What those black streaks are
The dark streaks running down a lot of Denver roofs are a type of algae that feeds on the filler in asphalt shingles. Moss and lichen show up too, mostly on the north side and under trees. All of it holds moisture against the shingles and shortens the life of the roof.
Why we never pressure wash a roof
High pressure knocks granules off shingles, and the granules are what protect the roof from the sun. Many shingle makers say not to pressure wash at all. Tile and metal don't do well with it either.
A soft wash kills the growth at the root. Streaks lighten the same day and keep fading for a couple of weeks as rain rinses off what's left. Thick moss gets treated and then brushed off by hand where it's safe to do that.
How we work on your roof
Anyone on the roof is in a harness and tied off. On lower pitches we do as much as we can from the ladder and the ground. We soak the plants under the drip line, flush the gutters and downspouts so runoff doesn't sit in them, and cover AC units and patio furniture under the roof edge.
Roofs we clean
- Asphalt shingle
- Concrete and clay tile. We only walk tile where it's safe and often work it from a ladder.
- Metal
- Cedar shake, with a weaker, wood-safe mix
What we don't do
We don't do roof repairs. If we see lifted shingles, cracked tiles, or bad flashing while we're up there, we take photos and send them to you so a roofer can take a look.
Roof cleaning questions
Will this void my roof warranty?
Pressure washing can cause warranty problems. A low-pressure soft wash is the method most shingle makers point to for algae.
How long until the streaks are gone?
Most of it is gone the same day. The rest fades over one to three weeks.
More in the FAQ, or get in touch.
