# Roof Coating Application

> Roof coating application cleans, repairs and primes an existing roof, then sprays or rolls on a liquid membrane such as acrylic, silicone or polyurethane.

- URL: https://roof.wiki/roof-coating-application/
- Topic: Installation & Methods
- Also known as: roof coating installation; liquid-applied roofing; fluid-applied membrane; cool roof coating application
- Regions: Global
- First published: 2026-11-02 · Last reviewed: 2026-11-02
- Cite as: "Roof Coating Application." roof.wiki. https://roof.wiki/roof-coating-application/

## Key facts

- **Common types:** Acrylic, silicone, polyurethane, polyurea
- **Dry film thickness range:** About 0.075 mm (3 mils) to over 1 mm (40 mils)
- **Methods:** Airless spray, roller, brush

A **roof coating** is a fluid-applied layer that cures into a continuous, elastic film over an existing roof or new substrate. Coatings are used to protect spray foam, extend the life of ageing low-slope roofs, reflect sunlight (cool roofs) and seal metal roofs. Common chemistries include **acrylic**, **silicone**, **polyurethane**, **polyurea**, **butyl**, **styrene-butadiene** and bitumen-based coatings.

## Suitability

Not every roof is a candidate. The existing system must be mostly dry and structurally sound, since coating over wet insulation traps moisture. Some coatings are not rated for ponding water; acrylics generally are not, while some silicone and polyurethane coatings are warranted for it by their manufacturers. Coating asphalt shingles and certain built-up roofs is generally discouraged, because the coating can trap moisture or may not be compatible.

## Typical sequence

1. **Survey.** Check for wet areas (often with infrared or moisture meters), blisters, open seams and failed flashings.
2. **Clean.** Pressure-wash to remove dirt, chalking and biological growth, and allow to dry.
3. **Repair.** Replace wet insulation, reseal seams, reset fasteners on metal roofs and treat rust.
4. **Prime** where required for adhesion or to block bleed-through from bitumen.
5. **Reinforce details.** Apply fabric-reinforced coating or seam sealers at seams, flashings, drains and penetrations.
6. **Apply the field coats** by airless spray, roller or brush, in one or more coats to the specified thickness.
7. **Check thickness.** Wet film thickness is measured during application, and dry film thickness after curing.

## Thickness

Coatings range from about 0.075 mm (3 mils) to more than 1 mm (40 mils) dry film thickness, depending on the product and the warranty term sought. Thickness, not the number of gallons applied, determines performance.

## Weather limits

Each product has limits for air and surface temperature, humidity, dew point and time before rain. Water-based acrylics are sensitive to cold and rain during cure; solvent-based and moisture-cure products have their own restrictions. Manufacturers' data sheets set these limits.

## Maintenance

Coatings are renewable: many systems are designed to be cleaned and recoated at intervals to restore thickness and reflectivity.

## Sources

1. Roof coating — Wikipedia. https://en.wikipedia.org/wiki/Roof_coating
2. Canadian Roofing Reference Manual: 13.1.2 Potential Problem Areas — Canadian Roofing Contractors Association. https://roofingcanada.com/docs/canadian-roofing-reference-manual/canadian-roofing-reference-manual-chapter-13-troubleshooting-and-repairs/13-1-identify-cause-of-problem/13-1-2-potential-problem-areas/