Flat Roof Coating & Waterproofing

How a Coating Repair Is Actually Done

The area gets prepped first — loose mastic, granules, and debris scraped away, since a coating applied over loose material won’t bond. An asphalt-based primer often goes down first to lock in remaining dirt and give the coating a clean surface to grip.

Coating is applied at a specific thickness: too thick and it cracks as it cures, too thin and it won’t hold. For anything beyond a pinhole, a fabric reinforcement layer gets embedded in the coating — it works the way rebar works in concrete, turning a repair that lasts a year into one that lasts five to ten.

Black Mastic vs. Silicone vs. Liquid Rubber

Different products suit different conditions. Black mastic-based systems are often preferred ahead of wet weather; silicone systems handle ponding water and UV exposure well long-term; liquid rubber coatings offer flexibility across temperature swings. We’ll recommend the right system for your specific roof and situation rather than defaulting to one product.

Acrylic coatings also come up in comparisons and are lower-cost upfront, but they generally are not rated for standing water and can degrade faster in areas where ponding is a known issue. For most Berkeley flat roofs we see, that trade-off makes silicone or mastic the more reliable pick over acrylic, even at a higher initial cost.

Frequently Asked Questions