Because fiberglass garage doors are smooth and nonporous, they are highly resistant to primer and paint adhesion. If you wish to remodel your fiberglass garage door with a coat of paint, you will need to dedicate yourself to proper surface preparation, or your painted finish will chip and flake away. In addition, because fiberglass garage doors are slick, you should use a particular application process that will encourage a nice-looking finish free from sags and brush marks.
Things You'll Need
Heavy-duty fabric dropcloths
Blue painter's tape
Acrylic latex primer
2 nap roller covers
4-inch latex paintbrush
Acrylic latex paint
Clean the garage door with water and dish soap. Rinse the fiberglass using a water hose. Allow the door to dry.
Encourage primer and paint adhesion by roughing up the fiberglass door using sandpaper. Load a fine-grit sandpaper into a palm sander, and abrade the fiberglass until it feels slightly rough.
Elevate the garage door high enough to slide dropcloths underneath. Close the door once the drop cloths are in place. Cover portions of the fiberglass garage door that you want to remain unpainted with painter's tape.
Apply a latex primer to the abraded door using a roller. Smooth the wet primer with a 4-inch paintbrush manufactured for use with latex water-based coatings. Raise the garage door 1 foot. Wait two to three hours for the primer to dry.
Clean your painting tools with water.
Apply acrylic latex paint to the primed fiberglass garage door using the roller. Use a new roller cover. Apply the paint as you did the primer. Raise the garage door 1 foot. Wait two to three hours for the paint to dry.
Do not choose a sandpaper with a grit below 300, or you may scar the fiberglass garage door.
Failure to raise the door during the drying process can cause the seams to stick shut.