Metal Roofing in Duncan

Moss needs something to hold onto. An asphalt shingle's granular surface and lapped edges give it exactly that, which is why roofs in the Cowichan Valley grow moss faster than roofs in Victoria under half the rainfall. A smooth metal panel offers no mat and sheds water before it can sit, so the maintenance interval that governs asphalt largely disappears.

The service life difference follows from that. Forty to seventy years for metal against fifteen to thirty for asphalt is not a marketing spread — it reflects the fact that asphalt fails from sustained wetting and metal does not. On a heavily treed lot toward Sahtlam or Lake Cowichan, where a shingle roof needs treating every few years, metal changes the ownership cost rather than just the look.

Standing-seam panels are held by concealed clips, with the seam raised above the water plane and no fastener penetrating the weather surface. Exposed-fastener profiles are screwed through the panel face into the strapping, each screw sealed by a neoprene washer. Those washers are the system's clock — they harden, shrink and back off, and in sustained coastal wet a twenty-year-old exposed-fastener roof is usually a re-screwing project.

Standing seam costs more and gives back a roof with no gaskets in the water path. It also handles thermal movement better on long runs, which matters on south-facing slopes here. Exposed-fastener panel still earns its place on outbuildings, shops and simple low-value roofs where the price gap is the deciding factor. Either way, the flashing at chimneys, skylights and wall junctions is where a metal roof is actually won or lost.