Roof Waterproofing Coatings · an Amrize brandFibre-reinforced silicone repair compound — trowel-applied to cracks, voids, fixings and lap seams before coating. Bonds even to damp surfaces.
The jobs this product is specified for, day in day out.
Filled and bridged before coating, so the membrane is not asked to span a gap.
Trowel-grade material worked around awkward details a brush cannot fill.
Bonds to damp surfaces, so a leak can be stopped before the coating programme starts.
What the data sheet actually gives you on site.
Most repair compounds need a dry substrate. This one does not — which is why it doubles as the emergency repair on a wet roof.
Reinforcement built into the compound, no fabric to bed in.
Moisture-curing silicone that is ready to overcoat in hours, not days.
Compatible with every GacoFlex silicone coating — one chemistry across the whole build-up.
The facts that matter, straight from the product data.
| Type | Single-component, moisture-curing silicone repair compound |
| Use | Cracks over 6 mm, voids, punctures, bolts and fixings, lap seams, emergency repairs |
| Coverage | Approx. 18 linear metres at 50 mm width per 3.78 L tub |
| Cure before overcoating | 4–8 hours |
| Compatibility | All GacoFlex silicone coatings |
Everything from the manufacturer’s literature — open the part you need.
GacoPatch is ideal for roof waterproofing permanent patch repairs:
Sealing surface cracks, control joints, coping joints, fishmouths, rain collars, and roof seams
Gutter seams, pitch pans, small punctures or holes in flat and pitched roofing systems
Repairs on aged asphalt membranes (BUR, APP, SBS), modified bitumen, single-ply, metal, and GRP
Suitable for emergency repairs where instant waterproofing is required without waiting for dry conditions
Use with sacrificial polyester tape for dynamic cracks or movement joints over 6 mm (¼”)
Mix thoroughly before use (avoid paint shakers—use power mixing)
Apply with brush, trowel, putty knife, or 20 oz sausage gun
Apply at a minimum 1/8″ (3.2 mm) thickness, extending patch area by 3″ on all sides
Can be applied to damp surfaces (ensure no standing water)
Do not thin or dilute—use as supplied
Recommended temperature for application: 4 °C to 49 °C (keep material above 18 °C if cold)
Remove loose dirt, moss, dust, and debris using a stiff brush or power wash
Do not power wash asphalt substrates—clean with dry methods only
Rust and scale should be wire-brushed; gloss surfaces should be abraded before cleaning
Surface may be damp but not wet—standing water must be removed
Ensure surface is clean, sound, and free of oil or grease
Primer is not required for most substrates including asphalt, metal, and aged single-ply
Primer recommended for new TPO, PVC, or chalky surfaces—perform adhesion test if unsure
No topcoat required—GacoPatch is UV stable and forms a durable finish
Optional overcoating with GacoFlex silicone roof coatings if desired for full-roof restoration
VOC Compliant: < 250 g/L standard / < 50 g/L Low-VOC version (EPA Method 24)
Meets ASTM performance standards (D412, D624, D2240) for tensile strength, elongation, and hardness
Flash point: 39 °C (103 °F)
Safe for use on commercial and residential buildings—non-food contact areas only
Solvent-based, low-odour product—ensure adequate ventilation
Not suitable for contact with drinking water or food surfaces
Wear gloves, safety goggles, and protective clothing during use
Clean tools immediately after use with 100% mineral spirits or GacoFlex T5110 solvent
Refer to SDS for full handling, PPE, and emergency guidance
Store between -18 °C and 24 °C in unopened containers
Shelf life: 2 years unopened from date of manufacture
Product may skin over if exposed to air—keep container sealed until use
Do not apply in freezing or excessively hot weather (outside 4 °C–49 °C range)
Do not apply over highly flexible joints subject to constant movement or mechanical stress
These products are designed to work together — buying the full system is what qualifies the warranty.
Written by our technical team — free to download, no email required.
PDFFlat Roof Application GuideFelt, asphalt, torch-on, single-ply & EPDM — free 7-page guide PDFPitched Roof Application GuideMetal, cement fibre & asbestos roofs — free 7-page guide PDFGacoPatch Data SheetOfficial Gaco technical data PDFGacoPatch BrochureUses and application overviewTell us about the building and we’ll spec the job free — the right system, the right quantities, and trade rates if you’re buying for a contract.
Tell us about your building and we’ll recommend the right system — foam, waterproofing or both — surveyed, specified and quoted at no cost.
