Finishing Fiberglass Doors

Must Be Clean

The fiberglass door must be perfectly clean to achieve the best results. You can do it with a standard soap and water solution such as Top Job, Dawn Dish Soap or any other liquid type soap. Rinse the door with clear water and dry it. The door must be dry before you stain it.

Most fiberglass doors allow you to use mineral spirits to clean the door, but never use turpentine! Follow the finishing instructions that come with your door if you have them.

Stain Colors

If you have a new door, look at the stain kit. Most have some sample pieces of fiberglass. You use one of these to test the stain color. If you don't have a scrap, well, you may be out of luck. If the hinge edge is fiberglass (most are), then you can try to sample the color near the bottom of the door on this edge.

Stain color can be adjusted by the amount of time you allow the stain to sit on the door / sample before brushing and how much pressure you apply when brushing. If you want a lighter color, let the stain sit for a short while and remove lots of it with the brush. Do the opposite for a darker look.

The stain is applied to the door with a cloth rubbing it in a circular motion. Work from the center of the door to the outer members. Don't try to do the entire door at once. Work in small areas and feather out stain in overlap portions. Don't forget to stain the fiberglass sample. You will need this finished as well as the door. You will use the sample to test the door for gloss loss due to exposure.

Stain Must Be Dry

Most fiberglass stains need 48 hours to dry. You can test for dryness by applying a piece of masking tape to the door or better yet, to the fiberglass sample. Rub the tape with a piece of wood or knife handle. If the stain is dry the tape will be clean when you pull it off the stained object. If the stain is dry, you are now ready to go to the final steps.

Applying the Top Coat

Here is where many people goof up. The temptation is to apply thick coats of finish to protect the door. Most fiberglass door manufacturers want you to apply two thin coats. Thick coats will not dry properly. Try to coat the door in a dust-free environment if at all possible.

The top coats often look like thin milk. Do not panic! If you apply them sparingly they will dry crystal clear. Avoid dipping the entire brush in the clear coat. Try to just get the tip of the brush wet.

Work quickly and do not over brush. Apply some in an area and move on. If you brush back and forth over the same area too much, you can dissolve the stain! Always brush in the direction of the grain! Work from the center of the door out towards the edges.

Don't forget to apply a clear coat at this time to the fiberglass sample if you have one.

The Second Coat

Follow the instructions on the top coat container. Many will indicate a short drying time of less than 4 hours.

Do not sand the door after the first coat. Apply the final coat as you did the first coat. The surfaces normally look wet when you apply a thin coat - not milky. A milky appearance may be a clue that you are applying too much finish.

Painting a Fiberglass Door

Several readers wrote to me asking if they can paint a fiberglass door. Absolutely!

You paint one as you would any exterior surface. Clean the door with soap and water and allow it to dry.

Use a latex primer matched to a 100 percent acrylic top coat paint. I always like to remove the weather-stripping if at all possible. This allows you to work more quickly and keeps the door from sticking to the weather-stripping.

Keep the weather-stripping out of the door if at all possible for a week to 10 days. This drying time will allow the paint to fully cure and harden. If the paint is tacky it can stick to weather-stripping.