Alge Stains on Roof shingles

[radioman]

prevention is the best option. scrubbing asphalt roof is a bad idea. You don't want to remove any of the rocks embedded in the tar felt.

I'd spray bleach if the roof is white otherwise use a commercail product. I would add a exposed strip of copper or zinc just under the top row of shingles on roof and let the rain do its work.

 

[scott_vt]

Good Afternoon Greg,
I was just looking up at my roof on the rear side, north side of the house, and thinking what my best options were ! So glad you brought it up !

The house was built in 83 so we are closing in on 30 years, so Im not sure how much more I can get in longevity out of these shingles anyway...

What has saved the roof in my opinion to date, has been the shade it has recieved...

The shingles are still not curled or cracked after all those years, so I guess that says something about sheilding against direct sunlight !

Before reading your thread I was thinking along the lines of a 1/4 Clorox to 3/4 water solution and one of the old indian tanks we use over the FD for a long distance spray... I will be keeping my eyes open for other good suggestions like the galvanized strip the others suggested !

Geee after looking at that photo I just took closer, there isnt much in the way of algae anywere near that copper flashing on the chimney...

 

[beersngars]

Thanks for all the replys. After a bit more reading, I have decided to try a concoction of 1 gallon of 6% sodium hypochlorite (Clorox), 4 gallons of water and 2 cups of trisodium phosphate (TSP). I will spray in on and let it sit for about 15 minutes and then hose it off.

As far as the preventitive measures of copper and zinc, a lot of the success of depends on your roof design, pitch and the shade/sun factor from my reading. I will let you know how my plan works out. It may be a week or two before I can get to it.

 

[buckeyefarmer]

I recommend "Wet and Forget". Used it this summer and it works great. Just spray it on your roof and you're done. Requires no scrubbing or rinsing. You can get 1 gallon at amazon.com for $27 plus $10 shipping. 1 gallon makes 6 gallons of ready to use product, which will cover approximately 2000 square feet.

I got it at costco. haven't tried it yet.