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What Is a Crawl Space? (101 Guide for Beginners)

What Is a Crawl Space? (101 Guide for Beginners)

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Building a new house can be exciting but also overwhelming. There are so many details included in the process, like the materials, colors, finishes, foundations, and so on.

When it comes to foundation types, there aren’t many choices. It’s either a basement, a concrete slab, a wood foundation, or a crawl space, but what is a crawl space?

A crawl space is a hollow area between the ground and the bottom of your house. It’s usually too narrow and only accessible through crawling, hence the name “crawl space.”

Keep scrolling for more info about crawl spaces and their advantages versus their disadvantages.

What Is a Crawl Space Foundation?

A crawl space foundation is a type of house foundation that’s more convenient for stable soils. It’s basically made of poured concrete footings and walls that help elevate the house from the ground by about 18 inches to 4 feet.

Crawl space’s function, among many things, is to provide access to the bottom of the house where all the electrical wiring, heating/cooling system, and plumbing is.

There are two types of crawl spaces that are built under a house: open crawl space (vented) and conditioned crawl space (unvented).

What Is an Open Crawl Space?

An open or vented crawl space, as the name suggests, has multiple air vents at the top of the foundation walls.

Typically, builders create a minimum of 1 sq ft vent per every 500 sq ft of crawl space area. Ideally, those vents are located across from each other for better airflow.

However, vented crawl spaces are no longer recommended. Aside from allowing pests to go inside and nest, vented crawl spaces are also prone to humidity and mold growth.

What Is a Conditioned Crawl Space?

Conditioned crawl spaces, unlike vented ones, are totally sealed. They are also known as encapsulated crawl spaces.

Conditioned crawl spaces are highly recommended as they keep your crawl space dry. Consequently, they prevent wood rot, pest infestation, and mold growth.

Typically, builders protect enclosed crawl spaces using insulation, vapor barriers, drainage systems, and sometimes a crawl space dehumidifier.

All this insulation doesn’t only help control the inside conditions of the house and save energy but also makes your conditioned crawl space work perfectly as a storage area.

What Are the Advantages and Disadvantages of a Crawl Space?

Though crawl spaces seem like the perfect solution for many problems, they do have some disadvantages.

Here are the advantages and disadvantages of having a crawl space:


Crawl spaces are ideal for sloped lots that have poor-draining soils, and they can be used as storage.

Other advantages of having a crawl space underneath your house include:

Construction Cost

Having a crawl space is much more affordable than having a basement. That’s because it can cost you between $8000 to $21,000 to build a crawl space for an average-sized house.

On the other hand, the price range for building a basement is anywhere between $75,000 and $150,000.


Compared with a slab foundation, crawl spaces provide easy access to the piping, wiring, and ductwork underneath the house, which in return facilitates maintenance and repair.

Energy Efficiency

Crawl spaces, when encapsulated, improve air quality and eliminate humidity. This makes the air circling inside your house dry and clean.

Consequently, your air conditioning unit functions with optimum energy, as it doesn’t have to fight off moisture.

This eventually leads to lower utility bills and increased energy efficiency.


When enclosed, crawl spaces regulate your home’s temperature, making the floors warmer and more comfortable to walk on, especially during cold months.

Similarly, conditioned crawl spaces prevent your house from getting too humid, especially during hot summer days.


Although the advantages of having a crawl space underneath your floors are a lot, there are also some disadvantages you should consider, which include:

Construction Time

This isn’t a big deal for some, but if you’re running short on time, you might want to take into consideration that crawl spaces take more time to build than slab foundations.

Additionally, because a crawl space raises your house’s level above ground, you’ll need to add stairs leading to the entrance.

Moisture Issues

Crawl spaces, if not properly insulated, can trap moisture, which leads to the growth of mold and fungi. Consequently, this would lower the air quality inside the house and lead to health issues.

That said, even if you installed insulation and vapor barriers, you should regularly check your crawl space for moisture to avoid some of these issues.

Impracticality in Cold Regions

In the northern U.S. states, crawl spaces aren’t that practical. That’s because they elevate the house above the ground.

Full basements, on the other hand, are needed in those areas to get the foundation of the house below the frost line. Consequently, this protects the piping from freezing in winter.

Other Disadvantages

A crawl space foundation, just like a slab foundation, provides little to no protection for the house against storms.

Additionally, they lower the resale value of your house, especially if the surrounding homes have full basements.

All in all, you should avoid open crawl spaces. Not only do they increase the moisture inside, but they also make the heating or cooling process more difficult and energy-consuming.

Do All Houses Have a Crawl Space?

No, not all houses have a crawl space. Some houses have basements, while others sit right on a concrete slab.

In fact, only a small percentage (15-20%) of homes in the U.S. have a crawl space. Though the percentage might seem insignificant, the number of houses isn’t that small.

More than 20 million houses in the U.S. have crawl spaces. Sadly, most of them are poorly built, which leads to the disadvantages that were previously mentioned.

Can You Get Sick From a Crawl Space?

Yes, as mentioned before, crawl spaces that weren’t properly insulated may get you sick and lead to some health issues.

That’s why you should regularly maintain your crawl space and check for any problems that might’ve occurred. Those problems include:

1 – Moisture

You shouldn’t worry much about moisture when your crawl space is insulated. However, if there’s any issue with insulation, damp air can escape into your crawl space.

Evaporating moisture can highly damage the insulation as well as the wooden ceiling of the crawl space, which leads to mold and mildew.

Eventually, this mold makes its way into your house’s floors and walls, which causes allergic symptoms, such as coughing, sneezing, itching, headache, wheezing, and so forth.

Unfortunately, repeated exposure to mold can cause even more severe allergic reactions. Not to mention that certain types of mold, such as Aspergillus and Stachybotrys, produce toxins.

2 – Radon

Radon is a dangerous natural gas that emits from the ground. It’s found in most soils, and it has no smell, nor can it be seen.

If leaked into your house, radon gas can lead to serious health issues. In fact, some studies have linked radon exposure to lung cancer.

More shockingly, according to the EPA, radon exposure is currently the second cause of lung cancer after smoking.

3 – Pests

Moisture in crawl spaces forms the perfect environment for insects and small animals to nest.

Additionally, crawl spaces provide those creatures with a safe, undisturbed home. They can house all kinds of spiders, rats, snakes, and termites.

Those creatures’ droppings, as well as urine, affect the air quality inside your house because of all the microorganisms they contain, which might lead to health complications.

Do Crawl Spaces Have Windows?

The majority of crawl spaces don’t have windows, but they can! That said, it’s better not to install windows (even the fixed type) in your crawl space, as this compromises its efficiency.

Vented crawl spaces, on the other hand, have small vents, which aren’t considered windows. Additionally, as previously mentioned, a vented crawl space isn’t the best choice.

That said, for accessibility, crawl spaces do need to have a door in case something goes wrong and the maintenance guy needs to take a look.

Final Thoughts

Whether you’re building a house or looking to purchase one, take the foundation into account. Crawl spaces aren’t for all houses, and they come with some disadvantages.

So, if you end up with a house that has a crawl space, just make sure it’s well insulated.


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