A roof coating is a monolithic, fully adhered, fluid applied roofing membrane. It has elastic properties that allows it to stretch and return to their original shape without damage.
Typical roof coating dry film thickness vary from paint film thickness (plus or minus 3 dry mils) to more than 40 dry mils. This means a roof coating actually becomes the top layer of a composite roof membrane and underlying system. As such, the roof coating is the topmost layer of protection for the membrane, receiving the impact of sunlight (both infrared and ultraviolet (UV), rain, hail and physical damage.
Roof Coatings should not be confused with Deck Coatings. Deck Coatings are traffic bearing – designed for waterproofing areas where pedestrian (and in some cases vehicular) traffic is expected. Roof Coatings will only waterproof the substrates but will not withstand any kind of on going use by people or vehicles (such as walkways, patios, sundecks, restaurants, etc.).
Metal Roof Coatings
Several different types of coatings are used on metal panels: anti-rust, waterproofing, heat reflective. They are made of various materials such as epoxy and ceramic.
Untreated Metal roofs absorb and retain heat which causes high building envelope heat loads.
Can be applied on metal roof materials to add heat reflective characteristic. Most ceramic coatings are made from regular paint, with ceramic beads mixed in as an additive. Although an average ceramic coated roof material reflects 75% to 85% of solar radiations, performance drops by over 30% after a few years due to dirt build-up. Their composition and thickness (from 500 to 1,000 micrometres) can cause cracks to appear, and the color selection is generally limited to white matte finish.
Coatings are sometimes applied to copper. Clear coatings preserve the natural color, warmth and metallic tone of copper alloys. Oils exclude moisture from copper roofs and flashings and simultaneously enhance their appearance by bringing out a rich luster and depth of color. The most popular oils are Lemon Oil, U.S.P., Lemon Grass Oil, Native E.I., paraffin oils, linseed oil, and castor oil. On copper roofing or flashing, reapplication as infrequently as once every three years can effectively retard patina formation.
- A metal roof graded “AG” or “Utility” will need recoating once the factory finish wears off, or corrosion will occur. These paints are commonly acrylic or polyester based. Roof coatings are the preferred material since they are able to stay elastic and withstand the thermal cycling that occurs in metal roofs.
- Roofing materials made from stainless steel, zinc or copper will rarely require maintenance over their lifetime. Any required maintenance is usually due to design or installation mistakes. Otherwise, these materials commonly last over a century.
- Metal roofing with long life polymer coatings like Kynar should not normally require maintenance until the coating fails. These products have been used for over half a century now in the U.S. and few installations have failed. They should be considered lifetime products.