Painting fiberglass doors and steel doors: what the door makers say
· 7 min read · By GK Painting & Remodeling
Yes, you can paint a fiberglass door, and a steel one. Painting fiberglass doors comes down to a clean surface, the primer your door maker calls for, a quality exterior paint and mild, dry weather. Smooth fiberglass is paint only: Pella and Therma-Tru both say not to stain it.
The details are where it gets tricky, because door makers don't agree on sanding, primer or even the weatherstrip. Below is what each one says, what steel needs, and how Madison's weather fits in. For the basic brush and roller steps, see how to paint a front door.
Painting fiberglass doors: can you, and should you?
You can, and sometimes you have to. Pella's owner's manual says its smooth fiberglass doors and sidelights can be painted but not stained, and that painting is required. Its steel doors come factory-primed and can be painted but not stained.
If your door arrived unfinished, a clock is running. Pella says to finish it within 30 days. Therma-Tru gives its smooth fiberglass doors six months after installation, but says all edges of the door must be painted or stained within two weeks of installation or exposure to weather. Both makers tie their coverage to finishing on time.
A factory-finished door in good shape doesn't need paint. Painting makes sense for a color change, a worn finish, or an unfinished door that has to be finished.
Fiberglass or steel? Try a magnet
Not sure what you have? Pella's tip is to put a small magnet on the door. If it sticks, the door is most likely steel. The difference matters, because the two need different prep.
What kind of paint do you use on a fiberglass door?
An exterior paint made for doors, over whatever primer your door maker calls for. Therma-Tru's painting tips call for a high-quality acrylic latex house paint, exterior grade on outside surfaces. Clopay's older finishing sheet says most high-quality exterior acrylic latex or oil-based paints work on its fiberglass and steel doors.
Pella doesn't name a paint type. It asks for two coats of quality exterior paint with good blocking resistance, and says to have a paint professional recommend one.
Blocking resistance: the line most people skip
Blocking is fresh paint sticking to itself or to whatever presses against it. Pella warns that paint without good blocking resistance can leave a door that sticks shut even after the paint has dried. An entry door closes against weatherstrip every day, so this matters more here than on a wall. Our post on latex vs oil-based paint explains the two paint families.
What paint will adhere to fiberglass?
Paint grips fiberglass best over the right primer, and Dunn-Edwards, a paint maker, explains why it isn't always simple. Fire-retardant additives in some fiberglass doors cause outgassing, a slow release of volatile organic compounds. Once the door is primed and painted, those gases can build pressure behind the coating until it loses adhesion, blisters and peels.
Its advice: shade the door before you start so direct or even diffused sun stays off it, use fans to help drying and curing, prime with a bonding primer, and ideally give that primer 24 hours before the topcoat. It also recommends higher-sheen paints for added durability.
Where door makers disagree
Here's the part most painting guides skip. These are three door makers' own instructions, side by side. They don't match, so follow the finishing sheet for your door; all three of these makers post theirs online.
| Step | Pella | Therma-Tru | Clopay (2011 sheet) |
|---|---|---|---|
| Sanding | Fiberglass: don't sand. Steel: light 220-grit sanding | Not covered in its painting tips | Smooth doors: pre-sand with 600-grit |
| Weatherstrip | Leave it in place and tape it off | Pull it out before painting, put it back when dry | Don't paint the door sweep |
| Primer | Fiberglass: ask your paint supplier. Steel: factory-primed, no more needed | Prime wood-grained doors and lite frames | Not required on fiberglass |
| Time between coats | At least six hours | Follow the paint maker's directions | Follow the paint brand's drying time |
| Finish deadline | Within 30 days | Smooth fiberglass: six months. Door edges: two weeks | One month from purchase, before installation |
These are the makers' published instructions, not our recommendations. Therma-Tru's steel door sheet even gives two deadlines, several days in one spot and six months in another, so when in doubt, finish sooner.
Painting a steel door: factory primer and bare metal
Painting a steel door starts with the primer that's already on it. Pella says its steel doors are factory-primed and don't need more primer, but they do need prep: wipe the door with a solvent such as acetone or mineral spirits, let it dry until there's no odor, sand lightly with 220-grit paper, then wash with mild soapy water, rinse and dry. Two coats of exterior paint with good blocking resistance go on after that.
Bare spots change the rules. If sanding, a dent or a scrape gets through to bare metal, that metal may be galvanized, meaning zinc-coated. Dunn-Edwards says alkyd or oil-based primers must not be used on galvanized steel, because they react with the zinc and form a soap-like layer, a reaction called saponification. Over a fairly short period, sometimes weeks, it says the paint then peels.
Its fix is a high-performance acrylic bonding primer on any bare galvanized spot. For rust, dents and storm doors, see painting steel and other metal doors. Our post on painting a garage door covers galvanized steel in more detail.
Weather, sun and dark colors
Pella says to paint, stain or topcoat only when the temperature is between 50 and 90 degrees Fahrenheit and humidity is between 30 and 70 percent, and never in direct sunlight. Your paint's label may set its own range, so read both.
In southern Wisconsin that window closes for a good part of the year, and a mild fall afternoon can still turn into a cold night, so check the overnight low too. Our look at the Madison outdoor painting season covers the months that usually work.
