By The Roofing Brief Team. Last reviewed: October 2026.
Metal roof coatings are liquid-applied, fully adhered membranes rolled or sprayed over an existing metal roof to stop leaks, block corrosion and reflect heat, for roughly $0.50 to $4.00 per square foot installed according to HomeGuide’s roof coating cost guide (April 2024), instead of a full tear-off. Warranty length is bought with film thickness: Uniflex’s silicone system for structural metal roofing calls for 1.5 gallons per 100 sq ft (22 mils dry) for a 10-year warranty and 2 gallons (30 mils dry) for 15 years. The chemistry only works if it bonds to your specific metal, and a metal roof fails at cut edges, fasteners and seams long before the flat of the panel does.
What are metal roof coatings and what do they actually do?
A metal roof coating is a fluid-applied elastomeric layer that cures into a continuous, waterproof membrane bonded directly to steel, aluminum or Galvalume panels. It restores a weathered roof rather than replacing it: sealing pinhole leaks, encapsulating surface rust and adding a reflective surface. Henry’s 887 Tropi-Cool silicone, for example, is CRRC-rated (product ID 0620-0051) at 0.88 initial and 0.73 aged solar reflectance, per its technical data sheet.
Coatings buy time on a roof that is watertight in structure but failing at the surface. They will not save a panel that has rusted through, and they do not add structural strength: the Uniflex spec requires damaged, weakened or corroded panels to be replaced, and panel laps open more than 1/8 inch to be refastened, before any coating goes down. On a metal roof the fasteners, overlaps and cut edges fail first, so the system depends on how well those details are sealed before the field coat.
Types of metal roof coatings compared
Four coating chemistries dominate metal roofs: acrylic, silicone, polyurethane and aluminum-pigmented asphaltic. Each has its own ASTM product standard: ASTM D6083 for acrylic, ASTM D6694 for silicone and ASTM D6947 for polyurethane (both written for foam roofing but cited on metal-coating data sheets), and ASTM D2824 for aluminum-pigmented asphalt. Installed prices below are HomeGuide’s; specs come from the named data sheets.
| Coating | Installed cost / sq ft (HomeGuide) | Example product spec | Water behavior | Best fit on metal | Source |
|---|---|---|---|---|---|
| Acrylic (water-based elastomeric) | $0.50 to $3.00 | Henry 587 Dura-Brite: 47 to 51% solids by volume, about 1 gal per 100 sq ft in two coats, solar reflectance 0.84 | Water-based; no rain, dew or temperatures under 50°F within 48 to 72 hours of application | Sloped metal in dry, sunny climates on a budget | Henry 587 TDS |
| Silicone (high-solids) | $1.50 to $4.50 | Henry 887: 91% solids by volume, 1.5 gal per 100 sq ft, 22 mils dry minimum; Rust-Oleum 995: 95.5% solids by volume, 24 mils dry | Henry rates 887 for permanent ponding water resistance; rain-safe in 15 minutes | Low-slope metal, humid or ponding-prone roofs | Henry 887 TDS; Rust-Oleum 995 TDS |
| Polyurethane | $1.50 to $4.00 | Moisture-cured products specified to ASTM D6947 | Water-resistant, abrasion-tough | Roofs with foot traffic or rooftop equipment | HomeGuide; ASTM |
| Aluminum-pigmented asphaltic | $1.00 to $2.50 (HomeGuide bitumen row) | Products specified to ASTM D2824 | Water-shedding | Older galvanized barns and outbuildings | HomeGuide; ASTM |
Solids content is the number that explains most of the price gap. One gallon spread over 100 sq ft lays down about 16 wet mils. At Henry 587’s 47 to 51% solids, a 1-gallon two-coat application leaves roughly 7.5 to 8.2 dry mils; at Henry 887’s 91% solids, the 1.5-gallon rate leaves about 22 dry mils, which is the figure Henry prints. Silicone also stays flexible through the daily expansion of metal panels: Henry lists 280% minimum elongation for 887 and Rust-Oleum lists 150% for 995.
