Moss on asphalt shingle roof

Discussion in 'Roofing and Siding' started by DFBonnett, Aug 2, 2014.

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  1. Aug 2, 2014 #1

    DFBonnett

    DFBonnett

    DFBonnett

    Retired decorating contractor

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    Because of heavy shade there is moss on an 8 year old asphalt shingle roof. Removing the trees is not an option at this time, nor is getting on the roof to remove the moss manually. I have sprayed with a strong bleach solution and that worked to a degree but my concern is damaging the shingles. Any advice about a preferable product or method would be most appreciated.
     
  2. Aug 2, 2014 #2

    oldognewtrick

    oldognewtrick

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    The less activity you have on the roof the better off for the life cycle of your asphalt shingles.

    That being said, ABC Roofing Supply sells a product called "Shingle Shield" that I've used with varying degrees of success. It's is a concentrate that you mix with water and spray with a garden sprayer and rinse with a water hose. Avoid any pressure washer use on the roof, cause it will dislodge your shingle granules and shorten the lifespan of the roof. Repeated applications may be required.

    There are Zinc strips that can be installed along the ridge and hips that help to some extent with keeping roofs clean to some extent. If you've ever noticed clean areas below a chimney, it's the wash off from the copper that creates an environment that is not conducive to mold, algae and organic growth.

    Next time you have a roof installed, ask that an algae resistant shingle is installed. There are zinc granules incorporated in with the stone granules to help keep organic growth down. If you have a AR shingle, call the MFG and make a claim. They may pay to have a professional clean the roof.
     
  3. Aug 2, 2014 #3

    Wuzzat?

    Wuzzat?

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    If all else fails, for a small area I guess you could heat the roof from underneath. Wood insulates somewhat so perhaps small holes in the sheathing may help with heating the shingles with violating structural rules.

    But, how long will it take to know if this works? How fast can you kill that moss with a hair dryer?
     
  4. Aug 2, 2014 #4

    oldognewtrick

    oldognewtrick

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    Are you serious?
     
  5. Aug 2, 2014 #5

    Chris

    Chris

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    Last time I drilled holes in my roof it leaked.
     
  6. Aug 2, 2014 #6

    Wuzzat?

    Wuzzat?

    Wuzzat?

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    Just the plywood underlayment. Not through holes. :hide:

    The trick is to make the shingles hot enough to kill the moss but
    not hot enough to unduly shorten the life of the shingles.

    I have to be more literal.

    Maybe reducing attic ventilation will help, over time.

    BTW, darker shingles should work better at preventing moss because they will absorb more light and so be hotter, on average.
     
    Last edited: Aug 2, 2014
  7. Aug 2, 2014 #7

    oldognewtrick

    oldognewtrick

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    I disagree with everything you've posted here. If you don't have proof that taking these actions work, please don't post them because it will void any warranties available from the shingle MFG's. And you will have a unknowing homeowner doing damage to their home that will cost lots of $$$ to fix.
     
    CallMeVilla and DFBonnett like this.
  8. Aug 2, 2014 #8

    Wuzzat?

    Wuzzat?

    Wuzzat?

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    Feel free to delete my posts. Whatever I post that this forum can use, use it. Otherwise, out with it.

    Proving what is posted on any forum is a pretty heavy burden, though.

    http://en.wikipedia.org/wiki/Burden_of_proof

    I'd hope that what I post is "more likely than not" to work (the 51% rule). The "beyond a reasonable doubt" (>95%) level I cannot guarantee, sometimes even with electrical matters.
     
    Last edited: Aug 2, 2014
  9. Aug 3, 2014 #9

    CallMeVilla

    CallMeVilla

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    OldDog ... Interested in the zinc strips ... Can they be applied in long runs above and spaced within the area with moss? A one time remedial repair to the roof could be the answer here. I like the idea ...

    mossy-roof.jpg
     
  10. Aug 3, 2014 #10

    oldognewtrick

    oldognewtrick

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    I think thats just a tad more than the zinc strips can handle. Yes, they are applied the whole run of the ridge, just below the shingle cap. Then run at a diagonal down the hips (if there are hip) so you have wash off on the entire roof.

    We did a huge slate roof that had previous staining. We fabricate a copper strip that was exposed just below the ridge capping so we got wash off of the copper all along the ridge and hips. From the ground you could barely see it.
     
    inspectorD likes this.
  11. Aug 31, 2014 #11

    BigDawg72

    BigDawg72

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    Bleach will dry out the shingles and shorten the life dramatically. A roof works best when water flows downward and if any debris is on your roof that re-directs water sideways (leaves, pine needles, limbs, etc.) then you risk it leaking, not always enough to damage your ceiling but enough to damage the deck. Most rotten wood I have replaced over the last 30 years has something to do with a tree or tree debris. Trim the trees as far back away as you can and keep debris out of your gutters, valleys, and roof in general or it will be costly down the road.
     

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