Crawl Space Foundation: Is It Better Than A Slab Foundation?

Slab foundation vs crawlspace? Which is better?  It is the first thing you build so figuring it out is very important early on. Though there are other types of foundations, there are two primary concrete foundations. 

Slab Foundation vs. Crawl Space

There is a concrete slab foundation that consists of a single piece of concrete. Then there is a crawlspace foundation which consists of a crawl space on top of a concrete slab. But which one is better? 

What Is A Crawl Space Foundation?

A crawl space foundation is a foundation with concrete walls and a floor. The walls are at least 18 inches above ground level with access to this area after the house is set. The plumbing is usually installed in this area. 

Crawl space foundations will have a flat slab of concrete but are built up with concrete walls and sometimes wooden walls as well as footers. They have enough space for someone to crawl through to fix problems underneath. 

What Is A Slab Foundation?

Slab Foundation

This may be the most common type of foundation. A slab foundation is a thick concrete slab that is used as a solid foundation for a house. There isn’t any access underneath the slab and all plumbing is built inside it or on top of it.

Slab foundations need to be very level and at least six inches thick in the center and about two feet around the perimeter. Any thinner and the slab foundation won’t be stable so this isn’t a foundation to slack on. 

Things To Consider: Slab Foundation Vs Crawl Space

When deciding on whether to build a slab foundation or a crawl space foundation, there are a few things to consider. 


Wintertime can wreak havoc on your home. So it’s important to consider what winters are like when you are building. Slab foundations can crack if the temperatures are too cold, but then again, they also heat better. 

Either will work fine as long as winterizing is done and the proper concrete is poured in the correct way. Getting an experienced team with good reviews is a great way to make sure that winter is taken into account. 

Moisture Level

Moisture can also take its toll on foundations. So make sure your team considers this as well. A slab foundation can be slick when moisture seeps through but it is much better than a crawl space foundation for this.

That’s because, in humid areas, crawl space foundations allow mold and other bacteria to grow in the crawl space, not to mention, the mud. No one wants to crawl through the mud to check the plumbing. 


Although you can add heat lamps and such under crawl space foundations, it’s a better idea to opt for slab foundations if this is your biggest concern. That’s because the crawl space allows more air to pass through the bottom.

Air and moisture barriers can definitely help with this so if you do get a crawl space foundation, make sure that you install a moisture barrier. This can work as an air barrier in many cases as well.


Let’s face it, price is always a concern. Though crawlspace foundations are considered high-end, they are much more expensive than slab foundations. That’s because you are paying for the slab and then some.

Some contractors know this and won’t charge much extra for the crawlspace if they think it is important. So talk to them beforehand about the differences in prices. You may only have to pay for the extra materials. 


Crawlspaces need a lot more maintenance than slab foundations. But that’s because there is more to them. You will need to make sure everything is as it should be once every month or two in crawlspaces.

You can usually hire someone to do this that comes on a regular basis to check things. They usually charge discounts if you pay ahead of time for them to check-in.

Ground Levels 

Crawlspaces are better for uneven ground levels. That’s because they can be built on a hill whereas slab foundations can’t unless the hill is not very steep. For hills, it is best to build a crawlspace or basement. 

Building A Crawl Space Basement

Building a crawl space basement is not something just anyone can do. It’s very important that everything is structurally sound. After all, a crawl space foundation really is like a tiny basement and has similar purposes. 

The thing crawl space foundations are that they need to be done by a professional. They are more difficult to install than a slab foundation. So hire a professional to build a crawl space foundation or basement. 

How To Pour A Concrete Slab Foundation

How To Pour A Concrete Slab

Pouring a concrete slab is fairly easy. There are only a couple of things to make sure you do right after you get the right concrete mixture. That is to get a level slab and to make sure you know where to install plumbing. 

It’s also important to hire a professional if you want to pour a concrete slab for your foundation because it is the most important part of the structure. But here are the steps that a contractor might take.

