Traditional Foundations vs. Monolithic Slab Foundations
A traditional concrete foundation consists of three parts: footings, foundation walls, and a slab. Footings are wide areas of concrete which dig deep into the earth. They spread the weight of your building evenly across the soil to prevent cracks and movement of the building. In climates with cold winters, they also act as a barrier to frost; the footings are buried deep into the ground below the frost line, or the deepest point frost is expected to penetrate. Without footings, or if your footings aren’t placed deep enough, water will go through freezing and thawing cycles. Each time it freezes, the water expands and creates pressure on the bottom of your foundation before melting again and leaving behind a cavity which the foundation will begin to crumble into. You’ve seen the damage freeze-thaw cycles can do to a concrete sidewalk, imagine that happening to your foundation!
Moving upwards, the foundation walls are thick sections of concrete which rest on top of the footings and connect to the rest of the building. These are the walls that you often see exposed in unfinished basements. Between your foundation walls and resting on top of the footings lies your foundation slab: the giant piece of concrete which makes up your basement floor or subfloor.
Each of these pieces must be poured and cure one at a time: a process that can take up to a week for each step. This whole process not only takes a lot of time, it also increases your construction costs! That’s where monolithic slab foundations come in. Monolithic slabs combine the foundation footings and slab into one piece, allowing them to both be poured at the same time and cut back your time and monetary investment.
THE MONOLITHIC SLAB CONSTRUCTION PROCESS
In addition to being poured in one step, monolithic foundations are also significantly thinner than a traditional foundation. They average only four inches thick and the footings only reach about 12 inches from the base to the top of the floor. This means you’ll only have to dig down about six inches and the entire thing can be done by hand if you’re motivated enough. The slab generally rests on a bed of gravel for improved drainage and is reinforced with wire mesh or rebar for extra strength and to reduce the chance of cracking. In cold climates like we face here in Colorado, you can combine internal heating with an extra layer of insulation around the perimeter of the foundation which artificially pushes the frost line out and away from the floor, keeping it safe from freezing and thawing cycles.