Sun matters for a second reason on fiberglass. Dunn-Edwards says the sun's radiant energy heats the door and increases outgassing, which is why it recommends shading the door before you paint.
Dark colors behind a storm door
Pella says the combination of a darker color and direct sun can affect the door panel when a storm door is used. It recommends a ventilating storm door, with the screen in during summer if you have a fullview storm door. If you want a deep color on a sunny entry with a storm door, check your door maker's guidance first. Our post on front door colors has ideas for choosing one.
Next-step hurdle: a door that sticks or peels
The first problem after painting usually shows up when you close the door. Pella says to let the door dry completely, following the paint maker's directions, before closing it. Dry to the touch isn't the same as cured; our post on paint dry time vs cure time explains the gap.
Pella also says to finish every exposed edge of the door panel, including the top edge, because it helps reduce the chance of warping. It's the edge you can't see from the porch, so put it on your checklist.
Paint that lifts within weeks usually points back to prep: the cleaning, the primer, or on fiberglass, outgassing. Our guide on how to fix peeling paint walks through the repair.
When to stop and call a professional
- Call 911 if anyone has serious trouble breathing or passes out while working with solvents. Pella says to apply finishes only in a well-ventilated area.
- Today: if the frame, trim or an older steel door was painted before 1978, don't sand it until you know what's in the old paint.
- Stop if fresh paint won't stick, keeps blistering, or the door won't close properly after painting.
- Call a pro for a dented or rusting steel skin, a door that won't latch, glass that needs attention, or an unfinished door up against its maker's deadline.
If your home was built before 1978
EPA says old or worn lead-based paint, especially on surfaces that see constant friction like doors, can produce chips and dust that are hazardous when inhaled or swallowed. Its rule covers anyone paid to disturb painted surfaces in homes built before 1978, and Wisconsin is one of the states EPA authorized to run its own program.
Dunn-Edwards says fiberglass doors only became popular in the 1980s and 1990s, so in an older home the lead question is usually about the frame, the trim or an older steel door. Ask any painter how they handle lead-safe work practices, and see painting older Madison homes for more.
How we paint exterior doors at GK Painting
Exterior doors and entryways are part of our exterior work, along with garages and trim; we don't paint whole-house siding. We schedule smaller exterior projects around dry weather, and Wisconsin weather can shift the schedule.
Prep is some combination of cleaning, scraping, sanding, minor repairs and priming, because the finish is only as good as what's under it. We use premium paint from Sherwin-Williams and Behr, and Behr is the more economical of the two. If you'd rather use a brand you already like, just tell us and we'll use it.
George is on every job himself. We're based in Waunakee and work across Madison and the surrounding Dane County communities, and exterior work is priced with a written quote. The written quote is the price, no extra charge if the job takes longer than expected. Read about our exterior painting service or ask for a free estimate.
Common questions
What kind of paint do you use on a fiberglass door?
A quality exterior paint, usually acrylic latex, over the primer your door maker calls for. Therma-Tru's painting tips specify a high-quality acrylic latex house paint, and Pella asks for exterior paint with good blocking resistance so the door doesn't stick shut. Follow the finishing sheet for your own door, since makers differ.
Should a fiberglass door be painted?
If it came unfinished, yes, and on a schedule. Pella says its smooth fiberglass doors must be painted, within 30 days, and Therma-Tru gives its smooth doors six months but wants door edges finished within two weeks. A factory-finished door in good shape only needs paint when you want a new color.
What kind of paint will adhere to fiberglass?
Paint sticks best over a bonding primer on a clean surface. Dunn-Edwards recommends priming fiberglass doors with a bonding primer, letting it dry about 24 hours, then topcoating with a 100 percent acrylic or urethane-alkyd paint. It also says to shade the door, because sun heats fiberglass and increases outgassing.
Do you have to sand a fiberglass door before painting?
Only if your door's maker says to. Pella says not to sand its fiberglass doors, while Clopay's 2011 sheet suggests pre-sanding smooth doors with 600-grit paper. Clean the door either way, and follow the finishing sheet for your own door, because each maker ties its coverage to its own instructions.
Do you need to prime a steel door before painting?
Usually not the whole door. Pella says its steel doors come factory-primed and need cleaning, a light 220-grit sanding and a wash rather than more primer. Bare metal is different: Dunn-Edwards says galvanized steel needs an acrylic bonding primer and should never get an alkyd or oil-based one.
What temperature should it be to paint an exterior door?
Pella says to paint only between 50 and 90 degrees Fahrenheit, with humidity between 30 and 70 percent, and never in direct sunlight. Your paint's label may set its own range. In southern Wisconsin, check the overnight low too, since a mild afternoon can still turn into a cold night.
Sources
- Entry Doors: Fiberglass and Steel Owner's Manual, Pella
- Finishing Information, Therma-Tru Doors
- Finishing Instructions: Fiberglass and Steel Entry Door Systems (2011), Clopay Building Products
- Painting Fiberglass Doors (technical bulletin), Dunn-Edwards
- Lead Renovation, Repair and Painting Program, U.S. Environmental Protection Agency
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