Metal Roof Cleaning: Safe Methods for Standing-Seam and Corrugated Roofs
Metal roofing is one of the better performers in our wet climate, since its smooth, hard surface gives moss less to grip than porous shingle or tile. But better does not mean maintenance-free. Metal roofs still develop algae streaks, oxidation and staining, especially on the shaded slopes and where debris collects.
Here is how metal roofs are cleaned safely, keeping the finish intact.
What goes wrong on a metal roof
The most common issues are dark algae streaking, a chalky oxidation film on older painted metal, and organic staining where leaves and needles sit in the valleys and against roof features. Moss is less of a structural threat than on shingle, but it still takes hold along seams and in debris-filled valleys.
The finish is the thing to protect. Metal roofs have a factory paint or coating that gives them their colour and corrosion resistance, and the goal of any clean is to remove the growth and grime without harming that coating.
Soft wash, not scour
Metal is cleaned with a soft-wash approach: a suitable detergent is applied to break down the algae and grime, then rinsed at low pressure. Abrasive scrubbing pads and harsh scouring are avoided because they scratch the coating and create the very spots where corrosion later starts.
Walking a metal roof also needs care, since panels can dent and wet metal is slippery, so much of the work is done from the edges and with pole systems where possible. As with any roof, high pressure is unnecessary and risks driving water under the panels and seams.
Keeping a metal roof clean
Because metal sheds growth well, the main maintenance is keeping the valleys and features clear of leaf and needle debris that traps moisture and stains. Trimming overhanging branches and keeping gutters flowing does most of the work.
A metal roof that is cleaned gently and kept clear of debris will generally stay looking good longer than shingle or tile in the same spot. Cleaning is quoted per property based on size, pitch and access.