SLAB-ON-GRADE ONE STABLE CHOICE FOR FOUNDATION
Interesting option for homeowners who prefer to live without a basement
The foundation you pour is a key component to any structure on your property.
You want something stable — and strong — that will properly support the structure you build on top.
Here in Canada, you’ll generally see basement or crawl space foundations, but there is a third type you might have heard about: slab-on-grade foundations.
Slab-on-grade foundations forgo the basement foundation, and instead pour a simple concrete pad on top of a soil substrate, and build the structure on top.
They’re pretty common in areas with a high water table, or with poor soil quality — these are areas where you likely wouldn’t want a basement.
Other common structures that would be built on slab-ongrade-foundations are garages (mine is), sheds and barns.
Does a slab-on-grade pour make sense for your next build? Well, let’s weigh the pros and cons.
PROS
One big positive to no basement is you don’t have to worry about it getting flooded. With proper grading (the ground six feet, or 1.8 metres, from your home should be about three inches, or 7.6 centimetres, lower), and a good roof over your head, water should flow away from your home instead of penetrating any potential cracks found in your structure.
For a new build, slab-on-grade is a more economical choice.
You’re not buying all the concrete needed to pour the foundation, or taking on the cost of building that extra basement living space, plus all the building materials that includes.
Once the slab is poured, you’re ready for construction.
Slab-on-grade comes with a few green benefits — which I love. Not only are you using less concrete than if pouring a full basement, slab-on-grade provides a great base to passively heat a home. The slab pairs really well with radiant heating, creating a more cost-efficient and ecological way to heat your home.
CONS
The downside is that without a basement, those necessary systems to run your household will need to find a home elsewhere. I’m talking about your electrical wiring and your HVAC system. Without the basement, you’ll likely have a lot of wall space taken up by wires — not to mention you’ll need to carve out living space for your laundry and utilities. These can get noisy, so try to keep them away from bedrooms and invest in some good soundproofing insulation.
That said, you can place some of these systems, like your plumbing, in the concrete slab pad but that makes it really difficult to make any needed changes in the future.
Slab homes are much better suited for warmer climates than colder ones. Why? In climates that go through the freeze-thaw cycle, when the ground swells up during a frost heave, and then contracts again in warmer weather, it puts pressure on the slab that can lead to slab crack, and damage to the supporting structure.
Generally, you’ll want to pour a foundation that’s below the frost line, but above the water table. That’s not always possible, but it’s possible to build a slabon-grade that’s protected from frost heaving.
How? By installing skirt insulation, you can protect the slab from the freeze-thaw cycle and keep the temperature in the soil supporting the home consistent.
MISCONCEPTIONS
There’s this idea that because there’s no basement, a slabon-grade home eliminates the risk of radon gas seeping into a home. All homes, no matter their construction, can have dangerous levels of radon gas. Radon gas can seep in through foundation cracks, exhaust pipes and even well water. There’s no indication as to whether your home contains dangerous levels of radon without testing for it.
Similarly, just because your home is slab-on-grade, that doesn’t mean it’s safe from termites.
These little pests are resilient: If there are any cracks in your slab, they can find a way in. They can even sneak in through plumbing or other utility entrances.
Every structure needs to start with a strong foundation.
You never want to cut corners when it comes to your building envelope. Do your research, build it right, and protect it against the elements.