, Shutterstock

What About Basements? How Are They Different?

The biggest difference between a crawl space and a basement is that the latter is a full-fledged, full-weight room. You can use a basement not only for running the communications in the house or storing food but also as a lounge room where you can relax, work out, or do whatever you please. In contrast to crawl spaces, basements can (and should) be heated. That means they’re habitable 360 days a year. It will take a bigger investment and more time to build one, however.

Basements usually come with a concrete foundation but there are no strict rules as to whether they have to be half-exposed or fully underground. Just like crawl spaces, basements are where all your plumbing and electricity lines will be. There is one big downside with basements, though: they’re not ventilated, which means you’ll have a hard time keeping moisture levels down. Basements are warm, well-lighted, and comfortable, yet hard to keep dry. So, consider buying a dehumidifier.

What Are the Different Types of a Crawl Space?

Alright, now that we’ve learned our way around the concept of a crawl space, let’s talk about the differences between ventilated and conditioned crawl spaces. Right now, crawl spaces make up roughly 15% of foundations in American homes, and they can either be sealed or ventilated. Here’s what they bring to the table:

Ventilated Crawl Spaces

As the name suggests, ventilated crawl spaces feature a number of air vents. You’ll find them “sitting” right at the top of the so-called foundation walls. For proper ventilation, contractors place them in specific spots so that the air can freely move underneath the house and prevent moisture buildup. With that said, in some cases (like if you live in a humid area) air vents are NOT recommended.

That’s because the air that flows from the outside can be moisturized and boost humidity levels instead of lowering them. And what about insulating a ventilated crawl space? It’s an option, yes, but does take time and effort. The easy solution is to just put an insulating product between the joists. But, treating HVAC parts, pipes, and wiring is usually quite challenging.

The fellow looking under the bed
Image Credit: WeAre, Shutterstock

Sealed/Conditioned Crawl Spaces

A reliable vapor barrier (plastic/foil sheet for damp-proofing) paired with insulated walls—that’s what sealed crawl spaces are all about. For proper conditioning, we recommend connecting the barrier to your home’s HVAC system. Do that and you won’t have to worry about heating the space between the joists or establishing any vents. A vapor barrier laid over the ground will keep moisture levels to a minimum. But without it, the crawl space will get even more humid.

Where Is It Used?

Crawl spaces are just that—tiny spaces where you can crawl to fix piping and wires, and check for moisture. In contrast to basements, crawl spaces are very short. If the house has footings to support its weight and there’s an empty area between the first floor and the ground, that area will be classified as a crawl space. So, where is it used? Crawl spaces are used for hiding HVAC system components, tubes, and electric lines as well as controlling humidity levels.

What Can You Store in a Crawl Space?

The list of stuff that one can put in a crawl space is pretty large. However, most of us only put things down there that we rarely use, including old clothes, toys, and electronic devices. As for food, crawl spaces are perfect for storing canned goods. The reason: they’re not “afraid” of rats, termites, or high humidity levels. Therefore, perishable foods should NEVER be put in a crawl space.

Oh, and do remember to always keep food in plastic bottles and containers as an extra layer of “defense” against critters and pests. Otherwise, it won’t last long. Speaking of protection, building a couple of shelves in the crawl space will serve as a great remedy against potential moisture damage.

Crawl Spaces
Image Credit: JPJPJP, Shutterstock

Advantages of a Crawl Space

  • Cheap compared to a basement. Crawl spaces won’t cost you a fortune: All you’ll need is a set of footings for the house, and that’s it! No soil, concrete, bricks, or wood is required to build a crawl space, and that’s its biggest pro, especially if you have a modest budget for the foundation.
  • Doesn’t take long to build. Even if you want to fully ventilate or seal the crawl space, it won’t take nearly as much time to build compared to a basement or even a concrete slab. Essentially, a crawl space is just a “vacant” area that you can use to run all the communications, store some food, and more.
  • Flexible and versatile. While crawl spaces aren’t as cozy as basements, they are still quite flexible. First, you’re not limited to a specific size (length). Second, you have a choice between ventilated and conditioned crawl spaces. And finally, if need be, you can turn it into a full-fledged basement.
  • Gives access to wires and pipes. Unlike with a concrete slab, with a crawl space, you do get access to hookups, plumbing, and wiring. That allows for keeping all the important systems in a house in working order. Don’t want to crawl underneath the house to check a faulty pipe or tube? No worries: a contractor can do that for you.
  • A great choice for a sloping site. Crawl spaces are the best pick if you’re building a house on a sloping site. On top of that, they easily handle dry and cold climates and won’t crack or deteriorate during a harsh winter.