Step 1: Laying The Outline

The first step is to outline your foundation. Mark each corner with stakes and then tie a string around each stake to create a visible outline. This will be the first step. Make sure that the stakes are symmetrical.

For example, you want your house to be square or rectangular. Or at least for the foundation to be. Otherwise, it won’t be stable and will be very difficult to build on. So ensure that each end is the same length. 

Step 2: Create A Trench

Now, dig a trench that is about 18” wide and at least 24″ deep. Check building codes in your area to ensure you get the right depth, but this is a good depth to start with. This trench will help you create footings. 

You need to build a temporary frame for the concrete foundation at this point that is just outside the trench. This will help you mold the concrete later on so make sure it is very straight and stable. 

Install rebar into the trench in a continuous line a few inches from the surface. You will need to create rebar tables every foot or so to keep the rebar from sinking down to the bottom of the trench.

Step 3: Create The Base

Create a layer of sand or gravel to cover the area where the concrete will go that will be about six inches deep. Level it out and cover it with a moisture barrier. This is where the concrete will be poured.

Create a rebar grid on top of this that is elevated to meet the other rebar. If you have all your footings in place then it is time to pour concrete. Remember, the center only needs to be a few inches but the perimeter needs to be a couple of feet. 

It’s important to check local building codes before construction begins. But if you hire a professional, they will do this for you.

Other Types Of Foundations

Other Types Of Foundations


There are many other types of foundations that don’t require concrete for the main slab. The other type of concrete foundation is a basement foundation which we are all fairly familiar with. Here are other options.

Wood Foundation

Wood foundations are very popular. Though most wood foundations will indeed have concrete footers, it is possible to make them without any. The footers can be dug deep to ensure they are solid even if they are made of wood.

Wood foundations are becoming a little outdated, however, as it has been discovered that those reinforced with concrete are much stronger. So even if you use a wood foundation, concrete footers are highly recommended. 

Pier And Beam Foundation 

A pier and beam foundation is a very strong foundation, for a time. The foundations have footers that look like table legs that are load-bearing, holding up the above beams. Pier and beam foundations are uncommon. 

Pier and beam foundations are very similar to crawlspace foundations because they have space underneath the foundation. But the support isn’t as strong and they aren’t built on a concrete slab, but rather the ground.

Brick Or CMU

Although CMUs are made of concrete, they aren’t poured concrete. They work more like bricks. Both options are quite strong with CMU being slightly stronger and longer-lasting. This type of foundation is built piece by piece.

A brick or CMU block foundation can be very, very strong if built correctly, but a mason is needed to oversee the operation. These can have crawlspace underneath or be built more like a concrete slab.


A stone foundation is probably the oldest stable foundation still in use today. It works just like a CMU foundation but it is made of stone. Sometimes the stones are cut to fit together but other times they are natural. 

Cob houses often incorporate stone into the foundation to elevate it and to help insulate the home. But even some modern, on-the-grid homes will have stone foundations for aesthetics and availability. 

Frequently Asked Questions (FAQ)FAQ

Is A Slab Foundation Or Crawl Space Better For Cold Climates?

A slab foundation works better for cold climates on most occasions because they are more energy-efficient. The space in the crawl space doesn’t do a good job of keeping your home warm in the winter without a lot of effort.

Is A Slab Foundation Or Crawl Space More Secure?

A slab foundation can be considered more secure because it is one layer. A crawl space foundation is load-bearing and the load isn’t spread out across the entire slab. Instead, there are half-walls that support the house.

How Thick Does A Slab Foundation Have To Be?

Six inches is ideal for most concrete slab foundations. Thinner can work in some cases but thicker than six or thinner than four isn’t recommended. Speak with a contractor in your rea to find out the perfect thickness for your area.

Is A Crawl Space More Useful Than A Slab Foundation?

It can be. It all depends on your climate and your needs. If you have a mild climate and want easy access to utilities then a crawl space is usfel. If you live in a cold climate, a crawl space may do more harm than good.