How much roof area does one 19 litre pail cover?

Allow approximately 33 square metres per pail for the 10-year specification or 21 square metres per pail for the 20-year specification. Actual coverage varies with substrate condition, texture and application.

Is the 10-year or 20-year system applied in two coats?

The S42 specification uses one continuous coat. The specified application thickness determines the warranty tier. Detailing, preparation and any substrate-specific base coat are separate system steps.

Can S42 be used where water ponds?

Gaco S42 is a 100 percent silicone roof coating designed to withstand permanent ponding water when the roof is correctly prepared and the coating is applied to specification.

What else may be needed with S42?

Clean and prepare the roof first. Seams, fasteners and details require suitable treatment, repairs may require GacoPatch, and asphalt or bituminous substrates may require Bleed Trap. Ask Duratite for a substrate-specific specification if unsure.

What warranty is available?

S42 is available with manufacturer-backed product warranty specifications of up to 20 years, subject to the correct preparation, application rate, system components and warranty requirements.

Gaco S42 Silicone Roof Coating

Overview

GacoFlex™ S4200 is a premium, liquid-applied silicone roof coating engineered to deliver long-term waterproofing protection across a wide range of substrates. This high-performance elastomeric system forms a seamless, monolithic membrane that resists ponding water, UV degradation, and thermal movement. Suitable for restoring flat and low-slope roofs, GacoFlex S4200 silicone roof coating extends roof service life without the need for costly tear-offs.

£325.00 + VAT

Specification

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:

Brush
Roller
Squeegee
Airless Sprayer (contact Duratite for advice)

Property Value

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.

Ready to Specify or Purchase?

Contact our technical sales team for:

Specification support
Fire engineering assessments
Pricing and lead times

Gaco S42 Silicone Roof Coating

Overview

Specification

Application Methods:

Application Equipment:

Surface Preparation:

Recommended Primers:

Topcoat Guidance:

Ready to Specify or Purchase?

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