How to Lay a Concrete Slab

Written by etienne caron | 13/05/2017
How to Lay a Concrete Slab
( McMahon, Chris McSorley)

Whether you're building a sidewalk, a driveway or a basement, the procedures and techniques for pouring and finishing concrete are basically the same. Concrete starts to harden as soon as it is mixed so you need to pour and finish it as fast as you can. Have some friends or family help you if your project uses over 1 cubic foot of concrete.

How to Lay a Concrete Slab
The Form

Clear and level the work area. Moisten the ground and compact with the roller. Add gravel to cover the base, moisten and roll again. Put polythene sheeting over the gravel to provide a vapour barrier.

How to Lay a Concrete Slab

Drive wooden stakes into the ground along the outside edge of your project. Place 2 by 4s against the stakes and nail them even with the tops of the stakes. Lay concrete reinforcement wire on top of the plastic.

How to Lay a Concrete Slab

Dump the concrete into the forms while one person shovels and another person rakes the concrete into place. Use a brick trowel along the edges. Use the rake to pull the reinforcement wire up a little through the wet concrete so it becomes well-embedded.

How to Lay a Concrete Slab

Screed the concrete using a 2 by 4 that is long enough to cross the form and rest on the top edge. Screeding simply means moving the 2 by 4 back and forth in a sawing motion. Rake forward any excess concrete that builds up in front of the screed. Screeding makes the concrete level with the forms, fills in low spots, and forces the aggregates down and brings the cement paste to the top.

How to Lay a Concrete Slab
Finished Slab

Float the concrete when the surface water starts to disappear and the concrete loses its sheen. You should move the float in a circular manner against the surface until the cement paste works up onto the surface--the concrete surface will go from rough to smooth. A wood float works best for stubborn spots. Round off all the edges after floating.

Test the concrete with a finger after the water sheen has started to disappear. If your finger leaves a small impression, it's time to start trowelling. Use long, sweeping strokes with the blade held up at a slight angle. You want to smooth everything out as much as possible.

Let the concrete sit, free of traffic for at least three days. Driveways should cure for a week. Do not let the concrete dry out too fast--in warm weather, spray water on it twice a day. If you will be away, wet it and put plastic over it.

Things you need

  • Drum compactor
  • Gravel
  • Polythene sheets
  • Wood stakes
  • 2 by 4s
  • Concrete reinforcement wire
  • Metal wheelbarrow
  • Square shovel
  • Mortar hoe
  • Metal garden rake
  • Bricklayer's trowel
  • Wood float
  • Magnesium float
  • Metal bull float
  • Edger
  • Concrete finishing trowel

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