A Seattle roof gathers woe moss

A mossy roof in Seattle

A mossy roof in Seattle

As I review the characteristics that help define Seattle, several come to mind. They include beautiful vistas, liberal politics, omnipresent coffee shacks and, increasingly, LGBT relationships (led by the voters’ legalization of gay marriage and a openly gay new mayor, Ed Murray, who talks up his husband at every opportunity).

Here’s another: roof moss.

Various climatological factors make the tops of many Seattle houses look like petri dishes for clumps of green growths. The appearance is not exactly that of the quaint thatched roofs found in parts of the U.K. To me, a better label would be residential acne.

No less an authority than the Washington State University agricultural extension office in King County (where Seattle is located) has issued a published warning:

The unsightly look of moss on roofs is not the only reason that control of this moss is important. Moss will often grow so vigorously that it causes the singles or shakes to become loosened and raised. Under very wet conditions, water can back up under these raised areas and cause interior leaks and water damage. Often accompanying the moss will be a green coating of algae on those areas that the moss has not yet colonized. Algae becomes very slipper and treacherous and have been implicated in more than one roof-related disaster.

Seattle’s climate–abundant rain and humidity, plus moderate temperatures and minimal sun–is conducive to moss growth, but the city hardly is alone. However, in Seattle roof moss removal is something of a big industry unlike anything I have witnessed elsewhere. I hear competing commercials on the radio for the service, just like the spots aired in this sunshine-deficient climate by sellers of Vitamin D. From time to time I even have been cold-called at the New To Seattle world headquarters by moss removers who–lucky me–just happen to be working in my neighborhood.

I recently hired someone to climb up on my roof and whack all the moss (cleaning out gutters and pruning touching tree branches at the same time) while laying down something to keep the green stuff from reappearing for awhile. I paid my moss man–I don’t know what else to call him–about $400. That seems to be the going rate in Seattle for such a task, which is close to a day-long job involving tools, a high-pressure hose and application of the final treatment.

I have heard a fair amount of folk lore in Seattle about roof moss. Some of it even appears to be true. Moss tends to grow better on a roof’s north side, which gets less sun and thus retains longer the moisture that moss craves.

But a lot of the talk seems doubtful to me. For example, I have been told more than once that roof damage comes because mosses are acid-seeking plants that literally eat into shingles, which are acidic, creating holes. From what I can tell, the damage comes not from an appetite but because the sheer growth of moss over time can dislodge those shingles, creating openings for some of Seattle’s 37 inches of annual rain.

In this city of professed environmentalism, there does seem to be a split of opinion on what to put on a roof to retard future moss growth. The garden stores sell all kinds of herbicides, but the storm run-off could cause pollution to bodies of water and damage to vegetation below. Believe it or not, the classic fix is to nail zinc strips near the peak of the roof. For some reason, zinc kills moss and the gradual dispersion as the strips weather does the trick. But this is very expensive.

My moss man took a lighter approach. He laid down a dusting of simple laundry detergent, which, since it is used to clean the clothing we wear, isn’t that toxic. He said the more it rains, the better the anti-moss effect.

Roof moss removers–in Seattle and anywhere else–haven’t yet been celebrated in folklore, mythology or culture like another category of human rooftop workers, chimney sweeps. They originally were perceived in the U.K. and the U.S. as child labor exploiters–only kids were small enough to wiggle into dangerously narrow flues. But eventually, chimney sweeps got better press–thanks partly to the development of cleaning tools eliminating the need for children–to the point where their image today is that of agile, good-natured folks who bring good luck.

That industry might also thank Dick Van Dyke’s turn as an amicable chimney sweep in the celebrated 1964 movie, Mary Poppins.  The famous tune he sung, “Chim Chim Cher-ee,” actually won the Oscar for best original song.

Thus, I perceive a promising promotional opportunity in Seattle. Maybe a reality TV show. I could see Green’s Anatomy. Or maybe Mossless in Seattle.

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