Roof Moss Removal in Nanaimo, Done by Hand

Why roofs here grow so much of it

Nanaimo sits in the Coastal Douglas-fir zone, and most of its rain arrives between October and March. Through those months a shaded roof barely dries between showers. Douglas fir, western red cedar and bigleaf maple shade the shingles and drop needles and leaves that trap even more damp in the low spots. The dry summer turns moss brown and crisp, but it does not kill it. The first steady rains of fall bring it straight back to green.

Growth follows the shade. The north-facing pitch, the slope under an overhanging branch, the valleys where two roof planes meet and the bottom few courses where debris washes down are where it starts and where it gets thickest.

What moss does to a roof over a few winters

It keeps the shingles wet

A clean shingle roof sheds a downpour in seconds and dries within hours of the rain stopping. A cushion of moss soaks up rain and stays wet for days. That constant damp softens the edges of asphalt shingles, works into the grain of cedar, and gives the next generation of spores an ideal bed.

It pries up the overlap

Every roof depends on each course lapping over the one below it, so water runs across the surface and never gets behind it. Moss grows into the small gap at the lower edge of each shingle. As the clump thickens it pushes that edge upward, and the overlap that keeps the roof dry starts to open. Wind can then catch the raised edge, and driving rain gets underneath.

Frost widens the gap

The coast is mild, but Harewood and the higher streets toward the mountain still see a run of freezing nights most winters. Water held in a lifted edge freezes, expands, and pushes the gap a little wider. When it thaws, more water runs in, and the next cold night repeats the cycle. Over a winter or two that can expose nail lines and the felt underneath, and the first sign indoors is often a stain on a ceiling long after the problem began.

It ends up in the gutters

Moss sheds clumps every time it rains hard, and they wash down into the eavestroughs, where they knit into needle mats and block the downspouts. An overflowing gutter can push water back under the starter course and onto the fascia board. Taking the moss off the roof stops that supply at the source, and the clumps already sitting in the trough are lifted out and bagged on the same visit.

Why we never put high pressure on a roof

The coloured surface of an asphalt shingle is a coat of mineral granules pressed into the asphalt. That coat is what stands between the asphalt and the sun. A pressure washer blasts it off. The roof looks clean for a while, then cracks and curls years early, and the evidence is the gritty sand that turns up in the downspouts afterwards. High-pressure water also gets driven up and under the laps, which is the one direction a shingle roof cannot handle. Cedar shakes fare no better: pressure tears the soft surface fibres and leaves the wood soaked. There is more on how each covering reacts on our asphalt shingle and cedar shake pages.

Our washing is low pressure by default. Higher pressure has a place only on tasks that call for it, such as a concrete driveway or walkway, covered under driveway and sidewalk moss. A roof is a different surface entirely.

What hand removal gives you

Working by hand is slower and less dramatic to watch, and that is the point: nothing on the roof takes more force than the moss needs, and wire brushes and metal blades stay in the truck. You keep the granules, the sealed tab edges and the dry underside of every course that a wand would have opened up.

The step-by-step of a visit, from setting ladders to covering garden beds and the clean-up, is laid out on our roof demossing page. Keeping the roof clear afterwards, including zinc strips and branch clearance, is covered under moss treatment and prevention.

Signs you can check from the ground

You do not need to climb up to know whether moss is doing damage. Stand back on the street or in the yard and look for green or brown ridges along the bottom edges of the shingles, edges that look thick or turned up, and dark streaks running down from the moss patches. Grit collecting at the bottom of a downspout means granules are washing off. Gutters overflowing in light rain usually mean moss and needles have already reached them.

Our crew has been taking moss off mid-island roofs since 2021. Every job is covered by our insurance and WCB registration, and by a guarantee: if our work is not right, we return and fix it. A quote costs nothing. Tell us roughly how big the roof is and which trees hang over it, and we will arrange a time to come and see it.