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shop@flatroofingsystems.co.ukGacoFlex S42 (S4200) Silicone Roof Coating - 18.9Ltr Drum
Manufacturer/Brand: Gaco
SKU:S4222-5
In stock
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Restore and waterproof ageing roofs with GacoFlex S42, a solvent-free, single-component silicone roof coating available in White or Grey. Designed for suitable flat, low-slope and pitched roofs, it provides a practical refurbishment option without removing a sound existing roof covering.
Applied by brush, roller or spray, GacoFlex S42 moisture-cures to form a seamless, fully adhered waterproof membrane. Its resistance to permanent ponding water and UV exposure makes it particularly suited to flat roofing applications.
GacoFlex S42 forms the main waterproofing membrane within the GacoFlex silicone roof system. Supplied ready to use, it requires no mixing with a separate hardener.
Key Features:
- 100% silicone coating – solvent-free and single-component.
- Resists permanent ponding water – suitable for roof areas where standing water occurs.
- UV-stable protection – withstands exposure to sunlight and weathering.
- Seamless waterproof finish – forms a continuous membrane without laps or joints in the coating.
- Flexible application – apply using suitable spray equipment, a brush or roller.
- Solar-reflective White finish – initial solar reflectance of 0.87.
- High adhesion – bonds to many common roofing surfaces, subject to preparation and any specified primer or base coat.
Suitable Applications
- GacoFlex S42 can be used to restore and protect a range of suitable, correctly prepared roof surfaces, including:
- Felt and asphalt flat roofs.
- Single-ply roof membranes.
- Profiled metal roofs.
- Fibre-cement and asbestos cement roofs, subject to appropriate assessment and specialist preparation.
- Spray polyurethane foam roofing.
For bituminous roofs, apply GacoFlex A4271 Bleed Trap base coat before S42 to help prevent bitumen staining through the finish.
Pail Size, Colours and Coverage
- Pail size - 18.9 litres.
- Colours - White or Grey.
- Approximate coverage at 10-year film build - 33m² per pail.
- Approximate coverage at 20-year film build - 21m² per pail.
- Application - Brush, roller or spray.
- Curing method - Moisture-curing.
Coverage figures are approximate and depend on the surface texture, condition and application losses. Allow additional material for upstands and roof details. The film-build references do not, on their own, confirm a guarantee; any warranty is subject to the applicable system specification and manufacturer’s terms.
Preparation and Application
The existing roof must be sound, clean and suitably prepared before application. Address defects and prepare joints, penetrations and upstands in accordance with the specified system. Some substrates require a compatible primer or base coat, and adhesion testing may be necessary.
Correct preparation and detailing are essential to a successful roof coating application. The following complementary products are available separately:
GacoFlex S42 Seam Sealant: For sealing roof seams, fasteners and intricate details.
GacoFlex A4271 Bleed Trap: A bleed-blocking base coat for use where required by the substrate specification.
GacoPatch: For filling large cracks, splits and joints before applying the roof coating.
Always follow the current GacoFlex technical data sheet for substrate suitability, application conditions, coating thickness and curing requirements. Asbestos-containing roofs require specialist assessment and safe working methods before any preparation or coating work.
Order GacoFlex S42 Silicone Roof Coating from All Flat Roofing Supplies, with UK-wide delivery.
Additional Information for GacoFlex S42 (S4200) Silicone Roof Coating - 18.9Ltr Drum
Delivery Information
Delivery Information
Gaco roof coatings are delivered directly to your chosen address through our network of courier and pallet delivery services. Delivery typically takes 1–3 working days, although remote locations and busy periods may require slightly longer. Delivery times are estimates and cannot be guaranteed.
Please advise us before dispatch of any access restrictions, road closures or other circumstances that could prevent or delay delivery. Delivery vehicles may range from small vans to rigid and large articulated HGVs. We cannot control which vehicle is allocated to your order.
We strongly recommend that you do not schedule roofing works until your order has been received in full and checked.
Checking Your Delivery
Please inspect your order on arrival. Any visible damage should be recorded on the delivery paperwork, and any damaged items must be reported to our office within 48 hours of delivery. Photographs of the packaging and affected products will help us resolve the matter promptly.
Tins may occasionally become dented or distorted during transport. Cosmetic dents do not normally affect the contents or their suitability for use, provided the tin remains sealed and intact, we would not normally refund or exchange. If a tin is split, leaking, open or has a damaged seal, please report it as a damaged item.
Returns Information
Returns are accepted within 14 days of delivery. Please contact our office before returning any products so we can confirm the correct procedure and return address. The return address may differ from our operational depot.
Products must be unused, unopened and in their original condition. For change-of-mind returns, you are responsible for the return delivery costs and for ensuring the goods are securely packaged.
Returned goods remain your responsibility until they have been received and inspected by our customer service team. We recommend using a tracked delivery service with suitable cover for the value of the goods. We cannot refund items that are missing from the return or arrive damaged.
These conditions do not affect your statutory rights, including those relating to faulty, damaged or incorrectly supplied goods.
FAQ's
What is GacoFlex S42 Silicone Roof Coating used for?
GacoFlex S42 (S4200) is designed to restore and waterproof suitable existing flat and low-slope roofs. It forms a seamless, flexible silicone membrane that helps extend the life of a weathered roof.
Which roof surfaces can GacoFlex S42 be applied to?
It is suitable for a range of compatible substrates, including felt and bituminous roofing, EPDM rubber, GRP/fibreglass, metal and fibre cement. Always carry out an adhesion test and follow the manufacturer’s preparation requirements before application.
Does GacoFlex S42 require a primer?
GacoFlex S42 bonds directly to many correctly prepared substrates without a primer. However, an adhesion test is essential, and some surfaces may require a primer or specialist base coat. GacoFlex A4271 Bleed Trap is available where a bleed-blocking base coat is specified.
Can GacoFlex S42 withstand standing water?
Yes. GacoFlex S42 is designed to withstand permanent ponding water without softening, bubbling or degrading. The roof must still be suitable for refurbishment and prepared in accordance with the manufacturer’s instructions.
How much roof area will an 18.9-litre drum cover?
The advised coverage is 33m² per drum for the 10-year guarantee specification or 21m² per drum for the 20-year guarantee specification. Surface texture, porosity and detailing can affect the quantity required. Always achieve the manufacturer’s specified coating thickness.
Does GacoFlex S42 come with a guarantee?
The manufacturer offers 10-year or 20-year product guarantee options, subject to its terms and conditions. The roof coating must be installed correctly at the required coverage rate and in accordance with the manufacturer’s specifications and guidelines.
Can GacoFlex S42 be applied in one coat?
A single-coat application is possible in many circumstances. This depends on the substrate, its condition and the required specification. Always follow the manufacturer’s guidance for your particular roof.
Should cracks, joints and roof details be repaired first?
Yes. Prepare and repair the roof before applying the main coating. GacoPatch is available for filling large cracks, splits and joints, while GacoFlex S42 Seam Sealant is designed for roof seams, fasteners and intricate details.
What colours and sizes are available?
GacoFlex S42 is supplied in 18.9-litre drums, with a choice of Grey or White.