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Gaco Roof Waterproofing Coatings · an Amrize brand

GacoRoof Silicone Roof Coating - 3.8 Litres

100% silicone roof coating in a DIY-friendly 3.8-litre tin — sheds, garages, porches, dormers and small flat roofs, with the same ponding-proof silicone chemistry as our commercial systems.

✓ 100% silicone✓ Two-coat system✓ Class A fire rated
£67.00 + VAT
📞 Not sure it's the right product? Call 01208 832 602 — we spec every job before you order, free.
GacoRoof Silicone Roof Coating - 3.8 Litres

Where GacoRoof goes

The jobs this product is specified for, day in day out.

DIY

Sheds & garages

Small roofs where a full commercial pail would be wasted.

Home

Porches & dormers

Awkward small areas a contractor would price heavily.

Repair

Small flat roofs

Extensions and outbuildings needing a proper waterproof membrane.

Why contractors choose GacoRoof

What the data sheet actually gives you on site.

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Withstands ponding water

The same silicone chemistry as our commercial systems — standing water does not re-emulsify it.

🎨

Nine colours

Alternate colours between coats so you can see your coverage, then finish in the colour you want.

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Class A fire rating

ASTM E108 / UL-790, and the White meets Energy Star and CRRC reflectance requirements.

🖌️

Roller applied

No spray kit needed — a 19–25 mm nap roller and two coats is the whole method.

Specification

The facts that matter, straight from the product data.

TypeSingle-component, air-dry elastomeric silicone roof coating
SystemMinimum 2 coats to a 0.56 mm / 22 mil total dry film (3–4 coats on textured surfaces)
CoverageApprox. 9–10 m² per 3.8 L tin per coat at 0.28 mm / 11 mil DFT
ApplicationSolvent-resistant 19–25 mm nap roller, or notched squeegee and back-roll on smooth decks — do not thin
RecoatFirst coat dry in 3–12 hours; recoat as soon as it can be walked on
PerformanceTensile 2 MPa, 150% elongation, 0.06 perm — withstands permanent ponding water (ASTM D412 / E96)
Fire / cool roofClass A (ASTM E108 / UL-790); White meets Energy Star and CRRC reflectance requirements
ColoursWhite, Gray, Green, Light Tan, Rustic, Medium Blue, Black, Brown, Red

Materials calculator

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Complete 2-coat system
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One 3.8 L tin covers about 9–10 m² per coat, so a finished two-coat roof works out near 5 m² per tin. Whole packs only — we always round up. For warranty jobs add the 10% film-build variance factor and detail work; call 01208 832 602 for an exact take-off.

Product detail

Everything from the manufacturer’s literature — open the part you need.

  • 95% Solids by Volume – Minimal Shrinkage, High Coverage
  • Suitable for Asphalt, EPDM, GRP, Cement-Fibre, Single-Ply, Asbestos and Metal Roofs
  • Seamless, Fully-Adhered Waterproof Membrane
  • Outstanding UV and Ponding Water Resistance
  • Reflective White Finish – 88% Solar Reflectance (Cool Roof Compliant)
  • VOC Compliant: 37 g/L (EPA Method 24)
  • Liquid-Applied: Eliminates Seams, Joins, and Fastener Issues
  • 20-Year Manufacturer Material & Labour Warranty
  • Silicone Roof Coating

GacoFlex S4200 Silicone Roof Coating is ideal for waterproofing and restoring:

