A Conway Properties Group company

Commercial roof waterproofing that goes over the roof you already have.

Cold-applied GacoFlex silicone coating systems that waterproof commercial, flat and asbestos-cement roofs in place, with no tear-off, no hot works, and a manufacturer-backed warranty of up to 20 years.

Book a free roof survey Work out what I need

20yr

Manufacturer-backed warranty

One coat

Single-pass silicone system

No tear-off

Coated over the existing roof

UK-wide

Survey, supply and install

One coat, cold applied

A liquid membrane, not a new roof.

GacoFlex silicone is rolled, brushed or sprayed straight onto the existing roof and cures into one seamless, fully bonded membrane, with no laps, no joints and no mechanical fixings left to fail. The building stays open, there is no torch and no open flame, and nothing goes in a skip.

01GacoFlex S42 siliconeSeamless, UV-stable, ponding-rated membrane
02SF4200 SeamSeal detailingLaps, fixings, upstands and penetrations
03Prepared substrateWashed, patched and dried, with no tear-off
04Existing roof deckMetal, felt, single-ply, concrete or cement fibre

What we coat

Three roofs that cost building owners the most.

Profiled metal roof on a commercial building, with rooftop ventilation units

Commercial Roof Waterproofing

Warehouses, factories and industrial units

A seamless, fully bonded silicone membrane rolled or sprayed straight over the roof you already have. It bonds to profiled metal, felt, single-ply and concrete, so there is no tear-off, no re-sheeting and no need to close the building while we work.

Restore the existing roof instead of stripping and replacing it
Cold-applied over a live building, so no downtime for tenants or production
Seals laps, fixings and upstands, which is where commercial roofs actually leak
Recoatable at end of life, silicone on silicone

Flat commercial roof carrying air handling plant behind a parapet

Flat Roof Waterproofing

Felt, asphalt, single-ply and concrete decks

Silicone does not re-emulsify in standing water, which is the failure mode that finishes off acrylic coatings on flat roofs. Ponding areas are exactly where a GacoFlex system belongs, and our warranties cover ponding water for the full term rather than excluding it.

Rated for permanent ponding water, with no standing-water exclusion clause
One coat over tired felt, asphalt, torch-on, EPDM and single-ply
No joints, laps or mechanical fixings left to fail
Ideal substrate for a rooftop solar array

Weathered corrugated cement fibre roof sheets with moss and plant growth

Asbestos Roof Waterproofing

Encapsulate in place, with no removal and no licensed strip-out

Failing asbestos-cement sheets are sealed and waterproofed from above. The coating locks in surface fibres and shields the sheet from UV and moisture, extending the life of the roof without cutting, drilling or the cost and disruption of a licensed removal.

No intrusive removal, no skips of notifiable waste
Locks in surface fibres and stops further weathering of the sheet
Waterproofs and re-lives the roof in a single operation
A fraction of the cost of strip-out and re-sheeting

Solar & flat roofs

Coat the roof before the panels go on it.

A rooftop solar array has a design life of twenty-five years. The flat roof underneath it rarely does. Once the mounting frames, ballast and cabling are installed, that roof is effectively sealed off, and stripping and replacing it means taking the whole array down first, at a cost that can exceed the roof works.

Coating it first solves that. A GacoFlex silicone membrane goes on in a single pass before installation, brings the roof's remaining life up to match the array, and is rated for the ponding water that collects around ballast and frames. The white finish also reflects rather than absorbs solar load, so the roof surface runs cooler under the panels.

Match the roof's life to the array's warranty
Ponding-rated around ballast and frames
Reflective white finish keeps the deck cooler
Seamless, with no laps beneath a fixed array

Large distribution warehouse roofs covered in rooftop solar panels, seen from the air

Specifying a rooftop PV scheme?

Talk to us before the array is designed, not after it is installed. We survey the deck, specify the build to suit the mounting system, and programme the coating so it is cured and signed off before the panels arrive on site.

Talk to the technical team

How a job runs

Four phases, signed off at each one.

Substrate Preparation

Mechanical surface scrub with GacoWash concentrated cleaner to lift atmospheric pollution, heavy surface oils and structural oxidation, followed by a power-wash rinse to a clean, sound finish.

Detail Profiling

Heavy detailing over every seam boundary, mechanical anchor, flashing line and upstand using high-solids GacoFlex SF4200 SeamSeal. It is fibre-reinforced, so there is no separate mesh or scrim to bed in.

Waterproofing

Uniform deployment of GacoFlex S42 Series 100% silicone across the cleared field roof area, applied by spray, roller or brush to a verified dry film thickness.

