Roofing
Metal roof restoration and coating field guide
Renewing an aging, rusting metal roof in place: qualifying the roof, treating the rust, fixing the leaking fasteners and seams, and coating it, instead of a tear-off.
Direct answer
Metal roof restoration renews an aging, rusting metal roof in place by treating the rust, repairing the backed-out fasteners and the leaking seams, and coating the whole roof, instead of a tear-off. It fits a roof that is structurally sound but corroding, not one rusted through. The coating manufacturer's system governs the prep, the primer, and the mils.
Key takeaways
- Metal roof restoration treats rust, repairs fasteners and seams, then coats the roof in place, buying 10 to 20 years versus a tear-off.
- A roof qualifies only if structurally sound with surface rust; metal rusted through, perforated, or with fasteners that no longer hold is a replacement.
- Stop rust before coating: wire-brush to sound metal, apply a phosphoric-acid rust converter, then a rust-inhibitive primer (often around 200 sq ft per gallon per coat).
- Drive, upsize, or cap every backed-out or wallowed fastener; a common move upsizes #12 screws to #14 with an EPDM washer.
- The coating manufacturer's published system and warranty for metal substrates governs the prep, primer, dry mils, and approved applicator.
Metal roof restoration, and where it fits
Metal roof restoration is the renewal of an aging metal roof in place: you stop the rust, fix the fasteners and the seams that leak, and coat the whole roof, instead of tearing it off. It buys 10 to 20 years on a roof that still has sound metal under the corrosion, at a fraction of the cost and the disruption of a replacement. The roof keeps the building dry under you while you do the work.
Where it fits is narrow, and worth being honest about. Restoration renews a roof that is structurally sound but rusting and leaking at the details. It does not rebuild a roof that has rusted through, lost its structure, or perforated across the field. A coating is a surface system, not a structural repair, so the metal under it has to carry the load and still hold a fastener.
Two siblings sit next to this work. When the metal is too far gone, the answer is a new roof, and the panels, clips, seams, and slope limits are covered in the standing seam metal roof installation guide. The coating chemistry itself, the silicone and acrylic and urethane and how each one cures, is worked end to end in the roof coating restoration system guide. This guide is the metal-specific version: the rust, the fasteners, the seams, and what the coating has to survive on a metal roof that the membrane roofs never put it through.
Is my metal roof a candidate for restoration?
A metal roof is a candidate for restoration when the panels are structurally sound and the rust is on the surface, not through it. It is not a candidate once the metal has rusted through, the fasteners no longer hold in their holes, or the panels need replacing across the field. The qualifying call is whether the metal can still carry the load and bite a fastener, because the coating protects what is there. It cannot rebuild it.
Walk it before you bid it. Surface rust that wire-brushes back to sound, tight metal is fine. Rust that has eaten holes through the panel, perforation, is a replacement, and most panel warranties treat perforation as the end of the panel's life for a reason. Soft or flapping panels, fasteners you can pull out by hand, and a deck or purlin that has corroded at the bearing are all past restoration. Sound the suspect areas underfoot and probe the rust with a screwdriver. If it goes through, that panel is gone.
The blunt version: a coating does not fix a perforated roof. Coat over metal that is rusted through and you have spent good money sealing the top of a roof that is failing from the inside. The rule that holds up in the field is the same one the membrane restoration uses. If a small share of the roof is gone, you replace those panels and restore the rest. If most of it is gone, replace the roof and put the coating money toward the new one.
Why does my metal roof leak at the screws?
An exposed-fastener metal roof leaks at the screws because every screw is a hole through the panel sealed only by a rubber washer, and that washer is the first thing to fail. The panel expands and contracts with every hot day and cold night, and that movement works each screw in its hole for years. The gasket hardens, cracks, and loses its grip. The screw backs out a little. The hole wallows out oversized. Now wind-driven rain has a path straight through the roof, and there are hundreds to thousands of these holes on a single roof.
This is the most common metal roof leak, and the trade knows it cold: the screws and the washers are the leak, not the field of the panel. Overdriving the screws at install makes it worse, because crushing the washer cracks or cups it on day one and starts the same leak years early.
