A roof coating suits a manufactured home roof that is still in good condition, or one with a few minor problems that are repaired first. It is not a fix for a roof that is rusted through, sagging or leaking in many places; that roof usually needs a roof-over or replacement. The U.S. Department of Energy makes the same distinction in its roof guidance (DOE, Guidelines for Selecting Cool Roofs).
What a roof coating is
DOE describes coatings as "like very thick paints" that protect the roof surface from ultraviolet light and chemical damage, with some adding water protection. It says more than 500 cool roof coatings are on the market, with products for most roof types (DOE guide).
Some products are sold specifically for manufactured homes. Rust-Oleum's LeakSeal RV and mobile home coating, for example, is described as a high-solids elastomeric coating for RVs, mobile homes, campers and trailers (Rust-Oleum product page). A coating is only as good as the surface under it and the way it is applied, so the product's data sheet matters more than the label on the front.
When a coating fits
DOE says a coating can extend a roof's service life as long as the roof is still in good condition. If the roof is in moderate condition and needs only minor repairs, it says a coating can go on after those repairs are made (DOE guide).
- The metal or membrane is intact, with surface rust at most.
- Leaks are few and their sources are clear.
- The roof feels solid, with no sagging or soft spots.
- The seams and penetrations can be sealed before coating.
When replacement or a roof-over fits better
DOE's guidance is direct: if a roof is in poor condition or near the end of its life, it is usually best to re-cover, replace or retrofit it. It adds that building a second roof over the old one depends on building codes and the roof's structural integrity (DOE guide).
- Rust has eaten holes through the metal.
- Leaks keep appearing in new places.
- The roof sags, flexes or feels soft, which can mean wet framing.
- Ceiling damage is spread across the home.
A coating won't strengthen framing. Under the HUD standard, the roof structure must carry its design loads without exceeding allowed deflection (24 CFR 3280.305(h)(1)). If the framing is in question, deal with it first.
Coating or replacement: a side-by-side look
| Question | Coating | Roof-over or replacement |
|---|---|---|
| Roof condition | Good, or moderate with minor repairs done first (DOE) | Poor or near the end of its life (DOE) |
| Framing | Must already be sound; coating adds no strength | Can be inspected and repaired as part of the job |
| Prep work | Cleaning, sealing seams, flashing penetrations, priming rusty steel (Rust-Oleum 710 data sheet) | Depends on the system; a roof-over adds purlins and new flashing |
| Licensing | Repairs to structure need the right license | Structural work may need a Manufactured Housing Board license |
How coating prep works
Manufacturer data sheets spell out the prep, and skipping it is a common reason a coating fails. The data sheet for Rust-Oleum 710 Elastomeric Roof Coating, which lists metal roofs among its surfaces, sets these conditions (Rust-Oleum 710 technical data):
- The surface must be clean and free of dirt, grease, mold, algae, loose paint, rust and other material that could stop adhesion.
- Seams should be sealed and roof penetrations flashed before the topcoat goes on.
- Steel, and rusty or corroded metal, must be primed.
- Reinforcement fabric must be used for repairs and alligatored surfaces.
- Apply only when air, material and surface temperatures are between 50 and 100 degrees F and relative humidity is below 85 percent.
The same sheet warns that scraping or sanding old paint can release lead dust. That is worth knowing on an older home. Other products have their own rules, so read the data sheet for the one you buy.
Energy claims: read them carefully
Reflective coatings are often sold on energy savings. DOE says cool roofs "do not perform equally well everywhere" and that the decision should be weighed carefully (DOE guide). Treat any savings figure on a label as the maker's claim for its test conditions, not a promise for your home.
Questions to ask before you coat
- Is the roof surface listed on the product's data sheet: bare metal, painted metal, or the material you actually have?
- Which primer, if any, does the data sheet require for that surface?
- Have all leaks been traced and repaired, and have seams and penetrations been sealed?
- Is the weather forecast inside the product's temperature and humidity limits for the full cure?
- Does the roof feel solid everywhere, with no sagging or soft spots?
- What does the product warranty require, and does a missed prep step void it?
If several answers are "no" or "not sure", a coating is likely to fail early. Our leak repair post covers how to trace leaks before you coat.
Who should do the work
You can coat your own roof. HUD's guidance says owners should be able to make repairs, though a home under the manufacturer's warranty may need the manufacturer's approval first (HUD homeowner resources). If you hire someone and the job touches the structure, South Carolina requires a Manufactured Housing Board license or another state license covering that trade (S.C. Code § 40-29-30(A); Reg. 79-24(D)). Our manufactured home roofing guide explains the licensing rules and permits.
