Roof Stains in the Pacific Northwest

Green roof stains found in Oregon and Washington.

During the fall a trip to Portland, Oregon and Seattle, Washington revealed 30% of roofs stained by green algae, mold and moss.   These roof streaks confirmed that algae roof stains can be found from the Florida Keys to the other corner of the country, Washington’s Olympic Peninsula.

In this region the pattern leans more toward moss, and green algae driven by the high degree of moisture and low amount of sunny days.

We have covered the tell tale signs of roof algae stains in previous post, so I won’t go into detail here.

Instead just a few words about roof cleaning when moss is present.

Moss and Roof Cleaning

Roof Stains can range from a thin film of green or black algae, to a dense carpet of green moss. Cleaning roof stains requires use of a quality shingle roof cleaner in all cases. When it comes to Roof Cleaning, moss roof stains sometimes require brushing to work the cleaner into moss (which can be as dense as carpeting).

Roof Cleaning Brush Technique

For roof cleaning green moss from roof shingles, start with a normal application of the roof cleaner, followed by a high volume rinse. In some cases, a single application of roof cleaner will do the job.

Thick moss may not removed by a single pass of roof cleaning; in this case find a Vehicle Wash Brush, a soft bristle brush that is used to clean your car (ie. it won’t scratch surfaces). Apply a second pass of roof cleaner, and before rinsing, run the brush across the moss to help work the roof cleaner into the moss. Then let the roof cleaner soak the remaining time, and rinse with a little more pressure!

Why the Wash Brush and Roof Cleaner Combination works

Because roof moss is so dense, any roof cleaner can have difficulty penetrating the moss.

A roof cleaning product can not clean moss that it can’t reach!

So the wash brush helps to open spaces in the moss, allowing the roof cleaner to soak into the lower levels of the roof moss. On the most dense of moss covered roofs, 2 or 3 applications may be needed to penetrate back down to find the shingle surface.