The fix on restoration is to address every fastener before the coating. A screw that has backed out and still seats gets driven home. A screw in a wallowed hole gets pulled and replaced with the next size up, an oversized fastener with a fresh gasketed washer, so the larger shank bites fresh metal or wood instead of spinning in the old hole. A common move is to upsize the whole field from a #12 to a #14 with an integrated EPDM washer where the originals have wallowed. Where a hole is too far gone for even an upsize, it gets a butyl cap or a reinforced patch in the coating. A fastener you leave loose is an open hole under the film, and a coating alone will not bridge a moving screw head for long.
How do you treat rust on a metal roof?
You stop the rust before any coating goes on, because active rust keeps spreading under a sealed film and lifts it off. The sequence is mechanical first, chemical second, primer third. Knock the loose scale and flaking rust off with a wire brush, a wire wheel, or on a heavily corroded roof a power tool or an abrasive blast, back to sound, tight metal. A coating bonded to loose scale peels with the scale, and no chemistry saves it.
Then the chemistry. On lightly to moderately rusted metal, a rust converter, a phosphoric-acid product, turns the flaky iron oxide into a stable iron phosphate that the primer can bond to and that does not keep shedding. A rust-inhibitive primer goes over the cleaned, converted metal to lock in what remains and put a zinc-phosphate or equivalent barrier between the steel and the weather. Many of these primers want two coats and call out a coverage rate, commonly around 200 sq ft per gallon per coat, so pull the number off the actual product.
The thing rookies get wrong is the spot prime versus the full prime. Where rust is scattered, you spot-treat and spot-prime the rusted areas and the staining keeps coming back at the spots you missed. On a roof that is rusting generally, the whole field gets primed, not just the visible rust, because the rust you can see is ahead of the rust you cannot. The coating manufacturer's system tells you which primer over which metal, and the rust treatment is the part of a metal restoration that has no equivalent on a membrane roof.
Sealing the seams and the laps
The seams and the end laps are where the panels move the most and where water already gets in, so they get detailed before the field coat, not painted over with it. On an exposed-fastener roof the side laps and the eave-to-ridge end laps open and close with thermal movement, and the original lap sealant has usually dried hard and pulled away. On a standing seam roof the seams ride above the water, but the old in-seam sealant and the flashing laps still age out.
The detail is a sealant plus a reinforcement, the same three-course idea the membrane restoration uses, sized for metal. A butyl seam tape, a polyester-reinforced butyl rubber tape, gets pressed over the cleaned lap to seal the joint, and because butyl degrades in sunlight it has to be top-coated, never left exposed. Over the more active seams and along the fastener rows, polyester reinforcing fabric is embedded in the coating: a base coat, the fabric broomed in while wet so the coating wets through the weave, then a top coat that locks it in. The fabric carries the tensile load where the metal moves and a plain film alone would split.
The full reinforcement chemistry and the three-course mil build are worked in the roof coating restoration system guide. On metal the rule is the same as everywhere else. Fix and reinforce the joint that moves before you stretch a film across it, because the film tears where the metal works, every time.
Cleaning the roof so the coating bonds
A coating bonds to clean metal, not to the chalk, oil, and grime on top of it, so the wash is part of the system and not a courtesy. A metal roof carries its own contaminants: chalk from the old factory paint breaking down, mill oil and traffic grease, dirt packed in the rib valleys, and biological growth on the shaded slopes. Coat over any of it and the film sticks to the contaminant instead of the panel and peels, usually at an edge within a year.
The sequence is the manufacturer's cleaner, a power wash, and a full rinse and dry, the same prep the membrane restoration spells out in detail. On metal, chalk is the one that fools people, because a chalked panel looks like a faded panel, not a dirty one. Rub it with a dark cloth. If it comes away white, the surface is letting go, and the wash has to take the chalk off or the coating bonds to a layer that is already failing.
After the wash, the metal has to dry through before primer, and an adhesion test patch confirms the bond before the field coat. The prep and the adhesion test are common to all coating work, so this guide points to the roof coating restoration system guide for the deep version and stays on what is metal-specific.
The coating system over metal
The field coat over a metal roof is usually silicone or a rubber-modified solvent coating, chosen because metal moves hard with temperature and the film has to flex with it without cracking. Silicone leads where the roof weathers hard and where any low-slope area ponds, because it shrugs off standing water and UV and holds its reflectance. SEBS and other rubber-modified coatings stay flexible in cold and bond well to metal, which is why they show up on metal roofs in cold climates. Acrylic is the bright, low-cost cool-roof option on a sloped metal roof that drains and never ponds, but it softens under standing water, so it is the wrong call at a dead-flat eave detail or a ponding valley.