Site QA & Sign-Off

Independent site audit, core sample inspection, adhesion verification testing and formal commissioning of the manufacturer-backed guarantee.

The system

Three GacoFlex products, one silicone chemistry.

Clean, detail, repair, then coat. Because every stage is the same chemistry, the roof cures as a single membrane rather than a stack of dissimilar materials that move against each other.

S42 SeriesField coat

GacoFlex S42 Silicone Coating

The 100% silicone, solvent-free membrane that does the waterproofing. A single-coat system at 96.5% solids that survives ponding water, stays UV-stable instead of chalking off, and bonds direct to most substrates without a primer. Supplied in S4200 White for maximum solar reflectance or S4222 Grey.

Chemistry: 100% silicone, 96.5% solids
Application: Single coat, by spray, roller or brush
Ponding water: Permanently rated, no exclusion
Warranty: Up to 20 years

SF4200Detailing grade

GacoFlex SF4200 SeamSeal

Ultra-high-solids fibre-reinforced silicone for laps, seams, upstands, penetrations and fixing heads. The reinforcement is built in, so it bridges seams, nuts and bolts in a single thick pass without splitting or shrinking, and without the labour of polyester scrim.

Coverage: 1.0 – 1.2 litres per linear metre
Application: Stiff nylon brush or heavy putty knife
Skin time: 2 – 4 hours
Full cure: Within 24 hours

GacoPatchRepair grade

GacoPatch Flashing Compound

Heavy-viscosity, fibre-reinforced trowel-grade silicone for deep splits, valley cracks, voids, punctures and bolt heads. It bonds to damp surfaces and forms a rainproof barrier as soon as it is spread, so an active leak does not have to wait for a dry week.

Use: Splits over 6mm, voids, active leaks
Application: Trowel or high-density squeegee
Substrate: Bonds to damp surfaces
Rainproof: Immediately on spread

Preparation

GacoWash Concentrated Cleanser

A biodegradable mechanical wash that lifts deep-set organic growth, residual greases and surface chalking. Applied by low-pressure sprayer and agitated with a stiff broom, then rinsed and dried completely before any coating goes on.

Warranty

Ponding water is covered, not excluded.

Conventional acrylic and polyurethane elastomeric membranes carry rigid exclusion clauses for standing water. GacoFlex S42 silicone is chemically inert to it. Under continuous immersion it will not degrade, soften or peel, so ponding is covered for the full term of the certificate. Film build alone decides the tier.

10-Year

Light Trade

Minimum 18 mil / 0.45mm dry film thickness

Validation: Visual inspection protocol and basic adhesion sweep.
Approved scope: Standard flat roof renovations and smaller commercial outbuildings.

20-Year

Elite Commercial

Minimum 34 mil / 0.86mm dry film thickness

Validation: Field core-cut analysis, certified pull-tests and a full field thickness trace, signed off by a Sollus certified installer.
Approved scope: High-spec institutional structures and tier-one developer assets.

Materials calculator

How much will my roof take?

Worked out the way our estimators do it. Plan area, pitch and the corrugation profile give the developed area the coating actually has to cover, and the film build gives the pail count.

Roof plan area

m²

The area on the drawing. We work the rest out from the roof build-up.

Roof type

Existing covering

Asphalt oils bleed through silicone and stain it, so a bleed-trap base coat is added.

Warranty build

Area derivation

500 m² plan area

= 500 m² to coat

Your materials

GacoFlex S42 silicone coating
20-Year build at 34 mil / 0.86mm, approx. 21 m² per pail
24 × 19L pail
GacoFlex SF4200 SeamSeal
Laps, fixings, upstands and penetrations. Fibre-reinforced, so no separate mesh
3 × 19L pail
GacoPatch flashing compound
Fill splits, voids and bolt heads before coating. Bonds to damp surfaces
1 × tub
GacoWash concentrated cleanser
Substrate preparation. Diluted, agitated and rinsed before any coating
2 × container
GacoFlex A4271 Bleed Trap base coat
Locks in asphalt oils so they cannot stain the silicone. Required over aged felt
12 × 19L pail

Send this to us for a fixed price

Indicative quantities for budgeting, not a quotation. Access, substrate condition and the detailing schedule all move the figure, so every job is confirmed on a free site survey before anything is ordered.

Book a survey

Free commercial roof survey.

Substrate, ponding, cut edges, access and drainage, all surveyed by our technical team, then written up as a specification and a fixed price. No obligation, nothing owed if you go elsewhere.

Sollus Waterproofing UK is a Conway Properties Group company. Surveys, specifications and installation are carried out by the group's own teams and certified installers.