A leaking asbestos cement roof is one of the most common calls Duratite receives from facilities managers, especially after Atlantic winter storms. The temptation is to patch it with bitumen or silicone and hope for the best — but on an asbestos substrate that approach usually makes things worse, damages the sheets further, and creates a maintenance liability. This guide walks through what to do in the first 24 hours, how to stabilise the roof safely, and how to arrange a permanent solution that holds for 20 years.
Why Asbestos Roofs Start Leaking
Asbestos cement sheets were designed for a 30–40 year service life. Most AC roofs in Ireland and Northern Ireland are now well past that. Leaks typically start at one of five points: fixing holes where the sheet has elongated around the bolt, hairline cracks from thermal movement, end laps where sealant has perished, ridge and eaves flashings, and around rooflights. On older roofs the surface has also delaminated — the cement matrix has eroded and the remaining sheet is more porous than it looks.
Immediate Steps to Take
When water first appears inside a commercial building, the priority is protecting stock and staff — not climbing onto the roof. Follow these steps in order:
1. Move stock and electrical items away from the drip zone.
2. Place buckets or drip trays with a catch area at least 50% larger than the visible wet patch.
3. Photograph the damage and note the exact location (column reference, bay number).
4. Check the roof from below with binoculars — do NOT walk on an asbestos roof unless you have proper roof ladders and PPE.
5. Call a specialist. On a commercial building the cost of stock damage usually dwarfs the cost of emergency attendance.
Temporary vs Permanent Repairs
There is a real difference between stopping a leak today and fixing the roof properly. Temporary repairs buy time; permanent encapsulation gives a 20-year warranty. Both have their place.
| Approach | How Long It Lasts | Relative Cost | Warranty |
|---|---|---|---|
| Tape over rooflight joint | 3–6 months | Very low | None |
| Targeted GacoPatch repair | 2–4 years | Low | 2 years |
| Localised S42 over-band | 5–8 years | Moderate | 5 years |
| Full encapsulation (S42) | 20+ years | Highest upfront, lowest per year | 20 years |
Emergency Repair Options
GacoPatch Targeted Repairs
GacoPatch is a brushable polymer patch designed for asbestos cement. It bonds to aged AC without releasing fibres and can bridge small cracks and holes. Duratite emergency crews carry GacoPatch kits and can normally seal a localised leak within 2–3 hours of arriving on site.
Scrim-Reinforced Over-Bands
Where a crack runs across a full sheet or down a corrugation valley, Duratite will lay a fibreglass scrim in a bed of GacoFlex S42 and cap it with a second coat. This gives a durable repair that lasts several years and buys time before a full encapsulation programme.
Temporary Sheeting
In rare cases — a full sheet has fractured, or there is structural damage — a temporary tarp and timber frame may be needed to stabilise the roof until a proper repair can be scheduled. This is always a last resort.
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The Permanent Fix: Full Encapsulation
Once the emergency is under control, the real question is when to schedule full encapsulation. If the roof is already leaking in one area, the rest is not far behind. A full GacoFlex S42 system with GacoPrime primer, two coats across the whole area, and reinforced detail work at laps and flashings gives a 20-year warranty and eliminates the drip-tray-and-panic cycle permanently. Most facilities managers find the maths compelling once they add up six months of emergency call-outs plus ruined stock.
For a step-by-step explanation of how Duratite delivers the full process, see the full process guide.
Repair Costs and Timelines
Every leak is priced on what the survey finds, so Duratite does not publish a price list. As a guide to relative cost, emergency attendance and targeted GacoPatch repairs are the smallest outlay, localised over-banding sits in the middle, and full encapsulation is the larger capital project — though still typically a fraction of the cost of full roof replacement. On timelines, a targeted patch is usually completed within hours of arriving on site, and a 1,000 m² warehouse takes around 7–10 working days to encapsulate fully. You receive a fixed quote after a free site survey.
When to Call a Specialist
As soon as water appears inside the building. Asbestos cement roof leaks do not self-heal and will progress rapidly once the cement matrix breaks down. Email Duratite at info@duratite.ie — we coordinate repairs through our approved installer network across Ireland and Northern Ireland and can usually arrange attendance within 48 hours of a call.