Which chemistry, at what mils, and how the gallons are figured is the work of the roof coating restoration system guide, and the chemistry does not change because the substrate is metal. What changes is the order of operations under it. On metal the rust is stopped, the fasteners are tightened or upsized, and the seams are reinforced first, and only then does the field coat go on over a primed, sound surface.
The coating manufacturer's published system for metal substrates governs the primer, the dry mils, and the warranty. A coating over live rust or a loose screw is a coating with a built-in lift-off date, no matter how good the chemistry is.
Does a coating make a metal roof cooler?
Yes, a reflective coating drops the surface temperature and the cooling load on a metal roof, and the gain is bigger on metal than people expect. Bare and dark-painted metal is a good solar reflector but a poor thermal emitter, so it gets hot in the sun and holds the heat, and a dark metal roof can run 50 to 90 degrees F above air temperature on a clear afternoon. A white reflective coating bounces most of the sun back, commonly reflecting 80 to 90 percent of solar energy, so the roof runs far cooler and so does the building under it.
That energy benefit rides on three numbers, the same ones the membrane cool-roof work uses: solar reflectance, thermal emittance, and the combined solar reflectance index. Where it turns into money or a requirement is the energy code in hot climates, California's Title 24 the common example, and the utility rebate programs, which often turn on the coated roof meeting a reflectance or SRI threshold and being listed by a rating body. Confirm the cool-roof requirement against the adopted energy code and the specific product, because the reflectance qualification is separate from the waterproofing spec and the warranty.
One field note that matters on metal: reflectance drops as the roof picks up dirt, so the aged number, not the day-one number, is what the energy benefit runs on over the years. A dirty white roof is a less reflective roof.
Restoring a standing seam vs an exposed-fastener roof
The restoration changes with the panel, because the two metal roof types fail in different places. An exposed-fastener, or through-fastener, roof is screwed straight through the panel face, so its leaks are at the screws and the end laps, and the restoration is mostly fastener work: tighten, upsize, or cap every screw, seal the laps, treat the rust, then coat. On an exposed-fastener roof the fasteners are the whole job.
A standing seam roof carries no fasteners through the weather surface, because the panels ride on concealed clips and the seams stand above the water. So its restoration is different. There are no field screws to chase, and the work moves to the seams, the flashings, the penetrations, and any rust at the panel edges and the closures. A standing seam roof rarely needs a coating to stop screw leaks, because it never had screw leaks. It gets coated for reflectance, for a weathered finish, or for aging seam and flashing sealant.
The new-roof side of this, what standing seam and exposed-fastener panels are and why the concealed-clip roof outlasts the screw-down two to one, is covered in the standing seam metal roof installation guide. For restoration the takeaway is to size the scope to the panel: an exposed-fastener roof is a fastener-and-rust job, and a standing seam roof is a seam-and-flashing job.
Spray foam over an old metal roof
Spray polyurethane foam is the other way to renew a metal roof, and it is a different system from a coating, not a competitor in the same lane. Closed-cell SPF is sprayed over the cleaned, prepared metal, where it self-flashes around the seams, the fasteners, and the penetrations in one monolithic pass, fills the rib voids, adds real R-value, and stops the panel flutter. A coating then goes over the foam to protect it from UV. On a metal building that is also losing energy through an under-insulated roof, the foam solves the insulation and the leaks at once, and adding a few inches of closed-cell foam over the existing assembly can lift the roof well up the R-value scale.
The catch is the same as any metal restoration. The rust still has to be stopped and the metal sound before the foam goes on, because foam over live rust traps the corrosion against the panel where you can never see it again. SPF is its own trade with its own application and QC, so this guide flags it by topic rather than working it in depth.
The decision between a coating restoration and an SPF restoration usually comes down to whether the building needs the insulation and the rib-fill the foam adds, or just the watertight, reflective surface a coating gives.
Recovering with new metal over the old
When the existing metal roof is too tired to coat but the building cannot take a tear-off, a metal-over-metal recover puts a new roof over the old one without stripping it. Retrofit sub-purlins, sometimes called hat channels or notched zee sub-purlins, nest over the ribs of the existing panels and fasten through to the structural purlins below, creating a new, level plane to carry a new standing seam or exposed-fastener roof above the old one. The notched sub-purlin gives a structure-to-structure connection with the least added height, and the cavity between the two roofs can be filled with insulation or left as a ventilated air space.