Disadvantages of a Crawl Space

  • Weak against moisture. A ventilated crawl space in an older house is a humid disaster waiting to happen. If left untreated, over time, it will damage the very structure of the house by making it decay, rot, and cultivate mold growth. Pests will also be a problem. If you seal it with a barrier instead, all of that can be avoided, but humidity is still a problem with this type of foundation.
  • Poor resistance to tornadoes and earthquakes. When the house is sitting on top of a concrete slab or a basement, it is much stronger against natural hazards like earthquakes or storms. But if it’s a crawl space, the only things holding the house in place will be the walls and the footings.
  • Too small for comfort. We’ll say it again: it’s not at all fun to crawl underneath the house, especially if the crawl space is lower than 6 feet and you’ve got dirt and water down there. On the other hand, if you aren’t afraid to get your clothes dirty, this won’t be that big of a problem.

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FAQs: Crawl Space

How is a crawl space different from a slab?

Slabs are significantly cheaper than crawl spaces. But crawl spaces are better at handling cold and dry climates. Crawl spaces are the go-to choice for sloped lots, too. More importantly, with a crawl space, you’ll always have access to all the electrical lines and plumbing. If you go with a slab, it will all be out of your reach, as it’s nothing more than a thick piece of concrete. Slabs are easier to maintain, though, and more energy-efficient.

What’s the average size of a crawl space?

The largest crawl spaces reach 6 feet in height, with most hanging in the 3–4-feet range. That’s exactly why these areas are called that. They are big enough for an average-sized person to fit down there to fix ducts, cables, and whatnot, but nothing more.

How much does a crawl space inspection cost?

This greatly depends on two things: the size of the crawl space and how easy it is to get to it. The tougher the working conditions, the higher the price will be. On average, a thorough inspection costs $100–250. So, how often should you do this? Ideally, it’s recommended to call in an inspector every 12 months. They’ll check for signs of standing water, wood rot, and dirt.

Moisture accumulating around the ductwork, rodents, and insects will be reported as well. Along with paying an expert, make a habit of examining the crawl space manually once in 6–8 months. This way, you’ll always be on top of things and any potential issues will be much easier (and cheaper) to fix. Severe damages do, indeed, cost a lot to fix ($5,000–6,000) and take time. Cleaning a crawl space, in turn, will set you back $500–3,500.

Low Crawl Space
Image Credit: JPJPJP, Shutterstock

Can you turn a crawl space into a basement?

The answer is yes, this is very much possible. In fact, people have been converting crawl spaces into basements for over 6 decades now. This isn’t a simple job, though, and only a team of experienced pros can handle it. First, they’ll have to jack the entire house up and hold it steady with support beams. The next step would be to excavate the soil to the right depth. After that, contractors will pour in concrete for the foundation and only then bring the house back down.

When to Go with a Crawl Space When Not to Go with a Crawl Space
You’re on a somewhat limited budget You live in a hot and humid region
You only need space for the pipes/ducts You don’t want to fight mold and pests
There’s no time to build a basement Natural disasters are common in your area
The house is to be built on a slope An extra room for leisure is a priority

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Crawl spaces aren’t as cheap as concrete slabs or as spacious as basements. But, they do have a long list of pros that strongly outweigh the cons. If you’re looking for a house foundation that’s cheaper than a basement yet gives quick and easy access to pipes, ducts, electric lines, and wires, a crawl space will be the optimal choice.

True, it’s not that easy to, well, crawl down there, and it’s somewhat weak against natural disasters. However, as the golden middle between the other two options, a crawl space is well worth your attention. Just make sure to consider all the advantages and disadvantages before you start building a house so that you’re not disappointed later on!

Featured Image Credit: JPJPJP, Shutterstock


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