Why this usually happens
Greying: UV breaks down the surface fibres of untreated or worn wood.
Green and slippery: algae and mildew grow in damp, shaded sections.
Composite decks get the same green growth even though they do not grey.
Why you should not ignore it
A slippery deck is a fall risk, especially around pools and steps. On wood, trapped moisture and growth accelerate rot and shorten the deck's life. Cleaning before it's badly degraded saves the cost of replacing boards.
Decks across Durham Region take a beating from snow, rain, spring pollen, summer sun, shaded yards, pool moisture, and fall leaves. Wood can grey from UV exposure while algae or mildew builds up in shaded areas, steps, railings, and boards that stay damp. Composite decking avoids some wood-weathering issues, but it can still become green and slick when organic growth sits on the surface.
What to do next
- Avoid high pressure on wood — it gouges and splinters the soft grain.
- The right approach is a controlled, low-pressure cleaning with a treatment that removes greying, algae, and mildew without tearing up the wood — leaving it ready to enjoy or to stain and seal.
A safe exterior cleaning approach
Our deck and fence cleaning safely restores wood and composite decks — removing grey, green, and grime and bringing back the natural surface. Serving Durham Region.
Related DSS services and local pages
Frequently asked questions
Can you clean composite decks too?
Yes — composite gets algae growth and cleans up well with the right method.
Will cleaning damage the wood?
Not with our low-pressure method; high pressure is what damages decks.
Should I clean before staining?
Yes — a proper clean is essential prep for stain or sealer to adhere.