This is a re-roof, not a restoration, so it belongs to the new-roof side of the work, and the new panel above it follows the standing seam metal roof installation guide. It earns its place in a restoration discussion because it is the honest answer when the candidate inspection comes back too far gone for a coating but the owner needs the building to keep running.
The old roof stays as a deck and a vapor layer, the new metal does the work, and the structural check on whether the existing purlins can carry the added load is the part that is engineered, not assumed.
The restoration warranty and the renewable re-coat
The warranty on a metal restoration is the manufacturer's, and on a coating it is tied to the dry mils, the prep, and an approved applicator, the same as any coating system. More mils buy more years on the manufacturer's ladder, commonly landing a metal restoration in the 10 to 20 year range depending on the system, and the warranty is released by a closeout inspection that checks the rust treatment, the fasteners, the seam reinforcement, and the mils across the roof. A roof that reads light on the gauge fails the inspection no matter how good it looks from the ground.
The renewable part is what makes restoration pay over the long run. At the end of the term a sound coated metal roof can usually be cleaned and re-coated to renew the system and the warranty again, without a tear-off, as long as the new coat is compatible with the old, which for silicone means silicone over silicone. Read the warranty document for what it actually requires: the primer, the mils, who may apply it, and the maintenance that keeps it in force.
The metal-specific catch is that the warranty assumes the rust was stopped and the fasteners were sound at the start. So the prep record on the rust and the fasteners is part of what defends a claim years out, not just the mil log.
Quality control on a metal restoration
Quality control on a metal restoration happens while the crew is on the roof, because the rust treatment, the fastener work, and the dry mils all cure in invisible the day after they leave. Five checks carry the metal job, and the first three are the ones a membrane roof does not have.
The rust check: every rusted area was wire-brushed to sound metal, converted where called for, and primed, with no loose scale left under the coating. The fastener check: every backed-out or wallowed screw was driven, upsized, or capped, with no loose head left to telegraph through the film. The seam check: the laps and seams were sealed and reinforced, with the fabric fully encapsulated, no dry threads and no bridging. Then the two checks common to all coating work: the adhesion test patch pulled and held before the field coat, and the wet mils read on a notched gauge across a grid so the dry mils land where the warranty wants them, confirmed after cure.
Tie every reading and every repair to a place on the roof. A mil log with no locations is a log nobody can act on, and over a metal roof the rust and fastener record is exactly what the warranty inspection runs against.
Restoring the metal roof over a critical building
On a metal building that cannot go offline, a distribution center, a manufacturing plant, or a data hall under a metal deck, restoration earns its keep because it renews the roof without opening the building to weather. The acres of exposed-fastener or standing seam metal over an operating facility are exactly the roofs where a tear-off is the expensive, disruptive option and a coating or an SPF restoration keeps the operation running underneath.
What changes over a critical space is the tolerance for a miss. A leak over a data white space or a packed warehouse aisle is not a stained ceiling tile, it is downtime or damaged stock, so the fastener work and the seam reinforcement directly over the critical zone are held tighter and the QC on the mils is closer there. The application also has to respect the operation below: no overspray drift into rooftop intakes, no solvent fumes drawn into the building, and tight control of foot traffic and dropped tools during the work.
A roof this size gets phased in sections coordinated with the operation and the weather window, each section carrying its own rust, fastener, seam, and mil record, because over a building measured in uptime the roof file is part of the risk record, not an afterthought.
The maintenance the owner takes on
A restored metal roof is still a metal roof, and it earns its full life only on a maintenance program. The coating renews the surface. It does not relieve the owner of the same spring-and-fall plus post-storm walk every roof needs, and on metal that walk has its own short list. Watch the fasteners on an exposed-fastener roof, because thermal cycling keeps working them and a screw can back out under the coating over time. Watch the seams and the laps for any spot where the reinforcement is showing or the sealant has moved. Watch for new rust at a scratch, a dropped tool, or an edge where the coating wore thin, because bare metal rusts and the rust spreads under the film.
Caught early, a worn or scratched area is a clean-and-spot-coat patch and a fastener is a five-minute fix. Ignored, the rust is back under the coating and the leak is back at the screw, and the restoration ages as fast as the roof it replaced.
