Thread: Asphalt shingle discoloration - rusted nails?

I came across this roof on a one year warranty inspection but had no idea what the cause was. Could it be rusting of the nails, which are not exposed that I could see? I noticed the same problem on the neighbors house.

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It's hard to see how 1 year old galvanized nails would rust. Did you carefully pry up a tab and look?

My guess is that it's either some sort of droppings or natural wood residues from overhanging trees. Caterpillars leave a similarly colored stain when their poo hits the roof. Maybe other things do also. Looks also like the staining that results from the tannins present in the leaves and wood of hardwoods like oak.

Thats a good guess. Was there any attic area where you could see the nails from the inside. Were the heads rusted. Did you lift a shingle.

Scott,

Are there tress where birds can roost in this area?

I step blew up 200-400-800 + and could not detect nails. Lower center tad stain on top looks circular but still no nail.

Mineral granules with small Iron content?Green Highways Partnership - Sustainable Transportation, Stormwater, Stewardship, Ecosystems, Recycling Boiler Slag (Shingle Granules) has Iron Oxide as component.

I blew up the picture as well, good thing you took it in a large format. It stays clear up to around 600 x's.

I could not see any nails. I like the bird poop theory, but most of the time bird poop that will stain will have a purple color or white mixed in with it. It is possible that the aggregate could have some iron oxide or some similar type rock that is causing the stain. I think a company called TAMKO had this problem several years back, it could have been CeloTex as well.

The roof in your picture looks like an Owens Corning product, I think it is called Berkshire.

Another thought is that it could be from a man made environmental problem. Any industrial plants or any plant with smoke stacks in about a five mile radius, look up wind. I have seen a few roofs and cars down in South Mississippi (Petal, MS) that were near a resin manufacturing plant, they all had finish damage from the stuff being pumped out the smoke stacks.

Could the bundles have been on property for a while?
Stacked, waiting..... someone lays some metal on top..... it rains.... metal rusts....stains.

Far fetched? yep.... but.........

Yes, this is an interesting one. Thanks for the ideas. The attic was accessible and I did not see any rusting from the inside. Nor did I pull up the shingle to see how the nails looked. Maybe I should have but I was worried about possible damage. This sub is only a year old and has no trees large enough to overhang yet. But it is possible that some birds may have caused it, or even the idea of the environment causing it. There certainly may be some industrial plant nearby I am not aware of. And lastly it certainly could have been discolored while waiting around to be installed. Since the next door roof was also affected, one of these generalized theories seems more plausible. Thanks guys.

Originally Posted by Scott Dana

Yes, this is an interesting one. Thanks for the ideas. The attic was accessible and I did not see any rusting from the inside. Nor did I pull up the shingle to see how the nails looked. Maybe I should have but I was worried about possible damage. This sub is only a year old and has no trees large enough to overhang yet. But it is possible that some birds may have caused it, or even the idea of the environment causing it. There certainly may be some industrial plant nearby I am not aware of. And lastly it certainly could have been discolored while waiting around to be installed. Since the next door roof was also affected, one of these generalized theories seems more plausible. Thanks guys.

Scott,
Looking at those stains, I thought my black olive tree might have moved to Georgia!

Are there any trees near the home?

Nope, new sub and nothing overhanging the roof at all.

Ummm, oooolives.

Here is a similar rust/spot issue.

The Dom,

The Rusty Tail Poopie Bird lives in Longwood as well as GA.