How To: Paint A Masonry Sill

What you will need

  • Masonry paint
  • Dust sheet
  • Wire brush or coarse sandpaper
  • Masonry paint brush
  • Masking tape
  • Stabilising solution (if required)


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  • 1 Sometimes paint on a window sill can become chalky or begin to flake and look unsightly. This can be rectified quite easily, and if done correctly you can achieve long lasting results. Before starting work lay a dust sheet under the window sill.
  • 2 Remove any flaking paint using a wire brush or rough grit sandpaper. Wipe away any dust with a cloth or brush.
  • 3 If there’s any mould or moss remove as much as possible by scraping and brushing before treating with a fungicidal wash.
  • 4 Mask off any areas that you don’t want to get paint on.
  • 5 To treat a chalky surface, apply a stabilising solution to the window sill using a brush. Leave the stabilising solution to dry for the time indicated in the manufacturer’s instructions.
  • 6 Stir the Window Sill paint thoroughly before starting and use a good masonry brush for painting. Alternatively you can use a standard masonry paint on your sills and follow the same procedure. Top Tip: Run the paint brush along the ground first to remove any loose bristles.
  • 7 When applying the paint, don’t overload the brush or apply the paint too thickly as it will always take two coats at least for optimum coverage.
  • 8 Leave the paint to dry after the first coat for the time indicated on the tin.
  • 9 Once the first coat has dried, apply the second coat. You can remove all the masking tape once you have finished painting the final coat.
  • 10 Now your masonry window sill is completely painted.