In today’s post we will continue on discussing the anatomy of the most common types of foundation for residential buildings. Leaving behind Pier and Beam we shall focus on the nature of Slab on Grade foundations, what they are, how they are built along with their pros and cons.
Like Pier and Beam, Slab on Grade is also a type of shallow foundation It basically is a concrete slab, poured in a single piece and resting directly on the ground below. It is a pad that consists of a layer of 4’’ to 8’’ of concrete and is anchored by underground concrete columns called footings witch outline the perimeter and are around 18’’ to 2 feet deep.
The reason they are so common is because of how relatively cheap and easy to build they are. Given that there is no crawl space or basements needed, the time and excavation and labor costs lower dramatically. The simplest of these types of foundations are constructed by pouring directly onto prepared soil and while other foundations might have extra elements like supporting concrete feet or insulating form, basically all types of slab foundations are the same: a large block of concrete without open spaces underneath and where the rest of the structure of the house will sit upon directly on top.
As mentioned, one of the several benefits of this foundation is the price, as they are extremely cost effective, and far cheaper than basement or pier and beam foundations. Also, building times are more effective as many of these foundations can be completed with a single pour, equaling less time spent on waiting for it to dry and faster construction times.
Besides, the fact that there aren’t any open spaces underneath the house, the risk of infestation lowers dramatically. Sure, insects and critters can always see this as a challenge and persist in finding a different way into your home, but at least you will not find any nests or hives in crawl spaces or basements.
Other positives are less risks of damages from flooding or leaking gas from non existing basements or crawl spaces, and as long as you keep an eye out for cracks, not much maintenance has to be done for slab foundations.
However it does have its cons, among which you will find sewer and drainage piping problems, and since, unlike crawl spaces for instance, there is no direct access to them, it means that the slab will have to be cut into to access them and get them repaired when needed.
Then comes soil settlement; if the slab is not poured at the proper depth then it may be too thin and susceptible to cracking due to the soil shifting and settling, and which could in turn bring upon different issues like sagging ceilings, bowing walls and crack both in the foundation itself as well as the exterior walls of the structure.
Generally, Slab on Grade foundations are more often used on warmer climates, and the reason why is because this type of foundations are susceptible to ice damage. With specially cold weather, slab foundations are prone to cracking. Freezing temperatures and moisture can create serious cracks in the foundation. Given that the foundation rests directly on the soil below, moisture might become an issue as concrete is porous, and if the slab is not properly insulated moisture can move up the slab and into the living area. One of the methods to fight this is to build the foundation over a layer of sand or grave, so that water can drain from underneath the foundation.
While some cracks are to be expected, you always have to be on the lookout to see if they are not the first symptoms of a larger and deeper problem. But if the cracks are still small, however, it is easy to repair them with some epoxy resin. However you should never get to comfortable about this, and it is highly encourage that you call a licensed contractor for a proper inspection. After all, larger underlying issues with cracks can require full on foundation repairs like installing piers to level the foundation, and while rebar and wire meshes are not standard to slab on grade foundations, there might come a time when they are required to be installed during a foundation repair.
So don’t let the problem become a major issue and call the experts! Inspections, foundation repairs and additional services are our fields of expertise; give us a call and your home and foundation will thank you for years to come!