Asbestos Roof Waterproofing — Eldon Road Trading Estate, Nottingham
From failing roof to finished system
The Challenge
Asbestos cement is stable while its surface is intact. The cement binds the fibres, and an undamaged sheet releases nothing. What undoes it is weather and time — and at Eldon Road both had been at work for decades.
Organic growth had colonised the corrugation troughs, holding moisture against the cement instead of letting it run off. The laps carried a history of bituminous patch repairs, each one an admission that water had found a way in. The GRP rooflights had aged with the sheets around them — and the units below were occupied and trading.
Project file
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The Solution — step by step
Why not simply remove it?
Stripping the roof would have meant licensed asbestos removal, controlled disposal of every sheet, and occupied industrial units exposed beneath a re-sheeting programme. For sheets that were still structurally sound, that is a disproportionate answer — and a far more expensive one.
A fluid-applied silicone overcoat inverts the logic: rather than breaking the material up to carry it away, it seals the roof where it stands. The building owner weighed 10-year and 20-year warranty system options and, with the landlord’s approval secured, committed to the 10-year GacoFlex™ S42 system in early June 2026.
The system
Three stages, applied externally, each dependent on the one before it being right.
- Sollac Hipolava — biocidal wash. The biological growth that holds moisture against the cement is treated and removed, and the roof taken back to a sound, dry substrate. Coating over contamination is how overcoat systems fail, so the clean is the foundation of the warranty, not a courtesy.
- GacoPatch — silicone detailing. Every vulnerable line on the roof — sheet laps, fixing heads and the full perimeter of each GRP rooflight — worked by hand in GacoPatch silicone repair compound before the field coat goes anywhere near the roof. The places water exploits are sealed first.
- GacoFlex S42 — silicone membrane, light grey. A high-solids silicone waterproofing membrane, roller-applied across the full corrugation profile in a single coat at approximately 500 microns wet film, curing into a seamless, UV-stable elastomeric skin over the entire roof.
Why silicone on an asbestos cement roof
A corrugated asbestos cement roof cannot be mechanically overclad without penetrations, and it cannot be patched indefinitely. A fluid-applied silicone membrane suits it precisely because it asks nothing of the sheets: no fixings, no loads, no disturbance — just a cleaned surface to bond to.
GacoFlex S42 is 96.5% solids and solvent-free. Unlike acrylic coatings it withstands ponding water without degrading, and its silicone chemistry is inherently UV-stable — it does not chalk away under sunlight. It is also a renewable system: at the end of its warranted life the roof is cleaned and recoated, and the clock starts again. The asbestos cement underneath never needs to be touched.
The installation
This was a supply-only project delivered through the Duratite Approved Installer network: Duratite Building Products supplied the full Gaco system, the technical specification, coverage guidance and warranty support, and J & B Contract Services Limited — a Duratite Approved Installer — carried out the installation.
Access ran from a mobile elevating work platform at the eaves, with timber crawl boards spreading every load carried on the roof itself — the discipline a fragile asbestos cement roof demands. J & B elected to roller-apply the system rather than spray it: a deliberate choice that eliminated overspray risk on an occupied estate and let the team work the silicone into every trough, ridge and lap line at a controlled pace.
Film build is what a coating warranty stands on, so wet-film comb gauge readings were taken as the application advanced, verifying the build against the approximately 500-micron single-coat requirement for the 10-year system. Every rooflight was perimeter-sealed and left clear, so the units below kept their natural light.
The Outcome
The full roof now sits under one seamless silicone membrane. The weathering that had been working on the cement for decades is arrested, every historic leak path is sealed, and the roof has come off the maintenance list.
Not a single sheet was cut, lifted or removed. No licensed removal, no controlled waste stream, no interruption to the units trading below — the estate barely noticed the roof being given another decade.
Days after completion, Duratite Building Products issued the 10-year manufacturer-backed material warranty on the installed Gaco system to the building’s owner — freely assignable to any successor in title.
On the roof — the full picture
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