How are zinc (or copper) strips installed to provide mildew protection? How wide are the strips? Do you lay a strip under the ridge shingles with a bit of the metal exposed? How are they nailed?

 

bump..........................

 

I would love to hear an answer to this question....

 

I'm surprised there's no answer. I really thought this question would be of general interest, plus it's never been addressed before on this forum. I know - I searched. Plus I would really like to know the answer, as I plan on installing light-colored shingles in a climate that's damp in a neighborhood with large shade trees where most of the houses suffer from mildew on the roof.

 

I agree, it sounds like a fairly common issue. I've also heard in addition to zinc you can install copper. Even wire, I think. I would imagine you just use a long staple to hold the wire towards the top of the roof, just below the shadow line of a course of shingles.

From thisoldhouse.com: (http://www.thisoldhouse.com/toh/tvprograms/asktoh/qaarticle/0,16588,401167,00.html)

To keep the algae from coming back, insert 6-inch-wide strips of zinc or copper under the row of shingling closest to the roof peak, leaving an inch or two of the lower edge exposed to the weather. That way whenever it rains, some of the metal molecules will wash down the roof and kill any algae trying to regain a foothold on your shingles.

You can probably see this same principle working on roofs in your neighborhood. Look for chimneys with copper flashing; the areas directly below the flashing will be free of any algae stains.

The strips also work on roofs suffering from moss buildup. Just scrub it off first with a brush, then bleach as above.