Profiled metal roofs — a defining sight of industrial estates, distribution parks and agricultural buildings across Ireland and Northern Ireland — typically start leaking around year 20. Cut-edge corrosion at eaves and verges, pinhole leaks around fasteners, lap failures in wind uplift zones. Strip-and-replace means new cladding, new fasteners, a lot of scaffold and weeks of downtime. Silicone coating fixes everything in one application. Here’s the full picture.
Typical failing metal roof symptoms
- Cut-edge corrosion: Rust bloom along the cut edges at eaves and verges, spreading up the sheet
- Fastener corrosion: Rust pinpricks around every fixing, often with water staining below
- Lap failures: Side and end laps pulling apart or corroding through
- Pinhole leaks: Scattered corrosion through the sheet, invisible from ground
- Paint failure: Original PPGI coating chalked, cracked or peeled — base metal exposed
How silicone fixes all of these
A silicone overcoat system for metal roofs is a two-stage process:
- Detail stage: SF42 fibre-reinforced silicone applied at every cut edge, every lap, every fastener head, every penetration. This adds mechanical reinforcement to weak points.
- Overcoat stage: GacoFlex S42 applied in single pass over the entire roof, sealing pinholes, bridging minor cut-edge corrosion, and forming a seamless waterproof layer.
The result: the metal roof is effectively new again, with a 15 or 20-year manufacturer-backed warranty.
When metal overcoat is appropriate
- Sheet gauge is sound (no sections thin-rusted through)
- Structural purlins and rails are sound
- Fasteners are mostly intact (individual failures can be replaced)
- Gutters and roof lights are separately addressed
When recladding is better
- Sheet is thin-rusted through over large areas
- Purlins or rails are structurally compromised
- Full insulation upgrade is planned
- Change of use requires different profile or thermal performance
Cut-edge corrosion specifically
Cut-edge corrosion is one of the most common failure modes on profiled metal roofs, and Ireland’s wet, windy Atlantic climate gives it every opportunity. The original paint system doesn’t wrap around the cut edge, so water wicks in and rust propagates. By the time you can see it from ground level, it’s often advanced far up the sheet.
The silicone cut-edge treatment is a targeted repair: wire-brush the affected edge, apply a rust-converting primer if needed, then fibre-reinforced SF42 detail, then GacoFlex S42 topcoat. On early-stage cut-edge corrosion, this arrests the process and adds 20+ years of life without touching the rest of the roof. On late-stage, a full roof overcoat is typically the better economic answer.
Cost
- Cut-edge only: priced per linear metre, depending on corrosion severity and access
- Full roof overcoat (15-year warranty): priced per project — fixed quote after a free site survey
- Full roof overcoat (20-year warranty): priced per project, reflecting the triple-inspection regime
- Strip and reclad (comparison): typically several times the cost per m² of an overcoat, depending on profile and insulation
Rusty metal roof? Email info@duratite.ie for a free survey, or see our commercial waterproofing page.