How to Paint Exterior Plastic Moulding

Updated February 21, 2017

When it comes to painting, not all surfaces should be treated the same. Unlike wood, which is rough and porous, plastic moulding is smooth and slick. This can cause problems with paint adhesion if you don't know the proper way to prepare the surface before you get started. In addition, it can be difficult for some do-it-yourselfers to apply a smooth-looking finish free of unattractive brush strokes because they tend to over-apply. If you need to paint exterior plastic moulding, there are a few simple preparation and application techniques you can employ that will help to provide you with a smooth, long-lasting finish.

Scrub the surface of the exterior plastic moulding with water and dish soap.

Rinse the exterior plastic moulding thoroughly. Allow the exterior plastic moulding to dry completely before proceeding.

Scrape away any loose or peeling paint from the exterior plastic moulding with a metal putty knife. Skip this step if the exterior plastic moulding is unpainted.

Abrade the surface of the exterior plastic moulding by sanding it with 80 to 120 grit sandpaper.

Pour latex primer into the painter's pale or 5-gallon bucket.

Use the 3 to 4-inch latex paintbrush to apply latex primer to the exterior plastic moulding. Apply a thin coat and use only slight pressure to promote a smooth-looking coat free of unattractive brush strokes. Allow the primer to dry for two hours.

Wash the 3 to 4-inch latex paintbrush with warm water. Massage the water deep within the bristles of the paintbrush using your hands.

Repeat Steps 5 and 6, except use latex paint instead of primer. Allow the paint to dry for two hours. Apply additional coats if necessary.


Be sure to rinse all the soap from the exterior plastic moulding. If you leave any soap on the exterior plastic moulding, you will have problems with adhesion.


It's important to abrade the surface of the exterior plastic moulding by sanding it with 80 to 120 grit sandpaper as this promotes adhesion. Never skip this step or you may end up with chipping and peeling.

Things You'll Need

  • Dish soap
  • Rags
  • Blue painter's tape
  • 80 to 120 grit sandpaper
  • Metal putty knife
  • Painter's pale or 5-gallon bucket
  • 3 to 4-inch latex paintbrush
  • Latex primer
  • Latex paint
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About the Author

Ryan Lawrence is a freelance writer based in Boulder, Colorado. He has been writing professionally since 1999. He has 10 years of experience as a professional painting contractor. Lawrence writes for High Class Blogs and Yodle. He has a bachelor's degree in journalism and public relations with a minor in history from the University of Oklahoma.