How to Build a Large Concrete Slab

Written by alexander callos | 13/05/2017
How to Build a Large Concrete Slab
Pouring a large concrete slab takes time and preparation. (cement,concrete image by Greg Pickens from

Concrete slabs are used for many different applications, including sidewalks, driveways, garage floors and patios. Proper installation will take time and experience--as well as preparation. Pouring a concrete slab is a job that will take more than one person and, often, professional installation is recommended.

Decide on the how big the large concrete slab will be and measure the area it'll cover, marking it with a chalk line. Set stakes in the ground every couple of feet around the perimeter. Nail scrap lumber such as 2 by 12s to the stakes. This will be the form for the concrete.

Dig out the area where the concrete will go. Dig six inches into the ground to allow room for the gravel and the concrete to be poured. Dump in a layer of gravel along the bottom to help with drainage. Cover the gravel with a 6-mil polythene sheeting.

Tie two pieces of rebar with tiewire along the perimeter of the form. This rebar comes in 20 foot lengths and should span the entire area of the slab. This will help reinforce the concrete once it is poured. Cut the rebar with a circular saw and a metal cutting blade, if necessary.

Mix the concrete with water into a wheelbarrow and begin in the back left corner of the form. Working left to right and back to front, begin pouring the concrete into the form. Spread out the concrete with a rake and level the concrete with a flat 2 by 4 as it is being poured. This part of the job requires multiple people.

Remove the marks left in the concrete with a bull float as soon as everything is poured and spread. This will completely level out the surface. Work the bull float along the surface to square everything off. Edge around the inside of the form with an edging tool until the edge is completely smooth. Allow the concrete time to dry and smooth out the surface with a magnesium float. Work in a circular motion, pulling up with the float at the end of each motion. Allow the concrete ample time to dry before applying any weight to it.

Things you need

  • Tape measure
  • Circular saw
  • Safety glasses
  • Level
  • Hammer
  • Pry bar
  • String line
  • Gravel
  • Rubber boots
  • Concrete
  • Tie Wire
  • Nails
  • Bolts
  • Rebar
  • 6-mil plastic
  • Scrap lumber
  • Chalk line
  • Gloves
  • Bull float
  • Edger

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