How Often Should a Flat Roof Be Coated?

Periodically coating a flat roof may double the roof's lifespan. While most flat roofs last at least 10 years, coating it every five to eight years can double its useful life, as well as save you money. All flat roofs are not alike, and how often such roofs should be coated depends on the materials, climate and any needed repairs.

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Periodically recoating a flat roof extends its useful life.

Flat Roofs

If a roof only slopes slightly, it is generally referred to as a flat roof. The most common types of roofing materials for such roofs in the past included tar and gravel or built-up roofing. Modern flat roofs may consist of single ply or modified bitumen roofing. Regular maintenance plays a large role in the roof's lifespan. Because of drainage issues affecting flat roofs, any problems should be corrected as soon as possible.


Maintenance includes repair of problems common to flat roofs, such as ponding. Ponding refers to excess water accumulation from rain on the roof. On flat roofs, ponding may affect the roof's structural integrity. On roofs with polyvinyl chloride surfaces, crazing may develop. These are fine cracks on the PVC. Failure to repair crazing may result in serious roof deterioration. Alligatoring refers to a similar issue, but on roofs covered in bituminous materials.


The coating for a flat roof varies, depending on the roof's substrate and whether the coating adheres. Usually, coatings don't adhere as well to smooth and hard surfaces, in contrast to irregular or rougher surfaces. Coatings do not adhere as well to chemically inert surfaces as they do to chemically active surfaces. To improve the coating's adhesion, use a base coat or primer beforehand, as recommended by the coating manufacturer. Coatings are available for specific types of roof membranes and substrates.

Other Coating Considerations

Coating the roof periodically offers additional advantages besides extending its lifespan. It lowers the temperature of the roof, which may result in utility bill savings. Various coatings include different performance factors. Make sure that all necessary roof repairs are completed before coating is applied. It is also imperative that the correct coating for the particular substrate is applied, so consult with the roofer or manufacturer to ensure that the proper product is used on your roof. Ask to see the product's material safety data sheet.