Silicone roof coatings · an Amrize brandThe 100% silicone, solvent-free roof coating system used on commercial roofs — a single-coat membrane that survives ponding water, stays UV-stable, and carries up to a 20-year manufacturer warranty. Three products, one chemistry: S4200 White, S4222 Gray and SF4200 SeamSeal.
S4200 · SF4200 · S4222One chemistry across the roofs that cost building owners the most — coated in place, with the building staying open.
Felt, asphalt, torch-on, single-ply and EPDM. Silicone does not re-emulsify in standing water, so ponding areas that destroy acrylic coatings are exactly where this system belongs.
Direct adhesion to weathered sheet with no primer on most substrates. In White it reflects most of the solar load, so the sheets run cooler and work their fixings and laps less.
Seals and extends the life of failing cement sheets from above — no cutting, no drilling, no disturbance, and no tear-off or skip.
What the data sheet actually gives you on site.
Silicone chemistry does not re-emulsify in standing water — the failure mode that ends acrylic coatings on flat roofs.
Highly UV-stable, so the membrane keeps its film and its reflectance instead of powdering off over a few summers.
Strong direct adhesion to metal, spray foam, aged bitumen and aged single-ply. Concrete and some membranes need a primer — we tell you when.
Both warranty tiers go on in a single coat at 96.5% solids, by whichever method suits the roof and the access.
Clean, detail, repair, then coat. Same silicone chemistry through the whole system, so the roof cures as one membrane rather than a stack of dissimilar materials.
The reflective field coat for the whole roof, in White or Gray — same chemistry, same warranty tiers, same single-coat application. White gives the highest solar reflectance; grey is chosen where a white roof is not wanted, or as the second-pass colour so coverage can be checked by eye.
Fibre-reinforced silicone for laps, seams, upstands, penetrations and fixings — the places roofs actually leak. Reinforcement is built in, so there is no fleece or scrim to buy and bed in.
Trowel-grade silicone for cracks over 6 mm, voids, punctures and bolt heads. Bonds to damp surfaces, so the repair stage does not have to wait for a dry week.
The base coat that stops aged bitumen and asphalt bleeding through the silicone and staining it. Only needed on those substrates — metal, asbestos cement and aged single-ply take S42 direct.
Film thickness alone decides the tier. It is a single-coat system in both cases — applying white then grey is a coverage-checking method, not a second coat.
Worked out the way our estimators do it: plan area × pitch factor × corrugation allowance = the developed area your coating actually has to cover. Pail counts use our real per-pail yields for each warranty build.
The facts that matter, straight from the product data.
| Type | 100% silicone, solvent-free, moisture-curing liquid roof coating |
| Solids | 96.5% — wet film is effectively the dry film |
| System | Single coat; film build sets the warranty tier |
| Warranty builds | 0.45 mm / 18 mil dry (10-year) · 0.86 mm / 34 mil dry (20-year) |
| Coverage | Approx. 33 m² (10-year) or 21 m² (20-year) per 19 L pail |
| Colours | S4200 White · S4222 Gray |
| Substrates | Metal, asbestos cement, aged bitumen and felt, single-ply, EPDM, spray foam; concrete and some membranes need a primer |
| Application | Airless spray, brush or roller |
| Detailing | SF4200 SeamSeal at all laps, seams, upstands, penetrations and fixings |
| Manufacturer | Gaco — an Amrize brand. Duratite is the supplier in Ireland |
Five steps. Miss one and the warranty position changes.
Biocidal clean with Sollac Hipolava at 20:1, 10–15 minute dwell, then rinse. The coating must bond to the roof, not to moss.
SF4200 SeamSeal at every lap, seam, upstand, penetration and fixing. Fibre-reinforced, so no scrim.
GacoPatch into cracks over 6 mm and voids — it bonds even to damp surfaces.
Only where needed: A4271 Bleed Trap on asphalt and bleed-prone felt, primer on concrete and some single-ply.
S4200 or S4222 in a single coat to the film build your warranty tier requires.
Written by our technical team — free, no email required.
PDFS42 Flat Roof Application GuideFelt, asphalt, torch-on, single-ply & EPDM — 7-page guide PDFS42 Pitched Roof Application GuideMetal, cement fibre & asbestos roofs — 7-page guide TDSGacoFlex S42 Data SheetOfficial Gaco technical data TDSGacoFlex SF42 SeamSeal Data SheetDetailing grade technical dataFree take-off from your dimensions, the right warranty tier for the building, and trade rates if you’re buying for a contract. Surveyed and specified before you order.
Tell us about your building and we’ll recommend the right system — foam, waterproofing or both — surveyed, specified and quoted at no cost.
