How to Remove Rust from a Metal Roof

early stages rust roof sheet

Removing rust from your metal roof should always be a priority. The presence of any amount of rust is a sign the protective coating has failed. Coatings such as zinc and additional layers of paint on galvanised corrugated steel roof sheets are all vulnerable. Metal roofs suffer most in wet and humid environments. While this is something a competent person can do themselves, we would always recommend hiring a professional contractor to carry out work on any roof-system.

Whether you’re the tenant or owner of a building with a corroded roof, its important to act fast. Small amounts of rust such as staining around fixings can be fixed easily and fast, by yourself. You do of course need to stay safe when working on a roof. Hiring an aerial work platform or ‘cherry picker’ is a good start. You’ll also need a harness and safety line. HSS and Screwfix are just two of the many safety hire and sales outlets to get such equipment.

delamination rust corrugated roof sheet overlap
A serious case or paint delamination due to rust and corrosion on the metal roof sheet at the overlap point. Cut edge corrosion is a serious issue.

Check for rust

If you don’t have a clear view of your roof from the ground it’s easy to forget about it. Not until you see rust stains on your skylights do you realise there’s a problem. By now its too late, you’re going to need a professional roof coating contractor. So a quick check on dry bright day, once or twice a year will save you money. If you have access to your roof from within your premises, great! If not we recommend hiring a cherry picker. Alternatively borrow or hire a drone with a high resolution camera. You’ll have a bit of fun and its safer than going on the roof yourself.

Hotspots to look out for are the areas around the fixings or roof screws and roof sheet overlaps. Pay close attention to the screw heads. They often suffer torque damage during installation when the protective coating is chipped. This lets in moisture. The screw head then suffers from galvanic corrosion and the rust spreads to the surrounding area on the roof sheet. Act fast if you spot any corroded screw heads. Like any rust problem, catching it early with save time and money in the future.

examples metal roof rust
Further examples of rust on steel roofs, left to right, sheet overlap corrosion at the cut edge, ridge cap corrosion and previously treated bolt head suffering from delamination.

Clean the rust

Try to choose a dry day with no more than a light breeze. First take a wire brush and scrub the rust vigorously. Don’t be a afraid if the coating comes away. This means it has been weakened by the rust and needs to be removed anyway. Next clean the area with hot soapy water to remove debris and any grease. Finally take a cloth and dry the area to be treated. There should be no evidence of rust on either the fixings, surrounding roof sheet or cladding.

ridge cap fixings rust protection
Recently treated ridge cap fixings, overlap and screw heads now protected from corrosion.

Apply a protective coating

Use a flexible dedicated coating to treat the exposed metal substrate. Ideally this should be a silicone based paint. It will better withstand movement in the roof. The screw heads on the roof fixings should be coated regardless. This will protect them against rust in the future. We recommend Seamsil 400 or Giromax. Another high quality coating system we recommend is RoofLock. There are of course many others available from brands such as Tikkurila and AkzoNobel.

Carefully read the paint manufacturers instructions. Apply one or two coats generously to the affected area. Ensure no substrate is left exposed and all screw heads are capped with at least one coat of paint. This will prolong the lifespan of the roof fixings and corrugated sheets and prevent further deterioration.

In summary

  • Carry out regular checks on your metal roof
  • Act immediately on the first signs of rust
  • Ensure all rust is completely removed
  • Apply recommended protective coating
d and d coatings van rear

Hire a professional roof coating contractor

Here at D&D Coatings we are passionate about combatting corrosion. We have decades of experience treating the metal roof systems of commercial premises. Save yourself time and risk of injury, call us for a quotation on 01606 554040 or visit our contact page.

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