>>If it bothers you then there is a product you can get called moss off or
some such that also works on lichen. At Home Depot it is too damned
expensive, but our local landscape shop has a product<<

Why support the petro-chemical corporations with your dollars? On sloped 
roofs we have had good success keeping the mold, lichen and moss from 
growing by flashing the ridge with copper or lead. Even running a single 
line of bare copper wire along just under the edge of the upper coarse 
of shingles can work. On one project we reused the old worn out copper 
screening from the windows, tacking a 3" wide strips along the ridge.

On a flat roof you might just put out a few scraps of copper or copper 
screening.

I have seen clear cut evidence that lichen and moss do consume and 
deteriorate the structure of asphalt shingles. It is well known that a 
thick moss does damage wood shingles, but that when it is wet and rainy 
the moss expands and can keep the shingles from leaking.

The strategy of homeowner insurance companies is to limit their coverage 
and create excuses to drop policies on older houses. This is how the 
industry scrapes money out of poor homeowners to pay out on the big 
claims like the one on the World Trade Center. The insurance payout on 
that tragic fiasco shook the foundation of the entire insurance industry 
world-wide, which figures it will take 40 years of bilking howmowners to 
get their money back. I can't wait to see what they do when the 
crackerbox cardboard and plastic MacMansions start falling apart in 
about 10 years.

Then we will be growing moss on our cardboard roofs and harvesting it to 
feed our kids. (those of us lucky enough to have a piece of cardboard to 
live under.)

John (eating moss for breakfast, just to get in practice) Leeke

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