How to Lay a Concrete Foundation

slab foundation
  • 20-80 hours
  • Intermediate
  • 2,000-20,000
What You'll Need
Cement mixer

The concrete foundation is the most important part of any building. It is a solid base that will support the whole weight of your building. Any weaknesses in the concrete foundation will cause problems for the entire structure. This article details the steps you follow to build a foundation that won't let you down.

Plan the Concrete Foundation

Decide on the size and thickness of the foundation. The dimensions will depend upon the type of structure you are building and the land upon which you are building. Ensure that the concrete slab is thick enough to support the building and that there aren't any weaknesses that could later pose a problem.

Dig the Trench

leveling off poured cement

After you determine the size and thickness of the concrete foundation, start digging the trench. Dig the trench twice the depth of the concrete slab you will pour. If you see any stones or pieces of trash in the hole, remove them.

Prepare the Trench

Prepare the trench by adding some sand at the bottom and placing a membrane over the top. This technique will prevent water damage.

Make the Frame

Construct a frame from wood. Use the frame to constrain the concrete while it dries. The frame is easy to make, and it will be even easier if you build it in place.

Use stakes to hold the frame in place. Make sure that none of the liquid will be able to escape. Use extra pieces of wood as screeding bars, which will ensure that the concrete is smooth and level.

Mix the Concrete

concrete mixer and wheel barrow

You can mix cement by hand, but you probably won't want to do so for the large amount you’ll need. Instead, either hire a cement mixer or purchase ready-mixed concrete, which can be poured directly into your hole from the cement-mixing truck.

Level the Concrete

Use the screed bars to level the concrete in the hole and allow the entire thing to dry. You will be left with a completely level concrete slab of the exact dimensions required. If you encounter any high or low patches, sand them with an electric sander. If you find any holes in the concrete foundation, use a self-leveling compound to smooth these out. Do not use a very thin layer of concrete because it will chip very easily.