Concrete formwork is an easy way to make a concrete slab. This can then be used as a support for a construction, a swimming pool or a terrace, among other examples. To do this, you will have to lay out and assemble planks before pouring your concrete prepared by you or delivered ready for use. Here are our advice on equipment and the steps to follow to make your concrete formwork.
How to equip yourself to make a formwork for concrete?
Making a formwork for concrete is a relatively simple operation that requires few materials. The formwork is generally made using simple wooden planks, or even PVC or aluminum. These three materials are ideal for making a formwork as long as they are strong enough to support the weight of the concrete and waterproof. However, wood is the most common.
The commercially available shuttering boards measure 2 and 4 meters long, 10 to 30 cm wide and up to 4 cm thick. So choose the boards most suited to your needs, knowing that you can cut them if necessary.
You will also need concrete, which you can have delivered ready-to-install or which you can prepare yourself by mixing sand, cement and water in a concrete mixer.
To prepare your boards, you will need a jigsaw to cut them to the correct length, a drill to assemble them or, if necessary, a hammer and nails. Also plan to apply oil to the boards to facilitate their removal during stripping. Do not hesitate to plant stakes to clearly delimit the area and keep the boards in place, especially if the surface to be covered is large.
You will also need a shovel and a spade to clear the area, and ideally even a mini digger. Finally, a spirit level will allow you to check the flatness of the formwork.
How to make formwork for concrete?
To make your concrete formwork, you will need to follow the following 4 steps.
Step 1: prepare your surface
You will not be able to lay a concrete formwork without carrying out the earthwork of the area first. Place stakes to delimit it well and unload to a depth of at least 20 cm using a shovel and a spade or, if the surface is large, a mini-shovel.
Step 2: laying the boards
Your boards will allow you to make the formwork easily. Buy them beforehand and choose them in the dimensions that correspond to your needs. Make sure they are strong enough to support the weight of the concrete.
Cut them according to your needs using the jigsaw and assemble them by screwing or nailing them to achieve all the circumference. Guide yourselves by the stakes delimiting the zone and place your boards in the open space. Check their flatness with a spirit level, as the top of the boards should match the edge of the concrete slab. If the area is large, add stakes along the boards to keep them in place and prevent concrete from breaking, cracking or deforming them.
Finally, once your boards are in place, you can oil their interior surface. It will then be easier to remove them when the tile is dry.
Step 3: pour your concrete slab
The concrete mixer is convenient for preparing your concrete yourself by mixing sand, gravel and cement. It is possible to rent one for several hours or several days if you do not have one. You can also opt for a direct delivery of ready-to-install concrete using a mixer truck. The latter solution is only advantageous for large surfaces, because the delivery is expensive. Better therefore that it is profitable.
With your formwork in place, you just need to pour your concrete into it. With a stick or stake, prick it in places to ventilate it well.
With a float, smooth the surface of the slab and then let it dry without touching it again. A small slab needs 2 to 4 days to be perfectly dry. For a thicker slab, allow 7 to 10 days. Be careful not to walk on the slab until the drying is complete.
Step 4: remove your formwork
When the slab is perfectly dry, it is time to strip it. With a small sledgehammer, tap the sides of the shuttering boards to loosen them from the concrete. If they have been well oiled, their removal will be easier.
Be careful, however, to measure your movements carefully so as not to damage the slab. Concrete is indeed a friable material and its edges are fragile.
You can now affix a construction on your concrete slab (garden shed, swimming pool, garage, shed, carport, etc.) or cover it with a coating of your choice to make it a terrace, a pond deck, etc.