On Dec 5, 8:10�am, Roof Time Cincinnati wrote:
At Roof Time LLC, we have heard people explain those black streaks on
roofs as being caused by everything from chimney smoke settling, or
acorns cracking on the surface, to tree sap or shingle weathering due
to granule loss. One roofer even told a homeowner that lived by the
airport, that jet fuel dropping from the sky was the culprit!

The fact is that in most cases, the stains and streaks are a form of
algae. Black streaking is actually caused by a specific type of living
algae known as Gloeocapsa Magma.

The staining is a relatively new occurrence, in northern climates but
has been around for years down south.

Cutting back on tree canopy, or forgoing the use of a fireplace will
not correct the problem.

The spores are air-borne and as such, are driven through-out the
neighborhood by the wind, settling when and where they will. To grow
into a visible colony, they require the correct amount of three key
elements.

� � � � �Humidity

� � � � �Limestone (a key shingle ingredient)

� � � � �Sunlight

So you might ask, if this is true, how come my neighbor has nothing
and my roof looks like swamp thing walked all over it?! The sunlight
is probably the culprit. Too much sun, and the colony burns up, too
little and it never gets started! That's why even on the same home,
only certain roof faces are affected, and not others.

To properly element roof staining, you should always consider that
COPPER stripping be applied after the cleaning phase to help prevent a
new infestation. We would not reccomend the use of ZINC because of
it's harmful potential as it relates to cisterns, animals drinking
from downspout puddles, and the fact that it can act as a corrosive
agent when in contact with aluminum, (your gutters)! Metal oxidation
also helps as a colony preventative. Look directly under the chimney,
soil pipe flanges, and other metal roof protrusions, and you will
likely find that the roof is free of discoloration.

Roof moss is different from algae. �MOSS is more dangerous because it
will grow underneath the roof shingle and act like a sponge soaking up
water after a good rain. �Eventually the moss will cause roof leaks if
not treated. �Also, moss, once attached to a shingled roof, feeds on
the dead organic matter used in the manufacturing process of the
shingle. �As the fungus breaks down the asphalt shingle, the ceramic
granules protecting the surface of the shingle are loosened and begin
to fall off. �This causes the roof to deteriorate prematurely and
diminishes the roof's abilities to reflect heat rays.

Roof moss ccumulates on the North side of the home or where shade is
most prevalent.

Only a professional roofer should attempt to remove roof moss, as it
almost always requires some shingles to also be replaced.

The initial removal of roof algae and moss is always more difficult
then the prevention of roof algae or moss once the roof is cleaned. �A
standard practice should be to clean your roof and then apply a
preventative such as zinc bars, Z-stop, or copper strips, (use the
copper!) to keep the stains from returning.

With the advent of new products designed to fight discoloration, and
companies accepting work to clean shingles, roof cleaning and
prevention has never been easier. But a word of caution; there is a
right and a wrong way to fight the problem. Roof Time has responded to
many homeowners over the past ten years that have caused their roof to
begin to leak, by doing all the wrong things!

NEVER:

� � � � �Force water up and under the shingle seal

� � � � �Scrub the roof with a hard bristle brush

� � � � �Dump pure bleach over the shingles

Many people spend countless hours and money cleaning their respective
homes every year only to ignore one of the most visible and important
aspects of the home; the roof. �Adding a roof algae/moss prevention
program to your annual spring cleaning chores will result in a
beautiful home that looks fresh and clean!

When it becomes time to replace your old roof, having your roofer bid
shingles specifically manufactured to fight discoloration, such as
those made by CertainTeed, ELK-GAF, �and some others, will help to
eliminate the problem from coming back!

Good Luck

some good solid info, my home has the streaks for the very first time
but only in the back of the house, which has tree shade from a 200
year old tree.

its widespread here but had never seen it before this year perhaps its
a global warming effect.

it snowed here perhaps that will kill it off?