Ask the Builder
Staining Fiberglass Doors
By Tim Carter
©1993-2008 Tim Carter
Summary: Clear coatings on fiberglass exterior doors take a huge beating - especially clear coatings behind a storm door. I have seen traditional clear finishes and plastic parts on doors melt from the sun's heat. Acid rain, ultraviolet light, and other atmospheric pollutants simply erode clear finishes on fiberglass doors, polished brass and many other outdoor items. The key to minimizing restoration work lies in keeping up with the clear coatings.
Related Articles: painting fiberglass doors, fiberglass paint stripper, fiberglass door maintenance
Three - Five Years They Say
Many fiberglass door companies maintain that the clear coatings that protect the stained finish on their doors only lasts for 3 - 5 years. I feel that is a very fair statement. In fact, under certain conditions, they may be generous. I can think of locations where after 2 years you could be re-coating a clear finish. Heavy industrialized areas, west facing doors in the Southwest, fiberglass doors within 1/2 mile of ocean salt spray, etc. are examples.
The problem with many exterior items - including fiberglass doors - is that there is really no such thing as maintenance free. That is a sell line used by far too many salespeople when you look at things like vinyl siding, aluminum gutters and fiberglass doors. The truth is that all of these things require periodic cleanings and possible touch-up work to keep them looking superb.
Keep Up With It
The clear finishes that are applied to fiberglass doors are not much different than any off the shelf urethane. They are applied in thin coats and thus the amount of material left exposed to the elements is minimal. If you let the finish wear down to the stain, then you often have to strip the door and start over. Periodic thin maintenance coats of the clear finish every two years can save you tons of work. All you need to do is to make sure the door is squeaky clean before you apply each maintenance coat. Weather conditions should also be favorable.
The 50 - 90 F Rule
The largest manufacturer of fiberglass doors is a company called Therma-Tru Corporation. Their finishing instructions are very clear about temperature ranges for applying the stain and clear coats. They want the air temperature to be no less than 50 degrees and no more than 90 degrees when you work with their finishing system. Ideal conditions in my opinion would be 70 degrees with no wind and overcast skies.
Wind and direct sunlight can be your enemies when trying to get perfect results. These weather conditions can cause the clear finishes to dry too quickly. This can cause you to pull out your hair when you are working on the door. Wind can also blow dust and debris into a wet finish. Do whatever it takes to try to work in ideal conditions or create an artificial environment where you can work on the door immune from unfavorable temperatures, sunlight or wind.
The Stain Sample
If you are buying a new fiberglass door or a house with one, make sure you get the sample fiberglass skin or sample that comes in the finishing kit. This sample is supposed to be stained and finished just like the door and with the same ingredients. The sample is used to judge the level of clear coat degradation each year. You keep the sample inside in a dark location and free from heat and water. Each spring you pull it out and hold it against the exterior of your door. If you see that the gloss of the clear coat has begun to dull, it is time to re-coat the door.
No Mixing & Matching
When it comes time to re-coat your door, don't just use any clear coat. It is important to use a clear coat that is compatible with your existing finish. Keep good records or store the left over clear coat for your next application.
Keep in mind that many clear coats have a limited shelf life. Some state a three year life span once opened. I would not use one that is over two years old. Why take a chance? Remember, these clear coats are simply a hybrid glue. If you want them to stick well, then use fresh materials. I wouldn't take a chance with old material unless I had to.
