Replies

1. 
   Oak River Mike | Nov 17, 2009 05:44am | #1

   I used a zinc strip up towards the top of the roof on mine and it seems to help.  Rain water washes the zinc down onto the algae and kills it.

   I do still get it in other areas where I haven't put a strip.  I just clean those each year or so.

2. 
   sawdust58 | Nov 17, 2009 06:55am | #2

   when I see moss starting on my roof i get after it with Roundup, seems to do the trick

3. 
   DanH | Nov 17, 2009 07:04am | #3

   Note that there are two different things -- moss and algae. Moss generally only shows up on roofs that are beginning to break down, giving the moss a literal root-hold. The algae can show up on brand-spanking new roofs. (Why the heck aren't they "rooves"??)

   A chlorine bleach solution sprayed on either will generally kill it (though RoundUp or something similar is probably better for moss). Zinc or copper strips applied along the ridge are effective in preventing algae and at least somewhat inhibiting moss.

   And, of course, you can buy shingles (at least in some colors) that contain copper or zinc and are naturally resistant to algae growth.

   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
4. 
   PatchogPhil | Nov 17, 2009 07:25am | #4

   There is some product in a garden hose end-sprayer bottle that you spray onto the roof and siding to kill the mildew. I cannot recall the name.

   Some people use Tide laundry detergent.

   Do a Google search for product names. Or go to a Bog Box store.

    

   Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
   

1. 
   Nuke | Nov 18, 2009 04:17pm | #5

   Most of the homes in phase 1 of my tract community have a fungus problem on the roof. Mine is no exception. I, too, am wondering how I can treat this issue if the roof itself isn't replaced beforehand.

   I am not getting on my roof. :)

1. 
   DanH | Nov 18, 2009 04:28pm | #6

   Can't do much without someone getting on the roof.
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

5. 
   renosteinke | Nov 19, 2009 02:08am | #7

   In St. Louis, my Dad has the same issue. His solution is to spray his roof with bleach every Autumn. He uses a ladder and one of those garden pump-sprayers.

   The result? His roof is clean, while the neighbors have extensive staining.

6. 
   WayneL5 | Nov 19, 2009 03:41am | #8

   If there are trees overhanging the roof the additional shade and the reduced air circulation can increase growth on the roof.  If so, trim back branches.

1. 
   Matt | Nov 19, 2009 03:25pm | #9

   I too live in an area where roof staining is a big problem.  To the point where most all builders install dark colored roofs.  Although it is counter intuitive, the overhanging tree thing doesn't seem to hold.  Roofs in full sun have the problem just like others do. 

   Only solution I know of is to be sure and install AR (algae resistant) shingles.  Knowing this doesn't help after the fact.

   Our last house had a medium brown roof with no staining after 10 years (AR shingles).  Others in the neighborhood looked rather dismal with all the black staining.

1. 
   DanH | Nov 19, 2009 03:47pm | #10

   One interesting thing to do is to look on stained roofs just downhill of galvanized vent jacks, antenna masts, etc. You'll always see a clear area where the zinc in the galvanized metal has prevented algae growth. It's a good illustration of the effectiveness of zinc/copper in preventing this problem.
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

1. 
   Matt | Nov 19, 2009 11:14pm | #11

   I wonder if the AR shingles contain zink?

1. 
   DanH | Nov 20, 2009 03:20am | #14

   Zinc or copper.
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

2. 
   Nuke | Nov 20, 2009 12:29am | #13

   This doesn't apply in my case, either. While the biggest stain is in a vacainty of a galvanized dryer vent, the stain's streak starts higher. Also, I have streaking from this fungus in the morning shadow areas of my dormers.

1. 
   DanH | Nov 20, 2009 03:23am | #15

   If you've got staining downhill from galvanized then it's probably not algae. You can get staining from tannins in leaves and nuts, of course. And you can get moss growing, which is only modestly inhibited by the zinc.
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

2. 
   Nuke | Nov 20, 2009 12:27am | #12

   Overhanging tree? Maybe, but not in my neighborhood's case. Most of the phase-1 houses have this problem, and almost all of the development was clear-cut. This image is about three years old, I think, maybe 4. Ain't no trees on my street to afford the fungus easy reach to the front of the house. Also, in that photo the morning sun would be coming from the picture's upper-left corner, setting in the lower-right. And the predominant (90%) wind/rain for the lower-right.

1. 
   excaliber32 | Nov 20, 2009 04:17am | #16

   So now I know where you live and if you tick me off, I can find you.................brilliant!