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how to finish concrete

How To Finish Concrete

For your freshly poured concrete to look as smooth as it possibly can, you’ll need to learn all about the finishing process. Concrete doesn’t just form a neat slab shape all on its own, it needs some extra attention using a few tools and some patience. This guide should help you produce a perfect finish for your concrete, ensuring it’s as clean and durable as possible.

What you'll need

  1. A long, straight plank (a ‘2x4’)
  2. A bull float - one with rounded edges is preferable
  3. A hand float
  4. An edging tool
  5. A trowel or broom

Stage 1: Levelling

  1. First you need to remove overflowing concrete to level off the surface. Place your plank horizontally over the slab - making sure it extends over the forms on both sides - and perform a sawing motion, pushing and pulling the plank along the forms.
  2. Once you reach the end, push the excess concrete against the forms and leave it for a later stage.

Top tip Two people - one at either end of the plank - will make this stage easier.

Stage 2: Finishing

  1. Use the bull float to smooth out the surface. Move it back and forth between the horizontal forms until you cover the entire surface.
  2. Slightly lift the float so the leading edge sits at an angle when pushing and pulling.
  3. Use your edging tool to tidy up the corners and edges of the slab. Move the tool back and forth, tackling small areas at a time.
  4. Next, you need to cut control joints into the slab in order to prevent it from cracking. Joints should be evenly spaced at intervals no larger than three times the thickness of the slab.
  5. Control joints should extend from common cracking locations - inside corners, for example.
  6. Cut your control joints 25% through the depth of the slab - so for a 4 inch slab, joints should only be 1 inch deep.

Top tip This stage should be completed before any bleed water appears on the slab surface

Stage 3: Wait for the bleed water to evaporate

  1. As your concrete sets, bleed water will appear on the surface. Before moving on to the next stage, wait for this bleed water to evaporate. How long this takes depends on humidity, temperature, wind speed and the mix itself.

Stage 4: hand finishing

  1. Take your hand float and smooth out the surface once more with the same type of motion as before.
  2. Again, tilt the leading edge as you go and don’t press too hard on the concrete.
  3. Now it’s time to choose your finish. Will you go with a trowel finish or a broom finish?
  4. A trowel finish leaves a very slick surface. Keep in mind that, should this surface get wet, it will be slippery and a potential hazard to anyone walking over it.
  5. A broom finish leaves a rougher surface, one that is slip resistant and has a more rugged aesthetic. For footpaths, a broom finish is probably the preferable option. Choose a medium or stiff bristled brush so marks are left behind.

Top tip Trowel finish: Do two or three passes with your trowel - and wait for the concrete to slightly dry between passes. Broom finish: Drag the broom towards you, gently, and overlap the preceding area to ensure you don’t miss an inch.

Stage 5: Curing

  1. Concrete doesn’t reach optimal compressive strength immediately - it needs to be cured. Most mixes will have a 28 day cure period, but will be strong enough to walk on after 24 hours.
  2. Curing concrete means maintaining moisture content so the hydration process continues. One easy way to cure concrete is to dampen the slab and then cover it with a plastic sheet - keeping the sheet weighed down by bricks or other heavy objects.

Top tip Start the curing process as soon as you can. For driveways, keep vehicles off the concrete for the full 28 day cure period to avoid any chance of cracks or collapse.

Stage 6: seal the concrete

  1. Once the full 28-30 day curing process is over, you should seal the concrete so it’s protected from the elements - and is easier to clean.
  2. Follow the instructions on your chosen sealant - you may need more than one layer.
  3. Wait for the sealant to dry before walking on your concrete. It’s recommended to avoid driving on the concrete for a few days after sealing.