Several times throughout the year, we are often asked about doing a home with a slab-on-grade as the main surface for the home. Which is better? a crawl space, as we do, or a slab-on-grade?
Some will argue that a crawl space gives you more flexibility with the home, and its construction. For as many benefits there might be to a slab-on-grade home, the truth of the matter is, often the slab was not “placed” correctly to the approval of designer, builder and client. A lot can go wrong. Here is but a brief sample:
1. Cracking – structural
2. Cracking – shrinkage
3. Curling- Top of slab shrinks more than bottom and slab edge lifts.
4. Scaling – Hardened concrete breaking away from slab top in sheets 1/8” to ¼” thick.
5. Dusting – Appearance of powdery material at slab surface.
6. Crazing – Many fine hairline cracks in a new slab which resemble a road map.
7. Spalling – disintegration of concrete at joint edges.
To avoid one, if not all of the aforementioned items, the concrete must be placed appropriately. What this involves are a lot of variables. One of which is the appropriate mix of concrete.
Portland Cement Association recommends that a commercial or industrial concrete floor should have a three-day compression strength of 1800 psi. This is to avoid any damage before it thoroughly sets or hardens which takes 28 or so days. Some would say bad concrete will never result in a good finish. Therefore, a PSI of 4000, instead of what’s common 3000 psi, should be the starting point for a properly mixed concrete.
Not to go into a lot of detail here about concrete, but what are the benefits of have a slab-on-grade? Basically some would say the “ugly, dirty, moldy” crawl space won’t haunt you with a slab-on-grade floor. This may perhaps be true, but if you live in an area of high moisture, high water tables, lots of rain, then most, if not all, residential contractors in that particular area will not do a slab-on-grade home. The risk/reward are too great to take on such liability. That, and again, when pipes, conduit, and the 7 items mention above happen, things can quickly begin to spiral. It all starts at the foundation. Every framer will tell you “when the foundation is good, the framing goes good”. That and everything else that requires walls to line up, drywall to come together and siding to be installed without hiccups. Here at True Built Home, we are not opposed to perhaps doing one, under the right conditions, and in the right locations, particularly east of the mountains in our drier areas. If you are living in one of these areas, you might want to talk to one of our sales staff about doing one of our plans with a slab-on-grade. Please keep in mind, that if your thoughts are of saving money with a slab-on-grade floor, this is not the case. Typically, they cost a bit more that our standard crawl space homes.
Crawl space Better?
The flexibility you get with a crawl space are obvious. You don’t have to hack into the floor if something were to go wrong with the plumbing, or drainage. Being able to service the area of the home, via a crawl space, makes many people aware that having a crawl space is the easy choice. In addition, many think about the hardness of having a concrete floor, all day, every day, in the home. Thinking of standing, or laying down, or dropping things, just makes many cringe about the prospect of having a slab-on-grade home.
In the end, location, weather, land, and your particular taste will likely be the driving force of whether or not you have a standard crawl space home, or elect to have a higher end, and often more expensive alternative, slab-on-grade home.
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