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Inspections & Maintenance

Roof Cleaning & Moss Removal in Toronto & the GTA

Black streaks running down the shingles are the complaint we hear most — usually before a house goes on the market, or after a neighbour's pointed comment. The streaks are algae, not dirt, and they thrive on the north-facing and shaded slopes common under GTA tree cover. Moss is the more serious tenant: it holds water against the shingles through every freeze-thaw cycle and pries the tabs up as it thickens.

How the roof gets cleaned matters more than whether it does. A pressure washer will strip the streaks — along with the granules that are the shingle's entire defence against sun and weather, taking years off the roof for the sake of one clean afternoon. The right method is a soft wash: a low-pressure application of cleaning solution that kills the algae and moss, followed by gentle rinsing or letting rain and time carry the dead growth away. Thick moss gets carefully hand-removed first.

We quote roof washing honestly, which sometimes means talking you out of it. Algae streaks on shingles are cosmetic — if the roof is otherwise sound and you are not selling, you can simply live with them. Moss removal is different; that one is genuine maintenance, because moss shortens a roof's life in this climate. Either way the quote is free, and it will tell you which situation you have.

What this covers

  • Roof condition check first — a roof too old or fragile to clean gets told, not cleaned
  • Hand removal of moss build-up from shingles, valleys and shaded slopes
  • Soft wash treatment of algae streaks and remaining growth at low pressure
  • Treatment of ridge lines and shaded areas where regrowth starts first
  • Eavestrough clearing of the moss, granules and debris the cleaning dislodges
  • Protection and rinsing of plants, siding and walkways below the work area
  • Optional zinc or preventative strip installation at the ridge to slow regrowth
  • Photo record of before and after, plus anything found while up there

Just need one small job done?

Treat and remove roof moss

What affects the price

  • Roof size, pitch and height — steep or high roofs need more rigging and time
  • How thick the moss is; heavy established moss means slow hand work before any washing
  • Extent of algae staining and how many slopes are affected
  • Amount of surrounding tree cover, which drives both the problem and the cleanup
  • Landscaping and finishes below the roof line that need protecting from runoff
  • Whether preventative zinc strips are added after cleaning
  • Access around the house for ladders, hoses and rinse water

Every home is different, so we don’t publish flat prices — the quote is free and based on your actual job.

Roof Cleaning & Moss Removal near you

We take quote requests across the GTA. Local pages:

TorontoEtobicokeNorth YorkScarboroughEast YorkYorkMississaugaBramptonCaledonVaughanMarkhamRichmond HillAuroraNewmarketKingWhitchurch-StouffvilleEast GwillimburyGeorginaPickeringAjaxWhitbyOshawaClaringtonUxbridgeOakvilleBurlingtonMiltonHalton HillsHamiltonSt. CatharinesNiagara FallsGrimsbyNiagara-on-the-LakeBarrieInnisfilBradford West GwillimburyNew TecumsethKitchenerWaterlooCambridgeGuelphOrangeville

Common questions

What causes black streaks on shingles?
A hardy airborne algae called Gloeocapsa magma, which feeds on the limestone filler in modern shingles. It shows up as dark streaks on north-facing and shaded slopes because it likes moisture and hates direct sun. It is common across the GTA, it spreads from roof to roof on the wind, and it is cosmetic — the streaks look bad long before they do any measurable harm.
Is it safe to pressure wash a shingle roof?
No, and anyone offering to is telling you they do not understand shingles. High pressure blasts off the protective granules, which is the wear surface of the roof — you get a clean roof that then ages several years in one afternoon, and you may void what remains of the shingle warranty. Soft washing at low pressure with the right solution gets the same visual result without the damage.
Does moss actually damage a roof, or is it just ugly?
It damages it, and Ontario's climate makes it worse. Moss works like a wet sponge held against the shingles; every freeze-thaw cycle, that trapped moisture expands and levers the tabs and edges upward. Thick moss also blocks drainage paths and feeds rot at the eaves. Algae streaks can be ignored; established moss should come off before winter gets to work with it.
How long does a roof cleaning last before the growth comes back?
Typically several years, depending on shade and tree cover — a roof under heavy maples in Etobicoke regrows faster than an open roof in a new subdivision. Zinc strips at the ridge slow regrowth considerably, since rain washing over the metal inhibits algae and moss down the slope. Trimming back overhanging branches helps more than any product does.
When is the best time of year to clean a roof in Ontario?
Spring through early fall, on a dry day above freezing — the cleaning solutions need time to work before rain, and nobody should be on a frosty roof. If moss is heavy, aim to have it removed before late fall so it does not spend another winter holding water against the shingles. Booking before the house goes on the market is the other common deadline we work to.

Ready to sort out your roof cleaning & moss removal?

Tell us what your home needs — a small fix or a full project — and get a free quote.

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