Roof Cleaning & Moss Removal in the Lower Mainland

Why roofs here grow so much moss

Moss needs three things: moisture, shade and something to hold onto. The Lower Mainland supplies all three for the better part of the year. Our winters are wet but rarely cold enough to kill growth off, mature conifers shade whole roof slopes for months, and the granular surface of an asphalt shingle is an ideal anchor.

North-facing slopes and anything under overhanging branches are almost always worst — those sections can stay damp for weeks at a time between October and April. It's why a roof can look fine on one side of the ridge and be carpeted on the other.

What moss actually does to a roof

It's easy to write moss off as cosmetic. It isn't:

• It holds water against the shingle instead of letting it run off, keeping the surface permanently damp.
• It grows underneath and lifts shingle edges, creating gaps for wind uplift and wind-driven rain to get in.
• Its root structures pull granules off the shingle surface — and those granules are the shingle's UV protection.
• It expands when it freezes, so a cold snap turns established moss into hundreds of small wedges working under the shingles.
• It blocks water flow, causing pooling behind moss dams and overflow into the gutters and fascia.
• It can affect your warranty. Most asphalt shingle warranties are conditional on reasonable maintenance, and unchecked moss growth is a common reason a claim gets pushed back.

Why we never pressure wash a roof

This matters enough to say plainly: pressure washing an asphalt shingle roof will damage it, and anyone offering to do it should be turned down.

The coloured granules bonded to a shingle's surface aren't decoration. They're the UV shield and a significant part of the fire rating, and once they're gone the asphalt underneath begins to break down. High pressure strips them in sheets. A pressure-washed roof looks dramatically clean the same afternoon and can have a decade taken off its service life — with the granules sitting in the gutters as evidence. The Asphalt Roofing Manufacturers Association advises against it, and so does essentially every shingle manufacturer's own care guidance.

The correct method is a low-pressure application of a roof-safe treatment that kills the moss and leaves the shingle alone.

How we do it

1. Inspect before anything else

   We assess from the ground and from the roof where it's safe to do so — overall condition, lifted or damaged shingles, flashing, and how far the growth has actually progressed.

2. Clear the bulk by hand

   Thick moss mats are removed gently by hand and with soft tools, working down-slope so nothing is forced under the shingle edges.

3. Protect below

   Landscaping is soaked and covered, and downspouts are managed so runoff goes where we want it rather than into your beds.

4. Apply a roof-safe treatment

   A low-pressure application across the affected slopes, worked into the areas where growth is heaviest.

5. Let the weather finish the job

   The moss dies off and then weathers away gradually over the following weeks. This is normal and expected — see below.

6. Clear the gutters

   Dislodged debris is cleared from the gutters and downspouts are flushed and flow-tested so nothing is left to block up.

What to expect afterwards — and what not to

Worth being upfront about, because it's the most common surprise: after a soft wash, the moss dies but it does not vanish that afternoon. Dead moss loses its grip and weathers off over the following weeks and months as rain and wind do the rest. Depending on how thick it was, a roof can take a full season to look completely clear.

The alternative — scraping or blasting everything off in one visit for an instant result — is exactly what damages shingles. A contractor who promises a spotless roof by the end of the day is telling you they're going to be aggressive with it. We'd rather explain the timeline honestly than hand you a clean-looking roof that's been shortened by years.

Roof types we work on

• Asphalt shingle — by far the most common here, and the most vulnerable to both moss and bad cleaning.
• Cedar shake — needs particular care; cedar is soft, and the wrong chemistry or pressure ruins it quickly.
• Concrete and clay tile — durable underfoot but brittle, so access has to be planned rather than improvised.
• Metal — generally straightforward, with attention paid to coatings and fasteners.

Keeping it from coming straight back

Zinc or copper strips installed along the ridge are the most effective preventative measure available. Every time it rains, trace amounts of metal wash down the slope and make the surface inhospitable to moss and algae. It isn't a permanent fix and it works best on the slopes directly below the strip, but on a roof that's just been cleaned it meaningfully extends the interval before you need us again.

Trimming back overhanging branches helps at least as much — more light and airflow on a roof slope does more than any product. And keeping the gutters clear stops the damp, debris-packed edge where regrowth almost always starts.

Best time of year

Spring and early autumn are ideal. We want a stretch without heavy rain so the treatment isn't washed off before it works, and temperatures above freezing. Mid-summer is fine too. The one period we'd generally steer you away from is deep winter, when persistent rain and cold limit how effective any treatment can be.

What affects the price

• Roof area and pitch. Steeper roofs need more equipment and take longer to work safely.
• Number of storeys and access. A three-storey home on a sloped lot is a different job from a rancher.
• How established the moss is. Light algae staining is quick; thick mats need hand-clearing first.
• Roof material. Cedar and tile need more care and time than asphalt shingle.
• Whether gutters are included. Most people bundle the two, since roof debris ends up in them anyway.

Frequently asked questions