Painting a fiberglass RV is, at first, labor intensive as you prep the exterior for priming and painting. Once that step has been completed, spraying on primer and paint is a straightforward process. You’ll need a few days to finish the job. Repairs will need to cure, and the primer and paint must dry between steps.
Preparing the Fiberglass for Paint
Begin by cleaning the RV with detergent and warm water. This is most easily done with a power washer. If you don’t own one, you can rent from a home improvement store or tool rental store. Pick up a paint sprayer attachment as well as the pressure washer attachment if the washer isn’t also a paint sprayer. If a power washer isn't available, a long-handled brush or sponges will suffice. Once the fiberglass is clean, rinse it thoroughly and let it dry.
Sand the existing paint lightly with fine grit sandpaper in the 220- to 400-grit range to create a surface the new paint can adhere to. Take care not to sand down to the fiberglass under the paint. If you discover dents or dings when sanding, repair them with a fiberglass repair kit and allow them to cure for at least 12 hours.
Wipe off any sanding residue from the areas to be repainted.
Tape off the windows, lights and any trim you don’t want to paint or get paint on. Mask all glass with heavy paper or plastic.
Painting the Fiberglass
Prime the RV with a urethane primer. Many manufacturers sell fiberglass primer. Just make sure the one you choose is waterproof, or marine-grade, and that it saves a step by not requiring sanding before application of the final coat of paint. Use the paint sprayer to apply an even coat of primer, spraying back and forth horizontally. Allow the primer to dry for the length of time recommended by the manufacturer.
Once the primer is dry, paint the RV using the same even strokes you used when applying the primer. Allow the paint to dry completely before adding any decals.
A paint sprayer is a better tool for painting fiberglass than a brush or roller because, when used properly, there will be fewer drips or runs in the paint. Remember to clean the spray nozzle after each use.
Fiberglass Painting Precautions
Wear a face mask when painting, and expect overspray from the paint sprayer. Work outside on a calm day, or at least downwind, to reduce the risk of spraying things other than the RV.
If you have the manufacturer’s paint code and want to match the original paint job, see if the place where you buy the paint can duplicate it. This can be important if you’re painting a Class C RV and want the body to match the cab.
Before painting the roof, determine whether it’s fiberglass or metal. Metal roofs require a different treatment.