The foundation that your house is built on can have a major impact on the structural integrity of your home. A slab foundation is made of concrete that is typically 4”-6” thick in the center. The concrete slab is often placed on a layer of sand for drainage or to act as a cushion. Houses built on a slab lack crawlspaces, and there is no space under the floor.
Concrete slabs are more common in warm states where the ground is likely to freeze and cause the foundation to crack. In the Treasure Valley heating units are often used to keep the slab from freezing during cold winter months. Some houses don’t have a basement or crawl space under them but are simply built on a concrete slab – perhaps because the house sits on bedrock or a high water table. The concrete is poured onto the ground all at one time. Some foundations have post tension cables or are reinforced with steel rods called rebar so that the slab can bearing the weight of the house.
Some advantages of a concrete slab are that it takes less time for a concrete slab to dry. Less downtime means that construction can move along without delay. There is no need to wait the several days it takes for the concrete in a poured basement to cure and dry. Slab foundations minimize the risk of damage from flooding or the leaking of gas, such as radon, from a basement or crawl space into the house. A concrete slab can protect a home from termites or other similar insects as there are no open spaces underneath the house that provide access to wooden joists or supports insects could chew. Cost savings is one of the biggest advantages. In many cases, the home buyer can shave as much as $10,000 off the cost of the house. If it is built on a slab there is no crawl space or basement t budget for. This is particularly true when a builder has to carve a basement out of solid rock—a very expensive proposition.
Some disadvantages of a concrete slab are termites and other pests cannot gain access directly beneath the house, they can enter through the walls since the house is typically closer to the ground. This is particularly true if the siding is made of wood and sits on the ground. An air-conditioning unit and furnace may also have to be installed on the ground floor, which means that they will take up room that might otherwise be used for other purposes. One of the most significant potential disadvantages is if the slab cracks. This can substantially compromise the structural integrity of the house and be difficult and expensive to repair. Among the factors that can result in a slab cracking are tree roots, soil displacement, earthquakes, or frozen ground.