Which coating bonds to your metal? The substrate rule that traps owners
Adhesion is decided by what is already on the panel, not by which coating is cheapest. Rust-Oleum’s 995 data sheet says bare galvanized metal with no rust needs no primer, but bare steel and any rusty or corroded metal must be cleaned and primed with Rust-Oleum 115 Hybrid Epoxy Primer. Henry’s 587 sheet calls for its 107 asphalt emulsion sealer first on previously uncoated metal. A factory Kynar (PVDF) finish is slick and usually needs scuffing plus a compatible primer and an adhesion test.
The trap few buyers are warned about is silicone re-coat lock-in. Acrylic and paint do not bond to cured silicone, so once a roof is silicone-coated, future recoats are silicone. The Henry 887 limited warranty is void if the coating is coated over or patched with any product other than 887 or approved products. Rust-Oleum lists existing silicone as an approved substrate for 995. Confirm the primer and topcoat against the maker’s data sheet for your exact panel finish before a drop goes on the roof.
Coating a metal roof is different from painting one. If your goal is color change on sound panels rather than waterproofing, see whether you can paint a metal roof instead, because paint and elastomeric coatings solve different problems. Factory paint is thin: the Metal Sales PVDF spec totals 0.90 to 1.10 mils dry, against 22 to 30 mils for the silicone systems above.
How much does it cost to coat a metal roof?
Coating a metal roof runs about $0.50 to $4.00 per square foot installed, according to HomeGuide (April 2024), so a 2,000 square foot roof lands roughly between $1,000 and $8,000. HomeGuide names rust condition, repairs and roof access as what moves the price. Silicone sits at $1.50 to $4.50 installed, polyurethane at $1.50 to $4.00 and acrylic at $0.50 to $3.00 in the same guide.
| Worked example: 2,000 sq ft metal roof | Material quantity | Installed cost range | Source |
|---|---|---|---|
| Silicone, 10-year spec (1.5 gal / 100 sq ft) | 30 gallons | $3,000 to $9,000 at $1.50 to $4.50 / sq ft | Uniflex spec; HomeGuide |
| Silicone, 15-year spec (2 gal / 100 sq ft) | 40 gallons | Same HomeGuide range; expect the upper half for the thicker film | Uniflex spec; HomeGuide |
| Acrylic, two coats (about 1 gal / 100 sq ft) | About 20 gallons | $1,000 to $6,000 at $0.50 to $3.00 / sq ft | Henry 587 TDS; HomeGuide |
Compare a coating against replacement on cost per year of dry service: divide the installed price by the warranty years the coating maker will actually issue for your roof, and do the same for a reroof quote. For example, a $6,000 silicone job carrying a 15-year Uniflex warranty works out to $400 per warranted year. Compare any coating bid with the price of a new roof in our metal roof cost guide. For line-item prices and data-sheet material math, see our itemized metal roof painting and coating cost guide. For a full comparison of chemistries and pricing across all roof types, see our breakdown of roof coating types and cost.
How is a metal roof coating applied? The prep decides the result
A metal roof coating is applied in a fixed sequence where surface prep and detail sealing carry most of the labor. The steps below follow the Uniflex structural-metal spec and the Henry and Rust-Oleum data sheets; your coating maker’s sheet governs if it differs.
- Inspect and repair. Replace rusted-through panels, replace damaged fasteners and tighten the rest to the panel maker’s spec, and fasten any lap open more than 1/8 inch (Uniflex). A coating cannot bridge a structural hole.
- Power wash. Wash with a power washer over 2,000 psi, treat algae or mildew with trisodium phosphate (TSP) or a non-filming detergent, and rinse clear (Uniflex). Let the roof dry fully.
- Treat rust and prime. Wire-brush rust (Henry 887 sheet), then prime corroded areas with a rust-inhibitive primer such as Uniflex 34-520 or Rust-Oleum 115 and let it cure.
- Seal the details. On through-fastened laps, Uniflex calls for 16 wet mils of silicone extending 2 inches each side of the seam, and sealant 1/16 inch thick (60 wet mils) extending 3 inches around curbs and penetrations.
- Apply the field coat. Roll with a 3/4-inch nap or spray airless to the warranty rate, for example 1.5 or 2 gallons per 100 sq ft of Uniflex silicone, checking with a wet mil gauge. Work only at 40°F and rising with roof surfaces between 40°F and 140°F (Uniflex); Rust-Oleum says not to apply 995 if rain is expected within 2 hours.
