How to Skim Coat a Concrete Slab

Repair imperfections and prepare for decorative overlays with a concrete skim coat.
Repair imperfections and prepare for decorative overlays with a concrete skim coat. (Image: Siri Stafford/Lifesize/Getty Images)

Applying a layer of skim coat to an existing concrete slab will cover pitted and hairline-cracked surfaces. The thin layer of concrete skim coat is commonly applied with a long-handled squeegee or trowel. These layers of skim coat are also suitable for stamping designs and patterns into the concrete. Homeowners with basic carpentry skills should be able to complete this project easily.

Things You'll Need

  • Safety goggles
  • Filter facemask
  • Protective gloves
  • Push broom
  • Floor grinder with medium abrasive pad
  • Pressure washer
  • Wet/dry shop vacuum
  • 5-gallon bucket
  • 2 bags skim coat mix, 20 pounds each
  • Power drill with mixing hook
  • Long-handled squeegee
  • Pump sprayer
  • Long trowel

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Put on safety goggles, a filter face mask and protective gloves to protect you from flying concrete particles and dust from the skim-coat mix. Getting the skim-coat mix in your lungs can cause respiratory problems.

Sweep loose particles, dust and dirt from the concrete slab with a push broom. Abrade the surface of the concrete with a floor grinder equipped with a medium abrasive pad. Move the floor grinder in even, slow, side-to-side motions to cover the slab.

Rinse the surface of the slab with a pressure washer to remove all of the grinding dust left by the floor grinder. Vacuum all standing water and puddles left from the pressure washer. Leave the surface of the concrete slab damp for the skim-coat application.

Pour 4 quarts of water into a 5-gallon bucket. Add one 20-lb bag of skim-coat mix. Mix the skim coat with a power drill equipped with a mixing hook until the mixture is a pourable consistency and free of lumps.

Spread a thin layer of skim coat on the concrete slab using a long-handled squeegee. Make sure you spread the skim coat into all areas of the slab for an even coat. Allow the skim coat to dry for one hour, or as recommended on the product's label.

Apply a second layer of skim coat if recommended by the manufacturer. Mist the concrete slab with a pump sprayer filled with water. Mix another bag of skim coat with water in the same manner as before, but lessen the amount of water by 1 quart. The second layer of skim coat should be slightly thicker than the first coat.

Spread the second layer of skim coat with a long trowel, making it uniform and smooth. Allow the second layer to dry according to the manufacturer's instructions.


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