Flat Roof Coatings

Right for: aging modified bitumen with surface UV degradation but intact plies. Aging EPDM with degraded seams or surface oxidation but no membrane punctures. Aging metal roofs with intact panels but failing exposed-fastener gaskets. Built-up asphalt roofs (BUR) where the gravel ballast is intact and the underlying plies haven't fully failed. Most flat-roof situations where the owner is debating coating vs replacement.

Not right for: roofs with structural membrane damage (punctures, tears, large blisters), saturated insulation underneath the membrane (water trapped between deck and membrane — coating traps the moisture and accelerates rot), low-slope conditions with ponding water exceeding 48 hours after rain (ponding chemically attacks most coatings), or roofs already at the end of their actual structural service life where coating would mask underlying failure.

Diagnostic step matters. We do an infrared moisture scan on every coating candidate over 5,000 sq ft — IR scan shows wet insulation underneath the membrane (heat signature differs). Wet insulation must be removed and replaced before coating, or the entire coating effort fails within 5 years.

Manufacturer eligibility. GAF, Carlisle, Mule-Hide, and other major coating manufacturers offer enhanced warranties (10-20 years) only on properly prepped, code-compliant substrates with verified moisture content. We document the prep and submit for warranty registration on every coating system we install.

Silicone (GE Enduris, GAF Unisil, Mule-Hide 100% Silicone). The premium choice for most NJ commercial flat-roof coating work. 100% silicone formulations handle ponding water indefinitely, hold up under UV for 20+ years, and don't require yearly recoats. Higher upfront cost than acrylic but dramatically longer service life. White reflective surface meets Energy Star + cool-roof requirements.

Acrylic / elastomeric (Mule-Hide Acrylic, Henry Tropi-Cool 70). Water-based, lower cost than silicone, easier to apply, but degrades under standing water and requires periodic recoats (5-10 year cycle). Right for budget-driven projects on well-drained roofs. Not recommended for roofs with any ponding.

Polyurethane (Mule-Hide Polyurethane, Karnak). Highest abrasion resistance — used on roofs with heavy foot traffic (HVAC service decks, roof gardens, restaurant equipment access). Premium price. Not common on most commercial flat roofs.

SPF (spray polyurethane foam) systems. A different category — adds insulation value plus waterproofing in one application. Right for buildings where insulation upgrade is part of the goal. Requires SPF-certified installer and specific weather windows for spray.

Modified bitumen restoration coatings (GAF Liberty cap sheet over silicone primer, etc.) — hybrid systems specifically for restoring failed modified bitumen. Less common than pure silicone but right for specific substrates where pure coating doesn't bond well.

Power wash. Every coating substrate must be physically cleaned before coating. Dirt, debris, mold, and oxidized membrane surface must come off — coatings bond to clean material. We power wash at proper pressure (high enough to clean, low enough not to damage the substrate) and let the roof dry fully.

Seam reinforcement. Any seam failure, blister, or puncture gets cut out and patched with manufacturer-recommended seam tape and primer before coating. Coating alone doesn't bridge active failures — it amplifies them by trapping water underneath.

Primer. Silicone coatings require silicone-compatible primer on most substrates (specifically modified bitumen). Skipping primer is the most common failure point we see when reviewing other contractors' coating jobs that failed at year-3.

Two-coat minimum for warranty. Manufacturer warranties on silicone, acrylic, and polyurethane systems require two-coat application at specified mil thickness. Some installers single-coat to save material; that voids the warranty and produces a thinner film that fails early.

Detail work at curbs, drains, and penetrations. Every HVAC curb, scupper, drain, and pipe penetration gets reinforcement fabric embedded in the coating before the field coat. This is where coatings either succeed or fail — the flat field is easy; the details are everything.