In this article
- First, should this roof be painted at all?
- Know the factory finish you are painting over
- What type of paint to use on a metal roof
- Paint or roof coating: they are different jobs
- Prep decides how long the paint lasts
- Application: roller, brush or sprayer
- Color, heat and cool roofs
- Safety: who should be on the roof
- Pricing a metal roof painting job
- Frequently asked questions
Quick answer: For most painted or galvanized metal roofs, the best field paint is a 100 percent acrylic exterior latex made for metal, applied over a clean, degreased surface, with a rust inhibitive primer on any bare or rusted steel. Avoid oil or alkyd paint directly on galvanized metal, because the zinc reacts with it and the paint peels. If the roof needs waterproofing rather than color, you want a roof coating, not paint.
A metal roof is one of the few roofs you can repaint, which is why the question comes up so often. It is also a job where the product matters less than two earlier decisions: whether the roof should be painted at all, and what the metal surface is right now. This guide covers both, then the paint, the prep, color and heat, and when the job belongs with a roofer instead of a painter.
First, should this roof be painted at all?
Most modern metal roofs leave the factory with a baked on finish, and that finish is usually better than anything you can brush or spray on site. Before you buy paint, find out what is on the roof now.
- A sound factory finish that has faded or chalked. This is the common case. The panels still shed water and the finish is intact, it just looks tired. Painting is a cosmetic choice here, and a field coat will not outlast the factory coat it covers.
- A finish that has failed, with rust at laps, edges and fasteners. This is where painting earns its keep, because it protects metal that is now exposed.
- Bare galvanized or Galvalume panels, never painted. These can be painted, but each needs specific prep, covered below.
- A roof that leaks. Paint does not stop leaks. Fix the leak first, or look at a coating system designed for that job, which is covered in roof coating.
If the roof is still under the panel maker warranty, ask the maker before painting. Field painting changes the surface the warranty was written for, so it is worth a phone call before the work starts.
Know the factory finish you are painting over
Factory finishes on metal roofing fall into three broad families. McElroy Metal, a panel maker, describes them in its comparison of Kynar 500 and SMP finishes:
| Factory finish | What it is | How it ages |
|---|---|---|
| Polyester | The basic system. Hard and scratch resistant. | Prone to chalking, and the new gloss fades fairly quickly, according to McElroy. |
| Silicone modified polyester (SMP) | Polyester with silicone added to the resin. The most common mid range finish. | Better fade and chalk resistance than plain polyester, but below a PVDF system. |
| PVDF (sold as Kynar 500 and similar) | A fluoropolymer resin system. The premium finish. | The best fade, chalk and gloss retention of the three. |
Why this matters for painting: a chalky polyester roof is the most common candidate for a field coat, and the chalk has to come off first or the new paint sits on powder. A PVDF roof that still looks good is rarely worth painting. If you do paint over one, ask the paint maker which primer it approves for that finish before you start.
What type of paint to use on a metal roof
The default choice is a high quality 100 percent acrylic exterior latex rated for metal, often sold as direct to metal or DTM acrylic. There are good reasons it became the default:
- It works on galvanized metal. Sherwin-Williams says in its guidance on paint peeling from galvanized metal that most acrylic coatings adhere directly to clean galvanized metal.
- It works on Galvalume. A Fabral technical bulletin on painting Galvalume says exterior acrylic latex paints are the easiest to obtain and apply, and recommends them for most applications.
- It stays flexible. Metal roofs move a great deal between a cold night and a hot afternoon. Acrylic film moves with the panel instead of cracking.
What to avoid:
- Oil or alkyd paint directly on galvanized metal. Sherwin-Williams explains that alkyd paint will stick at first and then fail, because the zinc reacts with the alkyd binder and forms a soapy film under the paint. This is called saponification, and it is the classic reason paint sheets off a galvanized roof.
- Ordinary house paint not rated for metal. It may look fine for a season, but it lacks the adhesion and rust protection a roof needs.
- Bare paint over active rust. Any paint applied over loose rust fails with the rust.
For a wider look at metal in general, including railings, doors and siding, see best paint for metal.
Paint or roof coating: they are different jobs
People often use the words interchangeably, but they are different products for different problems.
| Roof paint | Roof coating | |
|---|---|---|
| Main job | Color and surface protection | Waterproofing and weather protection |
| Film | Thin, like house paint | Much thicker, often elastomeric, acrylic, silicone or polyurethane |
| Leaks | Does not fix them | Some systems are designed to seal seams and fasteners |
| Color choice | Wide | Usually white or a short list of light colors |
| Who applies it | Painters, or the owner on a safe roof | Often roofing or coating contractors |
If the roof is sound and the goal is a new color, paint is the right tool. If the roof has failing seams, rusted fasteners or a history of leaks, a coating system is usually the better answer, and the survey and prep for it are described in roof coating.
