How to Lay a Concrete Slab

22 Jun 2020

How to Lay a Concrete Slab

Laying a concrete slab is one of the fundamental skills for DIY projects and home improvements.

Whether you’re setting up a garden shed, installing a small sidewalk, or fixing your driveway, knowing how to lay a concrete slab is incredibly useful.

But it’s important to know how to do it right. If you don’t do it correctly, then you could make a big mess that will take even more time and money to fix.

Here’s a simple guide for how to lay a concrete slab properly.

What You’ll Need 

  • Wood Slats 

  • Pegs 

  • Crushed stone 

  • Cement mix 

  • Rebar 

  • Binding wires 

  • Hammer 

  • Nails 

  • Spray paint 

  • Spirit level 

  • Wooden float 


  1. Prepare the site.

    Once you’ve chosen the site for your concrete slab, prepare it for further work. Clean the area and remove as much loose debris as possible to create a flat and solid area to build on.

  2. Build a box frame.

    Using wooden slats and nails, build a box frame that will enclose your concrete slab. Make sure that your box frame is completely square by checking that the distance between diagonal to diagonal on both sides is the same. After building this box frame, lay it over your site.

  3. Mark and excavate.

    Use spray paint to trace around your box frame and mark it. This will indicate where your frame will sit. Remove the box frame and excavate the area inside the spray-painted borders. Dig as deep your concrete slab requires. After excavating the site, place your box frame on top of marked borders.

  4. Secure the box.

    Secure the box in place by planting pegs on each side to support it.

  5. Level the frame.

    Use a spirit level to make sure that your frame is sitting level on the ground. Once you’ve adjusted and levelled your box frame, screw the frame with the pegs to hold it in place. Do this for all sides of the frame.

  6. Add crushed stone.

    Once your box frame is set up, add a layer of crushed stone at the bottom of the site and pack it down.

  7. Lay first layer of concrete.

    After preparing your concrete mix, pour it over the crushed stone as a first layer. Fill it only halfway up your box frame.

  8. Add reinforcement lattice.

    Add a reinforcement lattice (sized to fit inside your box frame) made of rebar to strengthen your concrete slab and prevent it from cracking. Tap on the lattice to make sure it is embedded into the first layer of concrete.

  9. Pour the rest of your concrete mix.

    Add the rest of your concrete mix into the frame and pack it down.

  10. Level the surface.

    Flatten the surface with a straight edge to make sure it is flat. You can do this by starting on one side of the frame and shaking the straight edge from side to side all the way to the other side of the frame. This will help level the surface and make sure any voids in the frame get filled. After levelling the surface, tap the sides of your box to release any trapped air bubbles.

  11. Let the concrete cure.

    Allow the concrete to cure for two weeks to make sure it’s ready to bear any load or weight.

  12. Remove the box frame.

    Once your concrete has cured, you can remove the box frame by unscrewing the pegs and breaking the box frame apart carefully.


And that’s it – you’ve successfully laid a concrete slab!

Got any questions?

Need advice on how to lay concrete properly and the right equipment for it? Contact us today to get more information.