Moss Removal in Duncan, BC

Duncan sits on the floor of the Cowichan Valley, and that position is most of the story when it comes to moss. This is among the mildest and warmest parts of Canada, and it is also wet — long grey stretches from October through March, then a dry summer. Moss does not need a hard winter to thrive. It needs exactly what the valley bottom hands it: months of cool damp air, shelter, shade, and surfaces that never fully dry out between rains.

Two kinds of Duncan house, two kinds of moss problem

The old townsite core is compact — Duncan is the smallest city by area in Canada — and it is full of mature street trees. Those trees are why the downtown blocks are pleasant to walk, and they are also why the roofs behind them are furred green along the lower third. Bigleaf maple and cedar drop debris straight onto the shingles, the debris holds water, and moss establishes in it rather than on clean roofing. On older homes with shallow pitches and shaded north walls, the growth usually starts at the gutter line and works its way up.

Out on the slopes around town, the newer subdivisions show a different pattern. Roofs are steeper and more open, so the whole surface sheds and dries faster, but wherever a neighbour's fir hangs over a corner or a hip runs down into a valley, moss takes hold and spreads from that point. It also goes unnoticed for longer, because from the street the roof looks fine and the growth is all on the back slope.

What actually gets done up there

Asphalt shingles are never pressure washed. Blasting a shingle strips the mineral granules that protect it from UV, and that takes more life off the roof than the moss would have. The moss comes off by hand, the roof is treated, and the remaining growth dies back and weathers off over the following months. That sequence is the correct one and it is the one we follow, on every roof.

Gutters matter as much as the roof surface. Moss debris fills them, and a blocked gutter pushes water back under the roof edge and down the fascia, which is how a moss problem quietly turns into a rot problem. Left long enough, moss also wicks water in under the shingle edges and lifts them, and freeze-thaw cycling through the winter prises them further apart until water gets past.

The rest of the property

The same conditions work on the ground. Shaded concrete paths and driveways in the older parts of town go green and slick through the winter, and on any sloped approach that is a slip hazard rather than a cosmetic issue. Window frames are worth checking too — the moss and grime sit in the channels, sills and weep holes rather than on the glass, and a blocked weep hole holds water against the frame.

Duncan is our base. It is Quw'utsun' territory, the City of Totems, and the hub the rest of the valley runs through. We are local, hardworking, licensed and insured — get in touch and we will come and look at what is growing on your roof.