Ponding water — persistent standing pools on a flat roof — is one of the most common causes of commercial roof failure, and Ireland’s frequent Atlantic rain gives it plenty of opportunity. Most coating chemistries cannot handle sustained ponding. Silicone can. This article explains why, what “ponding-rated” actually means, and what drives the cost of a silicone refurbishment on a roof with drainage issues.
Why ponding destroys most roof coatings
Acrylic coatings absorb water over time, softening the film. PU and PMMA systems tolerate short-term ponding but can delaminate or blister under sustained exposure. Bituminous membranes lift, crack and peel when repeatedly saturated. Even good-quality single-ply membranes (EPDM, TPO, PVC) can see seam failure under chronic ponding.
Ponding is also a structural warning: flat roofs are designed to drain within 48 hours. If yours isn’t, there’s a deflection, blocked outlet or falls problem that any refurbishment needs to address alongside the coating itself.
Why silicone handles it
Silicone is hydrophobic. It does not absorb water. Once cured, the membrane is chemically unchanged by indefinite standing water — no softening, no delamination, no degradation. This is why silicone is the standard topcoat for spray polyurethane foam roof systems in the US, where ponding is common and warranties run to 20+ years.
The “ponding-rated” terminology means the manufacturer explicitly warrants the coating against sustained standing water. GacoFlex S42 is ponding-water rated by Gaco — a differentiator that only some silicone systems carry.
Diagnosing your ponding situation
Before quoting a refurbishment, we want to know:
- How many ponding areas are there, and how deep?
- How long does water sit (hours, days, weeks)?
- Are gutters and outlets clear and functional?
- Is the roof deflected (structural) or just off-level (construction)?
- What’s the underlying substrate condition (saturated insulation, failed membrane)?
Our free site survey captures all of this. For roofs with only off-level ponding (construction tolerance, outlet placement), a silicone coating alone is the fix. For roofs with structural deflection or saturated insulation, the coating needs to come with a remedial scheme — we’ll tell you honestly what we find.
Typical project workflow
- Pressure wash to remove loose debris, algae and contaminants
- Remove standing water (vacuum or allow to evaporate)
- Repair any major deck defects (saturated insulation replaced, failed laps re-welded)
- Apply bleed-trap primer on asphalt/BUR substrates
- Seal seams, penetrations and details with SF42 fibre-reinforced silicone
- Apply GacoFlex S42 topcoat at 1.0 L/m² in a single pass
- Cure for 8-12 hours
- Triple-inspection regime (pre / mid / post) for 20-year warranty tier
Cost for a ponding refurbishment
Every ponding refurbishment is priced per project, with a fixed quote after a free site survey. Compared with a standard silicone supply-and-install on a roof without ponding, ponding adds a modest increment for additional bleed-trap, seam reinforcement and the inspection regime — and any remedial work the survey finds, such as replacing saturated insulation. The existing roof stays in place — no strip-and-replace and no waste to landfill — so the overall cost is typically a fraction of full replacement, and the roof comes out of the process with a manufacturer-backed warranty against future ponding.
Got a roof with standing water? Email info@duratite.ie for a free survey, or see our silicone guide.