Different problems, different solutions
Soft wash roof cleaning and roof rejuvenation are both growing in popularity across Ontario — and they're often confused with each other, or assumed to be the same thing. They're not. They address completely different problems, and understanding which one your roof needs could be the difference between money well spent and money wasted.
The short version: soft washing deals with what's on top of your shingles. Rejuvenation deals with what's happening inside them. One cleans. The other restores.
If your roof has visible algae, moss, or black streaking, soft wash cleaning addresses that. If your shingles are 7–20 years old and showing age-related brittleness or granule loss, rejuvenation addresses that. Many roofs benefit from both — clean first, rejuvenate second.
What is soft wash roof cleaning?
Soft washing is a low-pressure cleaning method that uses a biodegradable chemical solution — typically sodium hypochlorite mixed with surfactants — to kill and remove biological growth from your roof. This includes algae, lichen, moss, mould, and the black streaking caused by Gloeocapsa magma, a type of cyanobacteria that feeds on the limestone filler in asphalt shingles.
Unlike pressure washing (which can damage shingles by blasting away granules), soft washing applies the chemical solution at low pressure and lets it do the work. It's safe for asphalt shingles when done correctly by a trained professional.
What soft washing treats:
- Black streaks or staining from algae growth
- Green moss patches, especially on north-facing slopes
- Lichen — the grey-green crusty growth that bonds to shingles
- General grime, dirt, and surface discolouration
What soft washing does not do:
- Restore the oils or flexibility of aged shingles
- Extend the structural life of your roof
- Prevent future biological growth permanently
- Fix granule loss, cracking, or brittleness
What is roof rejuvenation?
Roof rejuvenation is a bio-oil treatment applied by a certified contractor to the entire surface of your asphalt shingles. As shingles age, the petroleum-based oils that keep them flexible and waterproof gradually evaporate — accelerated by Ontario's UV exposure and freeze-thaw cycles. Once those oils are gone, shingles become brittle, crack more easily, and begin to fail.
Rejuvenation replenishes those oils at a molecular level. The treatment penetrates the shingle surface and restores the properties that keep it waterproof and weather-resistant. It doesn't clean the surface — it restores what's underneath it.
What rejuvenation treats:
- Brittle, dried-out asphalt shingles aged 7–20 years
- Age-related granule loss and surface degradation
- Reduced flexibility that makes shingles prone to cracking
- General loss of waterproofing and UV resistance
Removes biological growth from the surface. Makes your roof look clean. Does not restore shingle integrity.
Restores oils inside the shingle. Extends roof life 5–15 years. Does not clean biological growth.
Clean first, then rejuvenate. The ideal sequence for roofs that are both dirty and showing age-related wear.
Do you need both?
Possibly — and there's actually a logical sequence to doing both that makes each treatment more effective.
If your roof has significant biological growth (algae, moss, or lichen), it's worth having it soft washed before applying a rejuvenation treatment. Here's why: the rejuvenation solution needs to penetrate the shingle surface to work. A thick layer of algae or lichen can act as a barrier, reducing how well the treatment absorbs. Cleaning first gives the rejuvenation the best possible chance of full penetration.
If your roof is relatively clean but aged and brittle, you can skip straight to rejuvenation.
Recommended sequence if doing both:
- Soft wash the roof to remove all biological growth
- Allow the roof to dry fully — typically a few days of dry weather
- Apply the rejuvenation treatment to the clean, dry shingles
Ontario's climate — particularly the humid summers and shaded sections of roofing — creates ideal conditions for algae and moss growth. North-facing slopes and roofs near mature trees are especially prone. If you notice dark streaking or green patches, that's biological growth, not just dirt — and it spreads if left untreated.
What about roof cleaning services that claim to do both?
Some contractors offer combined cleaning and treatment packages. This can be a good option, but make sure you understand exactly what's in the treatment component. A chemical clean followed by a sealant coating is not the same as a proper rejuvenation. Ask specifically whether the treatment contains bio-oils that penetrate the shingle, or whether it's a surface coating only.
Genuine rejuvenation products — like those independently tested and certified by roofing research bodies — will have documentation to back up their claims. A reputable contractor should be able to tell you exactly what product they're using and what it does.
Cost comparison
- Soft wash roof cleaning — typically $300–$800 for an average Ontario home, depending on roof size and growth severity
- Roof rejuvenation — typically $500–$2,000 for an average home
- Both together — some contractors offer a combined discount; expect $700–$2,500 total depending on scope
Both are a fraction of the cost of roof replacement, which runs $12,000–$22,000 for a typical Ontario home.
The bottom line
Soft wash cleaning and roof rejuvenation are complementary services that address different problems. Cleaning removes what's on the surface. Rejuvenation restores what's inside the shingle. If your roof needs both, the smart approach is to clean first, then rejuvenate — ideally with a contractor who understands both treatments and can assess which your roof actually needs.
Not sure where to start? A free roof assessment from a local specialist will tell you the condition of your shingles, whether biological growth is a factor, and which services make sense for your specific situation.