The pouring of a slab on grade is an essential operation when building a terrace or installing the foundations of a house. However, it is not a job for neophytes. Some mistakes can lead to imperfections and cracks in the slab. To make your construction a success, read this article which presents the 5 steps to follow.
Making the Formwork
The first step in installing a slab on grade is to make a formwork. You will need crushed stones, pebbles, or gravel for its constitution. This layer of gravel will level the ground before the slab is built. This thickness of aggregate forms the base of the future slab on grade and ensures its stability and resistance.
The rubble should be spread evenly over the entire surface of the slab with a rake. Place a mixture of gravel and sand about 3 to 5 cm thick on top. Depending on the area involved, use a tamping machine or a manual tamping machine.
Making an Insulating Bed
The insulation is an unavoidable phase. To insulate your bed, two solutions are available. The first is to directly install a solid insulator such as extruded polystyrene or expanded polystyrene sheets on the draining form you have previously made.
With this option, you can apply a floor covering or a thin screed on the invert. The second and less common option is to use the insulation to the invert. This reduces thermal bridges.
The Installation of Insulating Slabs
The installation of a slab on grade involves the installation of a formwork. This is used to delimit the slab and contain the concrete until it dries completely. It is essential for an exterior slab. It can take various forms: insulated board, simple board, or traditional wooden formwork.
Its cost, close to zero, characterizes the latter, but its implementation time is somewhat long, and it presents a random finish after form removal. As for the insulated or simple boards, they represent an additional cost. However, they offer two advantages: they guarantee an impeccable finish and quick install. In addition, thanks to insulated boards, thermal bridges are eliminated.
The Use of a Metal Reinforcement
Concrete resists well to compression, but it is much less resilient to traction. To reinforce its mechanical properties and to avoid any structural problems, you must attach reinforcing bars to it. For the reinforcement of a slab-on-grade, welded wire mesh should be purchased.
The diameter and spacing of the reinforcing bars must be calculated according to the dimensions of the future slab. When making the metal reinforcement, you must ensure that the welded mesh is well covered with concrete. This will prevent the concrete from bursting due to the contact between the air and the steel.
Making a Concrete Slab
To make the slab, start by calculating the quantity of concrete needed. After calculating, pour the prepared concrete into the centre of the slab and spread it with a rake. Use a large ruler to smooth it out.
Continue pouring and levelling the concrete as you go until the form is filled. Then, proceed to the smoothing with a float and let it dry for at least 24 hours before removing the formwork and placing the foot on the slab. The installation of the covering must wait 1 to 2 months.
All in all, follow the five steps presented above to install your slab on grade successfully.