A roof coating is a liquid membrane rolled or sprayed over the roof you already have. It cures into one seamless skin, so the old membrane's laps stop being leak paths. It bridges small splits, wraps penetrations, and reflects heat instead of holding it. Most of the calls we get about coatings come from property managers and owners who know a replacement is coming eventually and don't want it this year. The building is leaking in two spots, tenants are complaining, and a tear-off means dumpsters in the lot and a shut loading dock. That's a reasonable thing to want.
But a coating is restoration, not replacement. It goes over the roof you have. It doesn't undo the roof you have, it adds no R-value, and it doesn't satisfy the insulation code you'll face whenever the real replacement happens. It defers that. It also only works on a roof with something left worth saving. Coat over a wet roof and you seal the water in, and now you have a wet roof you can't see. We'll tell you plainly whether the roof in front of us can do this job.
Handles standing water and UV better than anything else we put down. The trade-offs are real. It's slick when wet, so service routes and equipment access get walkway pads. It holds dirt, which means it loses reflectance faster than acrylic does. It's the softest of the three under foot traffic. And once a roof is siliconed, recoating it later realistically means silicone again.
Water-based, keeps its reflectance better than silicone, and cheaper per square to install. It needs weather to cure: roughly 50 degrees and rising, with a clear dry window, no rain, no dew, no cold night coming. That rules out late-day work in the shoulder season. And it's the wrong answer on a roof that ponds. Acrylic re-emulsifies in standing water and comes apart.
The toughest of the three underfoot: dropped tools, and the HVAC tech walking the same path every month. It's a two-part system, not one product: an aromatic urethane base coat for adhesion and build, then an aliphatic urethane on top, because the base coat chalks within a season if you leave it exposed to sun.
Wet insulation under the membrane, seams failing across the whole field, a soft substrate, or a roof already carrying two systems. You can't coat a dead roof. You only trap the moisture, the deck keeps deteriorating where you can't see it, and the tear-off gets worse and more expensive later. We'd rather lose the coating job than sell you one that fails.
A coating is only worth buying if we know what is under it. So before anyone puts a number on paper, we map the roof for moisture rather than guessing at it: an infrared or capacitance survey across the field, then core cuts to confirm what the survey flags. A core is a small square cut out and patched back. It tells us how many roofing layers are stacked up there, whether the insulation is dry, and whether the deck is sound. Layer count matters for a reason most owners are never told: code generally allows two roofing layers before a full tear-off is required. That single fact often decides coating versus replacement, and you should hear it before you budget, not after. We also check where water sits. Ponding at the low points means the drainage gets corrected first, whatever chemistry goes down after. And we put an adhesion test patch on the actual surface. Aged single-ply and any unknown prior coating can refuse to bond, and that gets confirmed, not assumed. If someone tells you how many years a coating will buy you before any of that has happened, they are guessing.
Prep decides whether the coating is still doing its job years out. The roof gets washed, usually detergent-cleaned too, because nothing bonds to chalk, dirt, or the grease film around a kitchen exhaust, and that wash water gets contained and disposed of properly, which matters more than people expect on a roof carrying kitchen grease. Rusted metal and bare substrate get primed. Every seam, lap, penetration, curb, and drain gets reinforced with fabric embedded in coating before any field coat goes on, and shot pitch pans get rebuilt. Then the field goes on at the thickness the product calls for, measured wet, not eyeballed. We work under South Coast AQMD, which limits VOC content in roof coatings more tightly than most of the country, so some products sold nationally are not legal here. We specify what is. On an occupied building we shut down or mask rooftop air intakes in the zone we are working, and pick low-odor or water-based product where the tenants make that necessary. Coatings almost never fail in the middle of the field. They fail at a detail somebody rushed.
The material usually isn't what rules it out. We coat over modified bitumen, single-ply, metal, and spray foam. Condition rules it out. Water in the system, a deck that's already failing, or a membrane that's shot rather than just tired, and coating is money spent on a delay you won't get. There's also a layer limit: if the roof is already carrying two systems, code generally sends you to a tear-off. And adhesion gets confirmed with a test patch on your actual surface, not assumed from the substrate type. Aged PVC and EPDM are the usual surprises.
Almost never. There's no tear-off, so the deck stays covered except where we're replacing a wet insulation area, and the noisy part is mostly the power wash. We schedule that around your hours. The bigger issue on an occupied building is odor, not noise. Solvent-borne product gets pulled straight into the space through rooftop air intakes, so we shut down or mask the intakes in the zone we're working, and where the tenant use demands it (medical, food, daycare), we specify low-odor or water-based product instead. We can also stage the work in sections so one area is affected at a time.
On most commercial low-slope jobs, yes. And that's worth knowing before someone else surprises you with it. Title 24 section 141.0(b)2B treats recoating as an alteration, and compliance kicks in at more than 2,000 square feet or more than 50 percent of the roof area, whichever is less. Almost any commercial recoat clears that. For nonresidential low-slope, the requirement applies in every climate zone. What it means practically is that the coating has to be a CRRC-rated product meeting the prescriptive aged solar reflectance and thermal emittance values, or the job goes down the U-factor exception path. We specify CRRC-rated product and hand over the documentation for the permit.
We'll come out, get on the roof, and put it in writing. Free inspection across LA and the Inland Empire.
