Cut Edge Corrosion Treatment Ireland

What Is Cut Edge Corrosion?

When profiled metal roof sheets are manufactured, they are coated with a protective finish — typically plastisol, polyester, or PVDF. This coating protects the flat surfaces of the sheet, but at the cut edges (where sheets are trimmed to size, lapped, and fixed), the bare metal is exposed. Over 10–20 years, moisture attacks these unprotected edges, and corrosion begins to eat into the metal at every sheet overlap. The corrosion is often invisible from ground level because it occurs in the concealed lap between sheets. By the time you see rust staining on the underside of the roof, the damage is already extensive.

Cut edge corrosion is not just a cosmetic issue. As the metal corrodes, it swells and lifts the sheet laps apart, creating gaps that admit rainwater directly into the building. The corroded metal weakens, fixings lose their grip, and the structural integrity of the roof cladding is compromised. On large industrial buildings, cut edge corrosion can affect hundreds of metres of lap joints simultaneously.

How We Treat It

Duratite's cut edge corrosion treatment uses GacoFlex liquid-applied coating systems to permanently seal corroded lap joints and restore the waterproof integrity of the roof. The treatment involves three stages: cleaning and preparation of the affected areas, application of a rust-inhibiting primer to stabilise the corrosion, and application of a flexible GacoFlex coating that bridges the lap joint and creates a permanent waterproof seal. The coating maintains flexibility through thermal cycling, so it moves with the metal without cracking — unlike rigid sealants that split and fail.

Cut Edge Corrosion — GacoFlex liquid coating application

Where Cut Edge Corrosion Occurs

Sheet Lap Joints

The horizontal overlaps where roof sheets are lapped are the primary location for cut edge corrosion. Every lap joint on the roof is a potential failure point as the factory coating breaks down at the exposed edges.

Ridge Caps

Ridge cap flashings at the roof apex are exposed to maximum weather and UV. The cut edges where ridge caps overlap roof sheets corrode faster than lower positions on the roof.

Valley Gutters

Valley gutters collect and channel large volumes of rainwater. The constant moisture contact accelerates corrosion at the gutter edges and where gutter sections are jointed.

Verge & Eaves Details

The edges of the roof at verges and eaves are exposed to wind-driven rain and lack the shelter of adjacent sheets. Corrosion at these positions is often the earliest to develop.

Around Fixings

Roof fixings penetrate the metal sheet and create a point where moisture can enter. As sealant washers degrade, water tracks around the fixing and corrodes the surrounding metal.

Flashing Overlaps

Where flashings overlap roof sheets at walls, parapets, and penetrations. The trapped moisture between the flashing and sheet accelerates corrosion in these concealed locations.

Why Choose GacoFlex

Stops Corrosion Progressing

The rust-inhibiting primer stabilises existing corrosion, and the GacoFlex coating seals the lap joint from further moisture contact — permanently halting the corrosion process.

No Roof Replacement Needed

Treatment is applied to the existing roof in situ. No sheet removal, no re-cladding, no scaffold towers, no crane lifts. The roof stays in place and the building stays operational.

Flexible — Moves With Metal

GacoFlex maintains flexibility from -40°C to 90°C. It expands and contracts with the metal through thermal cycling — unlike rigid sealants and mastic tapes that crack and fail within years.

20-Year Warranty

Treatments using the full GacoFlex system are backed by manufacturer warranties of up to 20 years from Gaco. Far longer than any mastic tape or caulk repair.

Can Treat Full Roof

If cut edge corrosion is widespread, the entire roof can be coated — treating all lap joints, fixings, and details simultaneously. This provides full waterproofing plus cut edge treatment in one programme.

Keeps the existing roof in place

Treating cut edge corrosion costs a fraction of full roof replacement and is priced after a free site survey. Treatment extends roof life by 20+ years.

GacoFlex Coating vs Roof Replacement

See how liquid-applied roof coating compares to traditional roof replacement for commercial and industrial buildings.

Factor	GacoFlex Coating	Full Roof Replacement
Cost	Priced after a free site survey	New roof, strip-out and disposal
Typical Duration	5–10 days	4–8 weeks
Business Disruption	None	Significant
Scaffold Required	Rarely	Always
Manufacturer Warranty	Up to 20 years	10–15 years typical
Ponding Water Resistant	Yes (silicone)	Depends on membrane
Existing Roof Removed	No	Yes
Waste to Landfill	Minimal	Significant
Renewable at End of Life	Yes — recoat over existing	Full replacement again

Real Results

See the difference GacoFlex coating systems make on real roofs. Every project includes a free survey, detailed specification, and 20-year warranty.

