Soft washing in Sainte-Thérèse

Soft washing in Sainte-Thérèse: what matters here

In the Thérèse-De Blainville RCM, trees have grown up around houses built 25 to 50 years ago. The shade they cast encourages green algae on the siding and black streaks on the roofs.

What the service should cover

• Siding: vinyl, Canexel, fibre cement, aluminum
• Soffits and fascia
• Asphalt shingle roofs: black streaks, moss and lichen
• More delicate surfaces (brick, stone, stucco) assessed case by case
• Protecting plants and nearby surfaces during the work

Planned scope, subject to change before launch. Final details will be confirmed when the service starts.

How it is done

Soft washing is done in three stages:

1. Applying a cleaning solution at low pressure, suited to the surface.
2. Dwell time: the solution works on the organisms (algae, mould, moss, lichen) down to the root.
3. Rinsing at low pressure.

On a roof, that difference matters: a pressure washer strips the granules off asphalt shingles and can drive water under the courses. Several shingle manufacturers actually advise against it. Soft washing cleans without damage.

When and how often

Soft washing is done in the warm season, when there's no frost: from late spring to early fall. How often depends mainly on shade and humidity:

• North side or under trees: green algae comes back faster, often every 2 to 3 years.
• Roof with black streaks: they're caused by an alga (Gloeocapsa magma) that spreads over time. The longer you wait, the more they spread.
• Moss on the roof: it holds moisture against the shingles and is worth treating without delay.

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