On Sunday, June 22, 2003 at 10:39:10 PM UTC-4, jim wrote:
NO NO NO NO NO! thebleach will permanetely damage the shingles!
Leave it be or buy a product specific for the mold.....
roofers can add some metal stips toprevent it from re growing.
its a effect of global warming
On Friday, May 22, 2015 at 9:29:43 AM UTC-4, bob haller wrote:
You're reviving a 12 year old thread.
GAF, one of the largest manufacturers of shingles, disagrees:
"Mold. Discolored streaks on a roof indicate there is mold, algae, or fungu
s, which can eat away at the roofing material and, ultimately, cause leaks.
A treatment of chlorine bleach or copper sulfate solution applied with a g
arden sprayer can kill the mold. GAF manufactures algae-resistant shingles
that have a specially formulated granule that inhibits algae growth, in add
ition to shingles with StainGuard® Protection. Finally, do not power wash
shingles! It can dislodge granules and cause premature shingle failure."
So does the assoc of roofing manufacturers:
"The most effective method of cleaning algae and moss from a roof is with a
50:50 mix of laundry strength liquid chlorine bleach and water. Apply with
a sprayer and allow the solution to dwell on the roof surface for 15 to 20
minutes, and then rinse thoroughly with low pressure water. "
That's what the sellers of those products want you to believe.
Those would be zinc strips. They work, but are marginally
effective. They protect an area about 4 ft below where they
I suppose it's an immediate threat to our national security, too.
While the thread is very old, the main reason for the growth is the shingles
used to have copper and maybe zinc in them. Over the years they cut way
back or eliminated the elements that stopped the growth. I just had a roof
put on and they have started putting more growth preventive chemicals back
into the shingles and have a long warrenty about that growth.
Many roofers use bleach, but others have stopped because it can discolor
shingles and kill plants below the eaves.
Some who have quit bleach swear by washing soda. Others say borax or
trisodium phosphate. When I happened to be on my roof, I sprinkled
baking soda on the moss, from a can similar to a Parmesan cheese jar. In
a few days, the moss was brown.
For a bigger job, I'd use borax in a garden sprayer. The general-purpose
solution is 2 tablespoons per quart of water. It dissolves best when
heated to about 140 degrees (steaming) on the stove. A bit of detergent
could help it soak in.
It would be nice if sprayer manufacturers would publish vertical
capability and gallons per minute. My one-gallon sprayer with a hose and
wand will spray 10 feet up. My one-hand sprayer will spray 15 feet up.
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