  • Aged Built-Up Asphalt Roofs (BUR)
  • Modified Bitumen (SBS/APP)
  • EPDM and TPO Single-Ply Membranes
  • PVC and Hypalon Roofs
  • GRP / Fibreglass Roofs
  • Asbestos Cement and Fibre Cement Roof Sheets
  • Corrugated or Standing Seam Metal Roofs
  • Commercial, Industrial, Institutional, and Public Sector Flat Roofs
Application Methods
  • Surface Preparation
    All roofing substrates must be clean, dry, and structurally sound. Remove debris, loose coatings, algae, and contaminants using GacoWash and high-pressure rinsing. For asbestos cement, encapsulate rather than disturb the substrate. Perform adhesion tests to determine if priming is necessary.
  • Primer Application (If Required)
    Apply GacoPrime LVOC or E5320 Primer to aid adhesion on substrates like EPDM, PVC, GRP, oxidised metal, or asbestos cement. Ensure complete cure before proceeding.
  • Detailing & Reinforcement
    Reinforce all seams, penetrations, fasteners, cracks, and joints with GacoPatch, SF4200 SeamSeal, or 66S Mesh embedded in S4200. These detailing components ensure watertight integrity over vulnerable areas.
  • Main Coating Application
    Apply GacoFlex S4200 Silicone Roof Coating at a minimum of 2.25 gal per 100 ft² to achieve a 34 mil dry film thickness. Apply in a single or dual-pass method using roller, squeegee, or airless spray. For added traction, broadcast white granules into a second coat while wet.
Application Equipment
Surface Preparation
  • Flat Roofs: Consider the condition of the existing roof deck, ensuring water is not trapped underneath the existing waterproof covering. Check the condition of the structural roof deck to ensure it is free from rot and decay or structural weakness. Ensure all seams and joins from the existing waterproofing covering is fully bonded. Ensure the existing covering is clean and dry using GacoWash. Seal all seams and penetrations, ensuring a minimum overlap of 50-75mm using Gaco SF42 Seam Sealant. Where asphalt or EPDM is aged, use Gaco Bleedtrap coating to prevent staining and leaching through of oils. A primer should not be required but carry out an adhesion test first. Apply Gaco S4200 at a minimum rate of 0.5 litres per square metre. Allow between 3-12 hours to dry (depending on environmental conditions) before applying any further coats.
  • Pitched/Sloped Roofs: Consider the condition of the existing roof deck, ensuring that it is not at the end of life. Clean the roof surface to be free from moss, dirt, grime and contaminants, using GacoWash as the cleaning agent. Pressure washing is recommended (consult HSE regulations for asbestos roofs). If using Gaco Roofing Foam, apply at minimum thickness of 15mm to seal all seams, joins and penetrations. If using Gaco SF42 Seam Sealant, use a brush or roller to seal all roof sheet seam, joins and penetrations, ensuring a minimum 50-75mm overlap on the seam. A primer is not required on most metal, cement-fibre or asbestos roof sheets but always conduct an adhesion test first. Apply Gaco S4200 at a minimum rate of 0.5 litres per square metre. Allow between 3-12 hours to dry (depending on environmental conditions) before applying any further coats.
Recommended Primers
  • Several compatible options available. Please consult Duratite for advice on suitable primers.
Topcoat Guidance

The same Gaco S4200 Silicone Roof Coating is used as the top coat. For ease of installation, consider using different colours for the base coat and top-coat. On flat roofs containing asphalt or EPDM, we recommend using a white coating to assist with solar reflectance, prolonging the protection of the roof deck whilst reducing solar gain.

  • VOC Compliant with EC & UK Regulations

Refer to the product-specific Product Health & Safety Data Sheet for complete guidance on handling, PPE requirements, and storage.

  • Application temperature must exceed 5°C and be 3°C above dew point.
  • Avoid moisture during drying to enable the coating to fully cure and dry.
  • High humidity and cold temperatures may prolong drying times.
  • Leave at least 4 hours before applying any further coats.
  • Depending on environment conditions, leave up to 24 hours for the coating to fully dry and cure.
  • 95% Solids by Volume – Minimal Shrinkage, High Coverage
  • Suitable for Asphalt, EPDM, GRP, Cement-Fibre, Single-Ply, Asbestos and Metal Roofs
  • Seamless, Fully-Adhered Waterproof Membrane
  • Outstanding UV and Ponding Water Resistance
  • Reflective White Finish – 88% Solar Reflectance (Cool Roof Compliant)
  • VOC Compliant: 37 g/L (EPA Method 24)
  • Liquid-Applied: Eliminates Seams, Joins, and Fastener Issues
  • 20-Year Manufacturer Material & Labour Warranty
  • Silicone Roof Coating

GacoFlex S4200 Silicone Roof Coating is ideal for waterproofing and restoring:

  • Aged Built-Up Asphalt Roofs (BUR)
  • Modified Bitumen (SBS/APP)
  • EPDM and TPO Single-Ply Membranes
  • PVC and Hypalon Roofs
  • GRP / Fibreglass Roofs
  • Asbestos Cement and Fibre Cement Roof Sheets
  • Corrugated or Standing Seam Metal Roofs
  • Commercial, Industrial, Institutional, and Public Sector Flat Roofs

GacoRoof is part of a system

These products are designed to work together — buying the full system is what qualifies the warranty.

Downloads

Written by our technical team — free to download, no email required.

PDFGacoRoof Product Data SheetOfficial Gaco PDS — coats, colours, cure and limitations

Common questions


How many coats do I need?
At least two, to reach the 0.56 mm minimum film. Use alternating colours per coat so you can see full coverage. Lightly textured roofs often need three.
Can I use it on an old felt or asphalt roof?
Yes — but never wash an asphaltic roof first, use White only on aged asphalt (dark colours cause blistering), and prime bleed-prone felt with A4271 Bleed Trap.
Can I walk on it?
Only for occasional maintenance. For regular foot traffic add walkway protection — it is a roof coating, not a deck coating.

Not sure it’s the right product?

Tell 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.

Free Site Survey

Get a Free Site Survey & Quote

Tell us about your building and we’ll recommend the right system — foam, waterproofing or both — surveyed, specified and quoted at no cost.

  • Reviewed by a Duratite specialist
  • No obligation, no hard sell
  • One team from survey to warranty
  • UK-wide coverage
01208 832 602
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