For the seam and fastener sealing in step four, the product choice matters as much as the field coat, which is why Uniflex specifies its own OneFlash sealant there. Our guide to metal roofing sealant covers which sealants hold at those exact junctions. Coating over active leaks does not work, so trace and fix them first using our metal roof leak repair walkthrough before you coat.
When is coating the right call, and when should you replace instead?
| If your roof has | Do this | Threshold or source |
|---|---|---|
| Sound panels, surface rust only, minor leaks at fasteners | Coat: wire-brush, prime rust, seal details, field coat | Henry 887 and Uniflex prep steps |
| Panels rusted through or structurally weakened | Replace those panels first, or reroof | Uniflex requires replacement of corroded panels compromising structural integrity |
| Laps gapping more than 1/8 inch | Refasten laps per the panel maker before coating | Uniflex spec |
| Low slope with ponding water | Silicone, not acrylic | Henry rates 887 for permanent ponding resistance; Uniflex verifies a 1/4 inch per foot minimum slope |
| Bare galvanized, no rust | Silicone with no primer is allowed by Rust-Oleum 995 | Rust-Oleum 995 TDS |
| Bare steel or rusty metal | Rust-inhibitive primer first | Rust-Oleum 115 or Uniflex 34-520 |
| Cool shoulder season, nights near 40°F | Silicone (Henry 887 applies 35°F to 120°F) | Henry 587 acrylic needs 50°F and rising and no sub-50°F temperatures for 48 to 72 hours |
| Want a 15-year manufacturer warranty | Specify 2 gal per 100 sq ft of silicone in the contract | Uniflex 15-year UNIGUARD rate |
Reflective coatings trim summer heat gain: Henry 887 keeps 0.73 aged solar reflectance in its CRRC rating, against 0.88 when new. Our cool roof energy savings report quantifies how much reflective surfaces save by climate zone. A coated roof still needs upkeep, so pair any coating with a metal roof maintenance schedule of annual washes and inspection of the sealed details.
Frequently asked questions about metal roof coatings
Are metal roof coatings worth it?
Metal roof coatings are worth it when the panels are structurally sound but weathering, leaking at the surface, or driving high cooling bills. HomeGuide puts installed metal roof coating at about $0.50 to $4.00 per square foot, so compare that with a reroof quote and the coating maker’s warranty term before deciding. They are not worth it on rusted-through or structurally failing panels, which coating specs such as Uniflex’s require to be replaced first.
What is the best coating for a metal roof?
For low-slope or ponding-prone metal, high-solids silicone is the strongest fit: Henry 887 is 91% solids by volume with 280% elongation and is rated for permanent ponding resistance. Acrylic, such as Henry 587 at $0.50 to $3.00 per sq ft installed per HomeGuide, suits sloped metal in dry, sunny climates. Check the data sheet for your panel finish, since adhesion is decided by the substrate.
How long do metal roof coatings last?
Coating life tracks the warranty you buy with film thickness. Uniflex issues a 10-year warranty at 1.5 gallons per 100 sq ft of silicone (22 mils dry) and a 15-year warranty at 2 gallons (30 mils dry). Thin films, poor prep and unsealed seams and fasteners shorten that life, so get the specified rate in writing.
Can you coat a rusted metal roof?
You can coat a metal roof with surface rust, but only after wire-brushing loose rust and applying a rust-inhibitive primer, such as Rust-Oleum 115 or Uniflex 34-520, so the coating bonds to sound metal. Coatings encapsulate light surface oxidation. They cannot rescue panels that have rusted through or lost structural integrity, which need replacement.
Do you need to prime a metal roof before coating?
Usually. Per its 995 data sheet, Rust-Oleum allows bare galvanized metal with no rust to take the silicone unprimed, but bare steel and rusty metal must be primed. Henry’s 587 acrylic sheet calls for its 107 sealer first on previously uncoated metal. Factory Kynar finishes are slick and usually need scuffing, a compatible primer and an adhesion test.
Can you put silicone coating over acrylic, or acrylic over silicone?
Acrylic and paint do not bond to cured silicone, so a silicone roof is recoated with silicone. Silicone over an aged acrylic coating can work: Rust-Oleum lists aged acrylic coatings as a 995 substrate, subject to an adhesion test. Henry’s 887 warranty is void if the roof is later coated with a non-approved product, so the first choice is a long-term system decision.