Concrete slabs have many functions. In some areas they are the primary kind of house and commercial building’s foundations. They are also popular for outside shed floors, patios, and pool decks. Knowing how to pour a concrete slab is just one of the things a DIYer must know when undertaking a project to install a slab.
The first thing to realize is that a concrete slab is, for all intents and purposes, a permanent object. Everything must be planned in advance. Is there any plumbing to go into the slab? Is there any electrical conduit to be running through the slab?
All these things must be taken into consideration and be in place before the concrete slab is poured. If anything is overlooked, the concrete will have to be partially broken up to allow the changes to be implemented. Then that section of the slab must be re-poured, a laborious process and not one you want to be faced with!
Determine the Location of the Slab
The first thing to do is determine the slab’s location and size. Lay it out with stakes at the corners and string connecting the stakes. This will define the boundary of the slab. Be sure that the slab is square by using the 3-4-5 method and make adjustments as needed.
Prepare the Ground
Remove all the grass and other vegetation in area the slab will occupy. The dirt should be smooth and level. Dig a trench within the perimeter of the area. It should be a shovel widths wide and at least four inches deep. This is the footing of the slab and its purpose is to give the slab strength and stability.
Some areas require a vapor barrier to be placed on the ground and in the footing. Check with your local building code to verify whether or not this is a requirement that applies to your project.
Some steel mesh should be set in the footing and wired together at the corners. In large projects such as home construction, reinforcing bar (or rebar) is used but for a small patio or shed foundation, lighter gauge steel mesh is acceptable. This mesh gives the footing additional strength.
Build the Form
All concrete slabs require a form. What is a form? You can think of it as a mold. It is what keeps the wet concrete in place while it dries and cures. You will use 1” X 4” lumber to form the sides of the form. Let the string be your guide for placement.
Nail the ends of the form together for stability. Drive stakes into the ground every couple of feet on the outside of the form to keep it perfectly straight. This will hold the pressure exerted by the concrete as it is poured.
It is important that the top of the form be level all the way around. Make any adjustments needed to ensure this and then nail the stakes to the form to keep it in position.
Pour the Concrete
A local home improvement store or tool rental store should be able to furnish you with a portable cement mixer. Get it in place and position the chute to dump the wet concrete into the form. Start pouring into the form and work it into all areas.
After the form is full, level it off using the edge of a 2” X 4”, working it across the top of the form in a sawing motion from one end to the other.
For a super smooth finish, use a concrete float and trowel.