Cut edge corrosion treatment for commercial and industrial metal roofs
Cut edge corrosion is a progressive condition that affects profiled metal roofs across commercial and industrial buildings of all ages. Left untreated, it leads to water ingress at the sheet laps that becomes more expensive to address the longer it is left. Treatment with the Seamsil 100 system arrests the corrosion, re-seals the laps, and extends the working life of the roof without replacing it.
Nova installs the Seamsil 100 cut edge corrosion system made by HD Sharman. The treatment is carried out by trained applicators and backed by HD Sharman's 15-year guarantee.
What is cut edge corrosion?
Profiled metal roof sheets are manufactured with a protective coating applied to the surface. At the cut edges where sheets overlap, that coating is thinner and the exposed steel is more vulnerable. Rainwater collects in the lap joint, sits in contact with the unprotected metal, and corrosion begins.
Over time the rust migrates underneath the upper sheet, creating reverse side corrosion that is invisible from above until it has already caused significant deterioration. Eventually the laps fail to shed water correctly and leaks develop inside the building.
Early stage
Rust staining visible at sheet laps and cut edges. Surface corrosion present but confined to the edge zone. The roof is still watertight but deterioration is under way.
Mid stage
Corrosion has migrated under the upper sheet. Rust-stained water may appear inside the building during heavy rain. Lap joints beginning to open.
Advanced stage
Sheet edges severely deteriorated. Active water ingress. At this stage the cost of treatment increases and in some cases re-roofing becomes the only viable option.
Treatment is most cost-effective at early to mid stage. A Nova survey will assess the current condition and tell you whether treatment is viable and what it will cost before any commitment is made.
How the Seamsil 100 treatment works
Seamsil 100 is a silicone-based remedial system manufactured by HD Sharman specifically for cut edge corrosion on profiled metal roofs. It encapsulates the damaged lap joint area, prevents further water ingress, and protects against reverse side corrosion. The system is UV resistant, remains flexible under temperature movement, and does not require a primer on cleaned and prepared surfaces.
Survey and assessment
The full roof is surveyed to assess the extent and stage of corrosion, confirm the roof structure is sound, and produce a specification for the treatment works.
Surface preparation
Corroded areas are cleaned and abraded to produce a sound substrate. Preparation is the single most important factor in system performance.
Sealant application at laps
Seamsil sealant is gun-applied into the gap between upper and lower sheets, as close to the edge of the upper sheet as possible, forming a complete bridged seal at each lap joint.
Base and top coat application
While the sealant is still wet, the Seamsil base coat is applied to form a fillet and fully encapsulate the leading edge of the top sheet. A top coat follows, completing the system to the specified dry film thickness.
Treat, don't replace
Full re-roofing or overcladding is the right answer in some cases. Cut edge corrosion treatment is the right answer when the roof structure is sound and the corrosion has not progressed beyond the point where the system can arrest it.
Treatment with Seamsil 100
Fraction of the cost of re-roofing. Carried out on the occupied building without disruption to operations below. 15-year HD Sharman guarantee. Works completed in days, not weeks. Extends the roof's working life by 15 or more years.
Re-roofing or overcladding
Appropriate when corrosion has advanced to the point that treatment cannot arrest it, or when the roof requires a full thermal upgrade at the same time. Significantly higher capital cost and programme time.
What the treatment includes
Condition survey
Full roof inspection confirming corrosion stage, roof condition and treatment specification. Carried out before any works are agreed.
Full Seamsil 100 treatment
Preparation, sealant application and base and top coats applied to all specified lap joints, cut edges and vulnerable areas across the roof.
HD Sharman certification
On completion, the installation is certified by HD Sharman's technical team to the standards required for the system guarantee to be released.
15-year guarantee
HD Sharman BBA-backed 15-year product guarantee on the completed Seamsil 100 system. Issued directly by the manufacturer.
Is your roof suitable for treatment?
The Seamsil 100 system is suitable for all types of profiled commercial and industrial metal roofs, including steel and aluminium profile sheeting. It is used across warehouse and distribution roofs, industrial estates, manufacturing facilities, agricultural buildings and any building with a profiled metal roof showing signs of lap joint corrosion.
Visual indicators
Rust staining running down the sheet face below the lap lines. Orange or brown discolouration at sheet overlaps. Visible corrosion at the cut edges of the upper sheets. Rust-coloured water marks on internal walls or ceilings below the roof line.
Building types
Warehouses, distribution centres, industrial units and manufacturing facilities. Commercial and agricultural buildings with profiled steel or aluminium roofs. Any metal roof where the structure is sound but the sheet laps are deteriorating.
Common questions about cut edge corrosion treatment
How do I know if my roof has cut edge corrosion?
The most visible sign is rust staining running down the sheet face below the lap lines, or orange-brown discolouration at the sheet overlaps and cut edges. In more advanced cases, rust-coloured water marks may appear on walls or ceilings inside the building. A Nova survey will assess the extent and stage of corrosion and confirm whether treatment is appropriate.
Can the treatment be carried out on an occupied building?
Yes. The Seamsil 100 system is a cold-applied, solvent-based silicone treatment. There are no hot works, no flame and no requirement to remove roof sheets. Treatment is carried out from above the roofline with no disruption to operations below in most cases.
How long does cut edge corrosion treatment take?
Preparation and application time depends on the roof area and the extent of the corrosion. A standard industrial unit of around 1,000 to 2,000 square metres is typically completed in two to four days once works are under way. We agree a programme before work starts.
What guarantee comes with the treatment?
The completed Seamsil 100 installation is backed by HD Sharman's 15-year product guarantee, issued directly by the manufacturer following certification of the completed works. This is a BBA-assessed system with a proven track record on commercial and industrial roofs across the UK.
What happens if the corrosion is too advanced for treatment?
If the survey establishes that corrosion has advanced beyond the point where Seamsil 100 can reliably arrest it, we will say so and set out the alternatives, typically overcladding or full re-roofing, with costs and options. The survey visit is free and there is no obligation to proceed.
Does the roof need to be replaced instead?
Not necessarily. If the roof structure is sound and the corrosion has been caught at early to mid stage, treatment is typically a fraction of the cost of re-roofing and will extend the roof's working life by 15 or more years. The survey establishes which route is appropriate for your specific roof.
Does treatment work on asbestos cement roofs?
Cut edge corrosion as addressed by the Seamsil 100 system is specific to profiled metal roofs. Asbestos cement roofs present different issues and different treatment options. If your building has asbestos cement roofing, we survey and specify for that separately.
Book a free roof survey visit
If your metal roof is showing signs of lap corrosion, the earlier it is assessed the more options you have. We will survey the roof, confirm whether treatment is viable, and give you the cost in writing. No obligation.
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