Cut edge corrosion treatment
Coated steel sheets · ends and laps · treat before perforation
Coated steel roof sheets are cut to length after the coating is applied, which leaves the steel exposed at every cut end. Over time, rust starts there and creeps back under the coating, lifting it, most visibly at the bottom ends of sheets and along end laps. That is cut edge corrosion.
Treated early, by cleaning back, priming and sealing the edges, it can protect sheets for many more years; one maker describes its system as protecting edges for up to 20 years. Left, it perforates the sheets and becomes an overcladding job. Treatment is priced per job.
Signs you have it
Brown staining at sheet ends
Most visible along the eaves and at end laps, where water runs off the cut edge.
Coating lifting or peeling back
The paint or plastisol coating bubbles and peels as rust forms underneath.
Plastisol-coated sheets
The coating most associated with it. It shows sooner on exposed, coastal and polluted sites, and on the side of the roof facing the weather.
Leaks at laps
Once the edge has corroded through, water gets in at the lap.
Options and costs
| Item | Scope | Typical cost |
|---|---|---|
| Cut edge treatment | Clean back, prime, seal tape or coating, topcoat | Per job |
| Full roof coating after treatment | Restores weathering across the whole roof | Per job |
| Overclad if too far gone | New insulated roof over the old | £45 to £65 per m² |
| Strip and re-roof | New sheets on the existing frame | £65 to £85 per m² |
Budget figures read from national price guides and roofers' own published rates in November 2026, shown before VAT. Use them to plan; the contractor's written price is what counts. Work out a budget for your roof.
How treatment works
Preparation
Loose coating and rust are removed from the affected edges, usually back to a sound coating some distance from the edge, by wire brushing or abrasive cleaning. Laps are cleaned out where water and dirt sit.
Priming and sealing
A primer that bonds to both bare metal and the remaining coating goes on, followed by either a flexible tape or a reinforced coating that seals the lap and the cut edge. Some systems add a fibre-filled coat at each joint.
Topcoat
A colour-matched topcoat finishes the treated areas, or the whole roof is recoated if the original coating is chalking or failing generally.
Why timing matters
Treatment protects steel that is still sound. Once sheets have perforated, treatment cannot put back the metal that has gone, and the choice is between replacing sheets, overcladding and re-roofing. Coating specialists say that leaving it untreated multiplies the eventual cost.
Where our information comes from
Prices are typical ranges from published UK contractor price guides and roofing firms' price pages, November 2026.
Rust at the sheet ends? Get cut edge treatment priced by a contractor in your area.
Get contractor quotesHow the job runs
A typical cut edge treatment.
Survey
A contractor walks the roof where it is safe to, or flies a drone where it is not, takes cores on flat roofs and photographs every defect. You get a written report with a recommendation.
Specification and price
A written scope naming the system, the details at edges, outlets and rooflights, the guarantee and the programme, with a fixed price excluding VAT.
Clean back and prime
Edges and laps prepared from safe access, never by standing on rooflights or fragile sheets.
Seal and coat
Tape or reinforced coating, then topcoat, bay by bay.
Handover
A final inspection, photographs, the guarantee certificate, building control completion where it applies, and a note of when the next maintenance visit is due.
Cut edge corrosion questions
What is cut edge corrosion?
- Rust that starts at the unprotected cut ends of coated steel sheets and creeps back under the coating. It is the most common failure on plastisol-coated metal roofs and cladding.
How much does cut edge corrosion treatment cost?
- It is priced per job, by the length of edges and laps treated, access and the system used. We have not found a published per-metre rate we trust. As a comparison point, overcladding a roof that has gone too far costs £45 to £65 per m².
How long does cut edge treatment last?
- Coating makers describe their treatment systems as protecting edges for many years, with one quoting up to 20. Ask for the guarantee length and terms in writing.
Can I just paint over it?
- No. Paint over rust fails quickly. The edge must be cleaned back, primed and sealed with a system designed for it.
Does insurance cover cut edge corrosion?
- Usually not: it is gradual deterioration, which most buildings policies exclude. Leaks it causes may be treated the same way. Check your policy wording.
Read next
- Roof overcladding
When the sheets are past saving.
- Industrial roofing
Metal and panel roofs.
- Liquid roofing and coatings
Recoating the whole roof.
- Roof surveys and maintenance
Catch it early.
Get cut edge treatment priced
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