Worker applying cut edge corrosion treatment to metal roof lap joints

Completed cut edge corrosion treatment — sealed lap joint

Profiled metal roof sheets after cut edge corrosion treatment

Sealed drip edge after cut edge corrosion treatment — fully waterproof

How It Works

Free Roof Survey

Our technical team inspects your metal roof and maps the extent of cut edge corrosion across all lap joints, ridge caps, gutters, and details. We photograph affected areas and assess whether localised treatment or full roof coating is needed.

Specification & Quote

Based on the survey, we specify the optimal treatment approach — localised cut edge treatment for early-stage corrosion, or full roof coating for widespread damage. Fixed-price quotation with no hidden costs.

Clean & Prepare

Corroded lap joints are cleaned back to sound metal using wire brushing and mechanical preparation. Loose material, rust scale, and failed sealants are removed. The prepared edges are primed with a rust-inhibiting corrosion primer.

GacoFlex Coating

A flexible GacoFlex coating is applied over the primed lap joints, bridging the overlap and creating a permanent waterproof seal. For full roof treatments, the coating extends across the entire roof surface including all fixings and details.

Inspection & Warranty

Every treated joint is inspected for coverage and adhesion. Your manufacturer warranty is registered with GacoFlex (an Amrize brand). Maintenance guidance is provided to maximise the treatment's service life.

Frequently Asked Questions

Cut edge corrosion treatment costs depend on the extent of the damage and whether localised treatment or full roof coating is required. Localised cut edge treatment is priced per linear metre of affected lap joint; full roof coating (which treats all cut edges as part of a complete waterproofing system) is priced per square metre. Both are priced after a free site survey and are significantly cheaper than roof replacement.

Common signs include: rust staining visible on the underside of roof sheets at lap joints; brown or orange discolouration along the lines where sheets overlap; water dripping at regular intervals along the lap line during rainfall; flaking or bubbling paint at sheet edges visible from the roof surface. If your profiled metal roof is more than 10 years old, cut edge corrosion is highly likely. Duratite provides free roof surveys to assess the extent of the problem.

Yes — when treated with the right system. Traditional repairs using mastic tape, butyl sealant, or rigid caulk typically fail within 2–5 years because they cannot accommodate the metal's thermal movement. GacoFlex flexible coating maintains its integrity through decades of thermal cycling, providing a permanent repair backed by a 20-year manufacturer warranty.

For the vast majority of metal roofs with cut edge corrosion, treatment is far more practical and cost-effective than replacement. Treatment costs 50–70% less, takes days rather than weeks, requires no scaffold or crane access, and keeps your building operational. Replacement is only necessary when the metal substrate has lost structural integrity — which is rare if cut edge corrosion is caught and treated in time.

Cut edge corrosion treatment with GacoFlex systems is backed by manufacturer warranties of up to 20 years. The flexible silicone coating does not crack, peel, or become brittle over time, and it permanently resists moisture contact at the treated joints. At end of warranty, a maintenance recoat can extend protection further.

The preparation stage (cleaning and priming) requires dry conditions, but GacoFlex silicone coating becomes rain-resistant within 2–4 hours of application. Your approved contractor will schedule around weather windows. For emergency leak repairs at corroded joints, GacoPatch silicone sealant can be applied even in active rainfall to provide an instant-cure temporary seal.

Cut edge corrosion is caused by the breakdown of the factory-applied coating at exposed metal edges — particularly at sheet laps where sheets are trimmed and overlapped. Moisture enters the unprotected edge, reacts with the bare steel, and corrosion begins. UV radiation, atmospheric pollution, salt air (in coastal areas), and thermal cycling all accelerate the process. It is an inevitable consequence of ageing on all profiled metal roofs.

Yes. Farm buildings, livestock housing, grain stores, and agricultural sheds frequently suffer from cut edge corrosion — often accelerated by ammonia from livestock and high humidity levels inside the building. GacoFlex coating is chemically resistant to these conditions and provides long-lasting protection for agricultural metal roofs.

Mastic tape and butyl sealant strips are a common but short-term fix for cut edge corrosion. They typically fail within 2–5 years because they cannot accommodate the metal's thermal expansion and contraction — the tape lifts at the edges as the metal moves, admitting water behind the repair. GacoFlex flexible coating bonds permanently and moves with the metal, providing a repair that lasts decades rather than years.

It depends on the extent of the corrosion. If cut edge corrosion is localised to a few lap joints and the rest of the roof is in good condition, localised treatment may be sufficient. However, if corrosion is widespread across many laps, or if the roof has other issues (leaking fixings, failed sealants, general weathering), a full roof coating is more cost-effective and provides comprehensive protection. Duratite's free roof survey will determine the best approach for your building.

Cut Edge Corrosion Treatment