Moisture Under the Membrane
The condition that rules a coating out most often cannot be seen from above. Wet insulation under an intact membrane holds heat and water, and a new coating over it traps the moisture and blisters within a season or two. Before we propose restoration on a roof of any size, we recommend an infrared moisture survey with core cuts to confirm what the camera suggests, and we mark every wet area on the roof so the owner can see its extent.
If the wet areas are small, we cut them out, replace the insulation and patch the membrane, and the coating proceeds. If they spread across the roof, the sound advice is to replace the system and not paint over a problem. Owners tend to respect that answer more than a hopeful one, especially on warehouse roofs and flex buildings like those along East Foothill Boulevard in Lamanda Park, where a single wet corner can trace back to a drain that has been backing up.
Silicone, Acrylic and Standing Water
The two coatings we apply most behave differently where water stays. A silicone roof coating tolerates ponding well, which makes it a sensible choice on a low roof that holds a shallow pool after a rain, though it attracts dirt and needs a roof that has been cleaned thoroughly before application. An acrylic roof coating is a good, reflective answer on a roof that drains cleanly, but it does not like to sit under water for days, and a roof that ponds should be corrected first.
Metal roofs are a different substrate again. Rusted panels are brushed back, fastener heads are sealed and over-coated, and panel laps are reinforced with fabric and mastic before the field coat. Hand-formed details at ridges, penetrations and the base of every curb matter more than the field itself, because that is where a coating cracks first when the sheet metal beneath it moves with the heat.
Reflectance, Heat and the Energy Code
California's cool roof rules apply to low-slope commercial roofs, and a coating is often the least intrusive way to meet them, though a full cool roof installation is the better route when the old membrane is spent. Under the 2025 energy code, a low-slope commercial roof that is new or substantially altered must test at 0.63 for reflectance after aging, paired with 0.75 for emittance, or else reach an SRI of 75, and the city's permit center enforces that from January 2026. We confirm with the city how a given restoration is treated before the scope is final, and we choose a coating whose aged values clear the line, not just its new ones.
Heat is the other reason owners come to us. A dark membrane, whether over a laboratory, a convention hall like the Pasadena Convention Center's exhibition building or a flex unit on East Foothill Boulevard, can run far hotter than the air above it, and a bright coating lowers that surface temperature, relieving the thermal cycling that cracks flashing and seams. The city's mapped fire hazard zones sit generally in the Arroyo Seco and in upper Hastings Ranch, and where a property sits in the Very High zone the roof covering must also be Class A once more than half of it is replaced in a year, so we check the assembly rating of the finished roof before proposing a coating over it.
When a Coating Is the Wrong Tool
A coating extends the life of a good roof and does nothing for a failed one. If the membrane has split across its field, the insulation is saturated across a wide area, or the deck has softened, the right answer is full roof replacement, and we put that in writing with the reasons. A restoration over a roof in that condition would only be a paint job with a short life.
On the roofs where it works, the coating needs a second layer of attention. We schedule a recoat when the dry film has thinned, clean the surface periodically, and fold the roof into our preventive maintenance visits so that seams and details are rechecked every year. The building's owners get a coating that was applied to a prepared roof and kept clean after, with the inspection history to prove it.
Commercial Roofing Questions
How do you know whether my roof is a candidate for a coating?
We start with a walk, a moisture survey and a few core samples, and the findings sort the roof into restore or replace. A membrane that is basically sound with dry insulation is a candidate. One with wide wet areas or deep splits is not, and we say so before any coating is priced.
Silicone or acrylic for a low-slope roof that ponds after rain?
Silicone is usually the better fit where shallow water stays for a day or two, since it holds up under standing water in a way that acrylic does not. Even so, ponding is a drainage problem, and we look at whether a cricket or a drain adjustment would cure it. A coating that survives ponding is a compromise, not a fix.
Will the coating satisfy the cool roof requirement?
The requirement turns on aged reflectance and emittance, so a coating has to be chosen by its three-year aged values and not its brochure numbers. We check those values against the energy code and confirm with the permit center how a restoration is classified. If the coating clears the line, we document that in the file.
What does the tenant notice while the roof is being coated?
Some odor from the material, a few days of foot traffic overhead and the occasional restriction on rooftop access. We schedule the work around intake vents and quiet hours, and warn the property manager about the days when equipment will be shut off or masked. The interior stays undisturbed.
How long before the roof needs recoating?
Recoating timing follows product, film thickness, dirt, and foot traffic. We measure the installed film and recheck it during maintenance.
