Crawlspace vs. Slab vs. Basements

Houses can be built a number of different ways. Location, soils, natural disaster probability and weather play a big role in what type of construction is used to build a house but in general there are 3 main styles that are used: the crawlspace, slab-on-grade and basement options.

Where I live, all three options are used frequently for a variety of different reasons but where you live, there may be one of these options that is most common based on a number of reasons. If you are looking to build a house though, it’s good to understand the 3 different types and make the choice that works best for you and the area you live in.

Here are some common pros and cons to each method:

Crawlspace:

The crawlspace option is usually done by building a wood floor over the footprint of your house from foundation wall to foundation wall, providing at least an 18" space between the bottom of the floor framing and the soil below. Thus, creating a crawlspace.

A crawlspace is a great option. It’s actually what I used when I built my house. I wanted to be able to get under the floor to add wiring or run whatever items I felt necessary down the road so having access was a major plus. The other bonus is the wood floor. It has more bounce and warmth than concrete and since we were installing a lot of tile, I wanted as much warmth and flex as I could get.

A crawlspace can also be built in a couple of different ways. One is a conditioned crawlspace and the other is a vented crawlspace.

Conditioned crawlspaces are not allowed in the city where I work so they are few and far between. My parents have one though and I can’t say one way or another if it's better or worse than a vented crawlspace. The pros are that it is conditioned. It should keep your pipes from freezing in the winter months and also create a complete envelope to keep critters and bugs out. The big negative is that a conditioned crawlspace doesn't provide an outlet for moisture to escape which will sometimes require additional HVAC components to keep the space dry.

Slab-On-Grade

A slab-on-grade is the process by which you backfill inside your foundation walls and pour a concrete slab to create the floor. This could be a great option for a number of reasons. I personally like a slab because it won't squeak like a wood floor and it’s the perfect scenario for radiant floor heating! For those of you who do not have a preference, it may also come down to cost. Is concrete or wood more cost effective?

Though a slab-on-grade may have better energy savings than a crawlspace, areas with cold weather may not be ideal for a SOG. If the ground under your slab is not insulated properly and it freezes, the slab can (and will) crack and move.

Basement

A basement is where you can get the bang for your buck if you are building a house. As long as you’re not on solid rock or in an area with a high water table, a basement can be a great way to add additional square footage to your house at a cheaper cost than building side to side or even up. The difference between a crawlspace and a basement is a higher foundation wall, some windows and stairs, a concrete slab, and some plumbing rough-in for a future bathroom. You will have to insulate the walls but get to omit the floor insulation that a vented crawlspace would require.

One code concern is unfinished basements with an engineered floor system above. Truss joists are required to be protected with drywall prior to final. The use of dimensional lumber on the other hand does not require the drywall allowing you to leave the entirety of the basement unfinished until you are ready to get to work!

Happy building!