In this article
A metal cladding roof rarely fails all at once. The protective coating chalks, the colour fades to a patchy grey, and small spots of red oxide show through where the original paint has worn thin. Left alone, that surface corrosion spreads and the panels themselves start to suffer. This warehouse unit roof had reached exactly that point when we were asked to bring it back.
The brief was straightforward but the access was not. The client wanted the roof restored to a clean, uniform colour and protected against further weathering, without the cost and disruption of replacing the cladding sheets. A full respray was the sensible answer; the challenge was doing it well on a profiled steel roof, at height, in a Surrey weather window that does not stay dry for long.
What the roof needed before any paint went on
On a cladding respray, preparation is most of the job. Spraying fresh coating over a dirty, chalky or rusting surface is the surest way to get a finish that peels within a season. Our commercial spray painting team worked through the roof methodically before a drop of SMP was opened.
- Thorough cleaning to strip off years of atmospheric grime, algae and the chalky residue of the failed coating.
- A biocidal wash to kill off algae and lichen so they cannot push back through the new film.
- Spot treatment of corrosion, taking back any loose oxide and treating bare metal so rust does not creep under the new paint.
- Priming where the substrate had been exposed, giving the topcoat a sound, consistent surface to bond to.
Getting this stage right is the difference between a coating that lasts and one that simply hides the problem for a year. The same principle applies to almost every job we take on, which is why we always cover how proper surface preparation underpins a lasting finish with clients before we quote.
Before and after
The before shot tells the story: a tired, uneven roof with the original colour all but gone. The after shot is a clean, consistent sheet of fresh coating across the whole run of cladding.
Why we chose SMP paint
Not every paint belongs on a metal roof. For this job we used a silicone-modified polyester (SMP) coating, the same family of product used to factory-finish cladding panels in the first place. That matters: you are re-coating with something compatible, not a household exterior paint pressed into a job it was never made for.
SMP earns its place on cladding for a few practical reasons:
- Adhesion to metal. It is formulated to bond to galvanised and pre-finished steel, so it grips rather than sits on the surface.
- Colour and gloss retention. It holds its colour far better than a standard coating, resisting the chalking and fading that wrecked the original finish.
- Weather resistance. It stands up to UV, driving rain and the freeze-thaw cycles a Surrey winter throws at an exposed roof.
- Flexibility. Metal expands and contracts with temperature, and SMP moves with it instead of cracking.
Choosing the right coating for the surface and the exposure is a decision we take seriously on every exterior job, whether it is a roof like this or the masonry and joinery covered in our guide to picking exterior paint for Surrey's climate.
Spraying the roof
With the surface sound, the coating went on by spray rather than brush or roller. On a large profiled roof, spraying is the only sensible way to lay down an even film into every rib and valley of the cladding, with no brush marks and a consistent build across the whole area. Edges and details were cut in carefully, then the open runs were sprayed in passes to an even thickness.
Working on a roof brings its own considerations beyond the paint itself: safe access, protecting the building and anything below from overspray, and timing the work around the weather so each coat cures properly. These are the everyday realities of exterior painting work on a commercial scale, and they sit alongside the access and site rules we set out in our overview of commercial painting regulations in the UK.
The result is a roof that looks reset rather than patched, with a uniform colour and a coating designed to keep performing for years. It is the same approach we bring to interior commercial work too, such as the interior woodwork we spray for commercial clients.
Have a tired warehouse roof, factory cladding or another commercial surface that needs reviving? We cover Surrey and South West London for jobs of every size. Tell us what you have in mind for a free, no-pressure quote and we'll talk you through the right approach.