Plan the renewable re-coat as a scheduled capital item toward the end of the warranty term, on the condition data the maintenance walk produces, not as the emergency the year it starts leaking again.
What to document
The record on a metal restoration proves the rust was stopped and the fasteners and seams were fixed before the coating sealed everything in, and it is the difference between a paid warranty claim and a denied one years out. Document by area as you work, so a reading and a repair tie to a place on the roof.
Capture the section of roof, the rust condition and the treatment done, the fastener work, the seam and lap detail, the primer applied, the coating chemistry and the target dry mils, the wet mils read on the grid, and the weather at application. The fastener and rust records are the metal-specific ones the membrane restoration does not need, and they are the first thing a warranty inspector asks for when a metal roof claims a leak. A tool like FieldOS is built to hold exactly this kind of by-area record, photos, readings, and repairs tied to a place, so the file is the one the warranty inspection runs against.
| Area | Rust / fastener | Seam | Primer | Coating / mils |
|---|---|---|---|---|
| South exposed-fastener slope | Surface rust wire-brushed; #12 screws upsized to #14 with EPDM | Butyl tape plus fabric at end laps | Rust-inhibitive primer, 2 coats | Silicone, 25 dry mils, 2 coats |
| North shaded slope | Chalk and growth washed; scattered rust spot-primed | Fabric at side laps and fastener rows | Rust-inhibitive primer, spot | Silicone, 25 dry mils |
| Low-slope eave / ponding strip | Sound, no rust | Fabric at seams | Bonding primer per data sheet | Silicone, 40 dry mils |
| Standing seam field | Edge rust at closures cleaned | Fabric at seams, flashing laps re-sealed | Per system for the finish | Acrylic cool-roof, 2 coats |
Common mistakes
- Coating over live rust with no wire-brush or rust-inhibitive primer, so the corrosion spreads under the film and lifts it.
- Coating over backed-out or wallowed fasteners, so the roof still leaks at the screws under a fresh warranty.
- Sealing nothing at the seams and laps, so the film tears where the panels move the first hot-cold cycle.
- Skipping the wash and the adhesion test, so the coating bonds to chalk or oil and peels at the edges within a year.
- Putting acrylic on a metal roof that ponds at the eave or in a valley, where a water-based film softens and breaks down.
- Coating a roof that has rusted through or perforated, sealing the top of a roof that is failing from the inside.
- Upsizing fasteners but spinning the new screw in a hole too far gone to bite, instead of capping or patching it.
- Spot-treating only the visible rust on a generally rusting roof and leaving the rust you could not see to come back.
Field checklist
Want this checklist to run itself on every job — with photo proof and a signed record crews can hand the customer? That's FieldOS.
Standards and references
The document that governs a metal restoration is the coating manufacturer's published system and warranty for metal substrates, full stop. It sets the approved metals, the rust treatment and primer, the seam and fastener details, the target dry film thickness tied to the warranty term, and who may apply it, and the closeout inspection runs against it. Confirm every specific against the actual product, because the system for one coating does not carry to another.
Around that, a few bodies set the framework. The Metal Construction Association, the MCA, publishes guidance on metal roof systems, retrofit, and corrosion. The NRCA covers low-slope and metal roofing practice generally. The ASTM material specifications define what each coating and primer has to be, with the silicone, acrylic, and other chemistries falling in the ASTM D08 roofing family and some designations revised or withdrawn across the cycles, so confirm the current one before citing it. The Roof Coatings Manufacturers Association, the RCMA, publishes technical guidance on the use of primers and on application conditions including the dew-point margin.
The cool-roof and energy side intersects through the adopted energy code, California's Title 24 the common example, and the reflectance rating programs, which are a separate check from the waterproofing spec. Through all of it the project specifications and the adopted code edition with local amendments control, and the manufacturer's warranty overrides any rule of thumb on the rust treatment, the fasteners, the primer, and the mils. Never invent a section number. Cite a standard by name and topic and verify the designation against the current edition.
Units, terms, and references
A metal restoration reads across a data sheet, a spec, and a warranty, and the same idea shows up under different names, so a short glossary keeps the crew and the inspector on the same word.
