Corrosive roofing shingles damaging painted siding?

santillaMay 21, 2010

Has anyone seen this before? The paint on my siding is being eaten away, and it appears to only happen in places where rain can either bounce off the shingled roof or run down onto the paint from a roof gully. This just started happening about a year ago in a couple tiny spots and is suddenly looking really bad.

The roofing is architectural shingles, but I don't know what brand. The siding is cement board that was pre-primed then painted about 6 years ago. You can see pictures at the following website: http://home.comcast.net/~pyecomber/paint.htm

I'm wondering if there is anything I can do to prevent this from happening again. Or any recommendations on repainting other than scraping off flaking paint, and using good quality primer and paint.

Thank you in advance for any help!!!

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manhattan42

Where do you live?

I'm thinking acid rain may be the cause, and if so, your first order of business is to re-direct all rainwater from coming into contact with the cement siding.

Until you do, no amount of painting or repainting will help.

    Bookmark   May 21, 2010 at 6:34PM
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sombreuil_mongrel

I don't know who manufactured your fibercement siding, but it is definitely NOT installed according to The James Hardy rules/guidelines, and as such it would not be warranted by the manufacturer.
1) the siding has to be 2" above the shingle /roof line, to avoid being damaged as your is, by the splashing of water.
2) at the bay corner, the flashing allows the water to drip down the corner. I could have flashed this a bit differently to divert the water from the corner, but the real solution has to be a gutter or collector at that point.
The detailing makes the difference. Fibercement products will not stand being constantly splashed or having water flow over like you have.
Casey

    Bookmark   May 21, 2010 at 7:20PM
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susanjf_gw

just as an amature watcher of dozens of how-to shows, i figured out the lack of flashing, the water draining onto the roof instead of completely off...

at least, extend the the drain to the edge and down the side of your home.

i'm surprised you havn't had a leak into the house itself...

    Bookmark   May 21, 2010 at 8:57PM
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santilla

So my builder didn't follow the installation guidelines for the siding. What a surprise. He said he had installed cement siding before, but the way he tried his best to talk me out of it, I was suspicious.

At least now I know not to bother spending lots of time fixing the siding until I add flashing and divert the water differently. Or pay someone to do it. :)

Thank you so very much for the quick and valuable information!

    Bookmark   May 21, 2010 at 10:19PM
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brickeyee

"The paint on my siding is being eaten away, and it appears to only happen in places where rain can either bounce off the shingled roof or run down onto the paint from a roof gully."

Not the shingles but the runoff.

Paint is not designed to have running water on it over and over from roof runoff.

That is a lot more water than even rain itself.

    Bookmark   May 22, 2010 at 2:01PM
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macv

Fiber-cement is not as porous as wood and it doesn't swell as much but it cannot tolerate constant direct water contact. Water does not have to be chemically corrosive to destroy a finish.

    Bookmark   May 22, 2010 at 2:34PM
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