Prep decides how long the paint lasts
On a metal roof, almost every early failure traces back to the surface under the paint rather than the paint itself. The prep depends on what you found in the first step.
Faded or chalky factory finish
- Wash the roof to remove dirt and chalk. Rub a dark cloth on the dry surface afterward. If it still comes away white, wash again.
- Rinse thoroughly and let the panels dry completely.
- Check every fastener. Replace screws whose washers have cracked or gone hard, because paint will not seal them.
- Prime if the paint maker calls for it over an aged factory finish, then apply the acrylic topcoat.
New or bare galvanized metal
New galvanized sheet usually carries a light oil or a passivation treatment that stops paint from bonding, Sherwin-Williams notes. Weathered galvanized develops white rust, which must be removed. Its advice is to clean with a water based cleaner and degreaser rather than mineral spirits, because most hydrocarbon solvents leave a thin residue that causes paint to lose adhesion. Scrub off any white rust with a stiff brush or abrasive pad, rinse, and let it dry before painting.
Rusted steel
Remove loose rust and flaking paint with a wire brush or abrasive pad, feather the edges of sound paint, and spot prime the bare steel with a rust inhibitive metal primer before the topcoat. Pay special attention to the places rust starts on a roof: panel laps, cut edges, the drip edge and around fasteners. How to deal with peeling and rust on other metal is covered in how to remove paint from metal.
Weather
Paint on a dry day within the temperature and humidity limits on the can. Sherwin-Williams warns that painting new, oily or passivated metal in cold or humid conditions can lead to wrinkling and poor adhesion. A roof also gets far hotter than a wall in direct sun, so many painters start early and follow the shade. More on timing is in best weather conditions for exterior painting.
Application: roller, brush or sprayer
All three work. A sprayer is fastest on large, simple panels but needs calm air and careful masking, because overspray travels a long way from a roof. A roller with a nap suited to the panel profile is the common choice on ribbed or corrugated panels, with a brush to cut in along ribs, laps and trim. Apply the number of coats the paint maker specifies at the spread rate on the label rather than stretching one heavy coat.
Color, heat and cool roofs
Color on a metal roof is not only a look. Dark colors absorb more sun and run hotter, and light colors reflect more of it. ENERGY STAR explains on its cool roofs page that a cool roof uses a material or coating that reflects sunlight and lowers the roof surface temperature, that metal is one of the common cool roof materials, and that cool roofs save the most energy in hot, sunny climates.
In practice:
- In a hot climate, a light color or a reflective coating can make the space under the roof more comfortable.
- In a cold climate, the cooling benefit is smaller, so color is mostly a matter of looks.
- Dark colors on metal show chalk and fading sooner, so the factory finish comparison above matters more for a black or dark bronze roof.
For help choosing a palette that works with the rest of the house, see how to choose exterior paint colors.
Safety: who should be on the roof
A metal roof is slippery, especially when it is wet, dusty or freshly painted, and a fall from any roof can be serious. Low slope outbuilding roofs are often workable with proper fall protection. Steep or high roofs, and any roof over an occupied home, are usually better handled by a contractor with the right access equipment and insurance. Never stand on wet paint or walk panels between the ribs where the metal flexes.
Pricing a metal roof painting job
For painters, metal roofs price differently from walls. Washing, rust treatment and fastener replacement can take longer than the painting itself, access equipment is a real cost, and roofs are measured by the actual panel area including the profile, not the flat footprint. A detailed breakdown of measuring, access and prep on metal structures is in how to price painting metal buildings.
Frequently asked questions
What is the best paint for a metal roof?
For most roofs, a high quality 100 percent acrylic exterior latex rated for metal, applied over a clean, dry, degreased surface. Spot prime bare or rusted steel with a rust inhibitive primer first. Follow the paint maker on primer and coats for your specific roof.
Can you paint a galvanized metal roof?
Yes. Clean off any oil, passivation residue and white rust with a water based degreaser and a stiff brush, then use an acrylic paint. Do not use oil or alkyd paint directly on galvanized metal, because the zinc reacts with it and the paint peels.
Is a roof coating better than paint?
They do different jobs. Paint changes color and protects a sound surface. A roof coating builds a much thicker film and is chosen when the roof needs weather protection, sealing at seams and fasteners, or a reflective surface. Neither replaces a repair on a roof that leaks.
Should I paint a factory finished metal roof?
Only if the finish has failed or you want a different color. A sound factory finish, especially a PVDF finish, usually outlasts a field coat. If the roof is under warranty, ask the panel maker before painting.
Does a light colored metal roof keep a house cooler?
It can. A light or reflective finish lowers the roof surface temperature, and ENERGY STAR says cool roofs save the most energy in hot, sunny climates. The benefit is smaller in cold climates.
Can I paint a metal roof with a roller?
Yes. A roller with a nap that suits the panel profile is a common choice, with a brush for ribs, laps and trim. Spraying is faster on large roofs but needs calm air and careful masking.