Thickness is in mils, one mil being one thousandth of an inch, about 25.4 microns. Coverage is in square feet per gallon or gallons per square, a square being 100 square feet of roof. Gauge describes the panel steel thickness, where a higher number is thinner metal. Reflectivity shows up as solar reflectance, thermal emittance, and the combined SRI. Fasteners are sized by a number, a #12 or a #14, where the larger number is the larger diameter. The terms below are the ones specific to a metal restoration.
- Metal roof restoration
- Renewing an aging metal roof in place by treating rust, repairing fasteners and seams, and coating it, instead of a tear-off
- Exposed / through-fastener panel
- A metal panel screwed through its face, where the screws and their rubber washers are the common leak
- Rust converter
- A phosphoric-acid product that turns flaky iron oxide into a stable iron phosphate the primer can bond to
- Rust-inhibitive primer
- A primer, often zinc-phosphate based, that binds remaining rust and blocks moisture before the coating
- Butyl seam tape
- A polyester-reinforced butyl rubber tape that seals a lap or seam and must be top-coated, never left exposed
- Fastener upsize
- Replacing a wallowed screw with the next larger diameter and a fresh gasketed washer so it bites fresh metal
- Reinforcement fabric
- Polyester fabric embedded in the coating at seams, laps, and fastener rows for tensile strength and crack-bridging
- SRI / cool roof
- Solar reflectance index, the combined reflectance and emittance rating energy codes and rebates use for reflective roofs
FAQ
How do you restore a metal roof?
You restore a metal roof by treating the rust, repairing the fasteners and seams, and coating it, in that order. Wire-brush and prime the rust, drive or upsize the backed-out screws, seal and reinforce the seams and laps, wash the roof, then apply the coating to the warranted dry mils. The metal has to be structurally sound first.
Can you coat a rusty metal roof?
Yes, as long as the rust is on the surface and the panels are sound, not rusted through. Knock the loose scale off with a wire brush, treat it with a rust converter where needed, and prime with a rust-inhibitive primer before the coating. Coating over live rust just traps it and lifts the film.
Why does my metal roof leak at the screws?
An exposed-fastener metal roof leaks at the screws because each screw is a hole sealed by a rubber washer that ages out. Thermal movement works the screw in its hole, the washer cracks, the screw backs out, and the hole wallows oversized. Overdriving the screws at install cracks the washer and starts the same leak years early.
What coating goes on a metal roof?
Silicone and rubber-modified SEBS coatings are the common choice on metal, because they flex with the metal's thermal movement and silicone tolerates ponding. Acrylic is the low-cost reflective option on a metal roof that drains and never ponds. The coating manufacturer's system for metal substrates sets the primer, the dry mils, and the warranty.
When should you replace a metal roof instead of coating it?
Replace a metal roof when the panels have rusted through or perforated, the fasteners no longer hold, or the deck or purlins have corroded at the bearing. A coating is a surface system, not a structural repair, so it cannot rebuild metal that is gone. If a small share is failed, replace those panels and restore the rest.
How do you fix backed-out screws on a metal roof?
Drive a screw that still seats home, but a screw in a wallowed, oversized hole gets pulled and replaced with the next larger diameter and a fresh gasketed washer so it bites fresh metal. A common move is upsizing a #12 to a #14 with an integrated EPDM washer. Holes too far gone get a butyl cap or a patch.
Does a roof coating make a metal roof cooler?
Yes. Dark and bare metal heats up in the sun and holds the heat, often running 50 to 90 degrees F above air temperature. A white reflective coating bounces 80 to 90 percent of the solar energy back, dropping the surface temperature and the cooling load. Confirm any cool-roof or rebate qualification against the energy code and the product.
How long does a metal roof restoration last?
A warranted metal restoration commonly carries a manufacturer's warranty in the 10 to 20 year range, tied to the dry film thickness, with more mils buying more years. It is renewable: toward the end of the term a sound coated roof can be washed and re-coated to renew the system, with silicone re-coating only with silicone.
Should you reinforce the seams when coating a metal roof?
Yes. The seams and end laps move the most and leak first, so they get a butyl seam tape and polyester reinforcing fabric embedded in the coating before the field coat. The fabric carries the tensile load where the metal works, so the film does not tear there. Butyl must be top-coated, because sunlight degrades it.
People also ask
Codes cited in this guide
This guide is written and reviewed against the published standards below. Always confirm the current adopted edition with the authority having jurisdiction.