Duratite uses a seven-stage process on every asbestos cement roof waterproofing project, regardless of size. The steps are the same whether the job is 300 m² or 30,000 m² — the only thing that changes is the programme duration. This article takes you through each stage in detail so you know exactly what to expect, what the contractor is doing at each point, and what the deliverables are.
Overview of the Seven Stages
| Stage | Duration (per 1,000 m²) | Output |
|---|---|---|
| 1. Survey and quote | 1 day on site | Written quote, RAMS draft |
| 2. RAMS and mobilisation | 1 day pre-start | Signed RAMS, access plan |
| 3. Biocide clean | 1–2 days | Clean, sound substrate |
| 4. Repair and GacoPatch | 1–2 days | Sealed cracks and fixings |
| 5. GacoPrime primer | 1 day | Primed roof area |
| 6. Two coats S42 | 3–4 days | Full waterproof membrane |
| 7. Inspection + handover | 1 day | Warranty certificate, O&M |
Stage 1 — Survey and Quote
Before any work is priced, a Duratite surveyor visits the site. The survey covers: roof area and elevations, sheet condition, biological growth, previous repairs, access requirements, rooflights and penetrations, gutter condition, and structural integrity. Adhesion pull tests may be performed on borderline roofs. The surveyor photographs every elevation and records notes against a project map.
A written quote is returned within five working days, itemised by scope element, with a recommended system and warranty position. The quote references the RAMS framework that will apply to the work.
Stage 2 — RAMS and Mobilisation
Once the client signs off the quote, Duratite issues the site-specific Risk Assessment and Method Statement (RAMS), access plan, and welfare arrangements, and the HSA is notified where required at least 10 days before work starts. The client signs off the RAMS, confirms any operational constraints, and agrees a start date. Access equipment (MEWPs, scaffold, roof ladders) is booked and delivered ahead of the team.
Stage 3 — Biocide Clean
On day one of works the roof is washed with a low-pressure biocide solution that kills off moss, lichen and algae while chemically cleaning the cement surface. Crucially this is a low-pressure process — never high-pressure jet-washing, which would release fibres. Wash water is captured and routed through gutters to a controlled collection point where required. After cleaning, the roof is left to dry completely before the next stage.
Why Biocide Not Jet Wash?
The position is unambiguous — high-pressure water jetting of asbestos cement releases fibres and must never be used on an asbestos roof. Duratite's biocide process removes growth chemically over 24–48 hours without touching the surface.
Stage 4 — Repair and GacoPatch
Every crack, hole, elongated fixing and detail area is inspected and repaired. GacoPatch is brushed into cracks and covered with fibreglass scrim where bridging is needed. Fixings are over-coated and flashed. Ridge caps, rooflight upstands, and penetrations all receive reinforced detailing at this stage. A project map records every repair location for the warranty pack.
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Stage 5 — GacoPrime Primer
GacoPrime is a penetrating primer specifically formulated for aged asbestos cement. It soaks into the porous substrate, locks any remaining surface fibres, and provides the chemical bond between the substrate and the top coat. Primer is applied by roller or low-pressure airless spray across the whole roof area, including repaired zones, and allowed to cure for the specified window before the top-coat goes on.
Stage 6 — Two Coats of GacoFlex S42
The main waterproofing layer is GacoFlex S42, a fibre-reinforced silicone. It is applied in two coats at right angles to each other (cross-hatched application) to ensure full coverage and eliminate pinholes. Total dry film thickness is typically 0.6–0.8 mm and wet film readings are taken during application and logged on the project map.
Why Two Coats?
One heavy coat tends to sag and leaves pinholes in corrugations. Two medium coats at right angles give a consistent thickness and bridge every micro-defect, which is why the 20-year warranty holds up. Duratite never cuts this to one coat even on smaller projects.
Weather Windows
S42 needs surface temperatures above 5°C and a dry application window of at least 2 hours. Duratite site managers monitor forecasts hour-by-hour during application and will stop work if conditions change.
Stage 7 — Inspection, Warranty, Handover
On the last day of works the project supervisor walks the roof with the client (or a photographic hand-over for clients who prefer not to go to roof level), verifies all areas are fully coated, confirms no missed details, and releases the project to the warranty team. The warranty certificate is issued, the O&M manual with photographs and wet-film records is handed over, and the site is demobbed.
Quality Control Throughout
Every Duratite project has a named project supervisor on site throughout the works. Daily records include: weather conditions, application rates, material batch numbers, wet-film thickness readings, and photographs. This gives a full audit trail that supports the 20-year warranty and can be produced on request years later if any question ever arises.