DIY Concrete Guide: Step 4 – Cut & Place Formwork

What is "Formwork"?

Formwork is the walls that support the concrete until its set. It forms a mould. The best material for formwork is timber at least 25mm thick and equal in width to the concrete thickness.

Formwork for Concrete Paths

  • Use structural plywood or hardboard.
  • For curved paths, hardboard or 7mm plywood is suitable but requires more supporting pegs.
  • Forms must be strong, smooth on the top edge and well supported with stout pegs. (A good test for the strength of formwork is its ability to withstand a reasonable kick).
  • Formwork must be deep enough to hold the thickness of concrete placed and to prevent slurry escaping underneath.

Plywood Formwork

Plywood formwork from your local building supply or timber yard is easy to cut to shape and can be reused for several jobs. You can cut enough formwork from a standard 2440mm x 1220mm sheet to make a path 1 metre wide and about 10 metres long.

  • Place the forms along the borders marked out with string.
  • 2) Secure forms in position with stout pegs driven into the ground inside and outside the forms.
  • The outside pegs should be placed at more frequent intervals and the forms nailed to them.
  • Hammer the pegs down to below the height of the forms.
  • Coat the formwork lightly with thin oil or form oil to be removed easily later.
  • Soak the ground and forms thoroughly with water - the night before the pour.
  • Dampen again before the Boral Concrete truck arrives. The ground should be damp but not muddy.

Place reinforcement (check if required)

Areas like garage floors require reinforcing with mesh or similar. Local building regulations sometimes demand the use of reinforcement.

For information on what types of mesh to use and how to cut and place it, contact one of the steel fabric mesh suppliers eg. Bluescope Steel.

Check your measurements

Once you’ve got the formwork sorted and a few other preparations are complete, do one final check on the quantity of concrete you require.

IMPORTANT! Check the THICKNESS. Remember - if your slab has an average thickness of 10% more than your original measurements you will need at least 10% more concrete to complete your job.

>Step 5 – Placing the Concrete
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>Safety Advice

Cutting up formwork