Ash staining on chimney and metal roof

pantosketcham · Post by **pantosketcham** » Mon. Apr. 27, 2020 12:32 pm

This spring I noticed a visible staining on my roof boot and the metal roofing below it. Kinda a beige'ish color like ash. Despite some pretty good downpours lately it isn't washing off.

I imagine this must happen to others. Any ideas why? Is it cause for concern as far as corrosion goes? Thanks.

Post by **Rob R.** » Mon. Apr. 27, 2020 3:54 pm

It is likely staining from the iron in the ash. Some people have reporting staining/corrosion issues, others have no problems at all. I don't really understand what causes it to be an issue sporadically.

I have never noticed any staining on my metal roof, but the steel has a green coating that would make it tough to see anyway.

pantosketcham · Post by **pantosketcham** » Mon. Apr. 27, 2020 6:33 pm

Thanks Rob.

Hoytman · Post by **Hoytman** » Mon. Apr. 27, 2020 7:33 pm

I have mentioned this several times on this forum and it seems to get down played, at least with regard to anthracite. However, myself and many long time bituminous burners are well aware of this staining.

This year was my first year burning coal of any kind. With a new asphalt roof, and having relatives in East KY coal country, knowing of the staining issues for nearly 45 years, I was a bit concerned burning anthracite and staining my new roof. The verdict is still out.

oliver power · Post by **oliver power** » Mon. Apr. 27, 2020 10:21 pm

I've had it eat holes through the roof panels closest to chimney. I believe this has happened 3 times to my roof. Finally, I fabricated standing seam aluminum roof pans. It doesn't seem to bother aluminum.....

coalder · Post by **coalder** » Tue. Apr. 28, 2020 7:23 am

Your staining is caused because you have a cap on your chimney. Hot gasses go up the chimney, condense on the cap & drip onto the roof. I've seen this over & over, even with masonry chimneys with caps. Had to re top several masonry chimneys in my time because of caps, even burning wood. Hot gasses from wood would condense on the stone cap, creosote would then drip onto the chimney block & over time rot the top block. On a metal chimney a cap is a must & corrosion will always be a by product of burning coal. On a masonry chimney.... ditch the cap!!!
Jim

Hoytman · Post by **Hoytman** » Wed. Apr. 29, 2020 12:18 pm

I've seen it many times in eastern KY and most of those folks never had a cap on their chimney. What's up with that? Bituminous country...

coalder · Post by **coalder** » Wed. Apr. 29, 2020 1:51 pm

Hoytman wrote: ↑
Wed. Apr. 29, 2020 12:18 pm
I've seen it many times in eastern KY and most of those folks never had a cap on their chimney. What's up with that? Bituminous country...

Can't say for sure, as I have never repaired a chimney that has burned bit. However if those roofs were stained w/o a cap; a cap on same chimney would likely produce enough tar to seal a 300 ft driveway.LOL
Jim

Hoytman · Post by **Hoytman** » Wed. Apr. 29, 2020 5:19 pm

All I know is growing up I seen hundreds of rusting roofs in bituminous country. I know it can produce black soot, but didn’t know about tar...wood...yes.

warminmn · Post by **warminmn** » Wed. Apr. 29, 2020 6:07 pm

I have a lot of rust on my shingles from my stainless chimney without a cap. None around my brick chimney which is used less, except on the flashing. But Im betting I would have more if I had caps. Its the nature of the beast.

coalder · Post by **coalder** » Wed. Apr. 29, 2020 8:12 pm

Hoytman wrote: ↑
Wed. Apr. 29, 2020 5:19 pm
All I know is growing up I seen hundreds of rusting roofs in bituminous country. I know it can produce black soot, but didn’t know about tar...wood...yes.

www.wikipedia.org/wiki/tar

Jim

gardener · Post by **gardener** » Tue. Aug. 25, 2020 8:23 am

I am glad to see the subject of coal exhaust and metal roofing discussed.

Perhaps there are not many coal burning homeowners with metal roofing that frequent this forum?

pantosketcham, please update this thread in upcoming years, also if you would post a picture of the issue you have observed this past spring

Rob R. wrote: I have never noticed any staining on my metal roof, but the steel has a green coating that would make it tough to see anyway.

oliver power wrote: I've had it eat holes through the roof panels closest to chimney. I believe this has happened 3 times to my roof. Finally, I fabricated standing seam aluminum roof pans. It doesn't seem to bother aluminum.....

Rob R. and oliver power, back when I looked into getting a metal roof there seemed to be different paints / coatings the material was offered sealed in. I have wondered whether the different experiences people have with coal ash on metal roofing is due to how well the metal if protected by their coatings. I know that even if a metal roof is coated, during installation and normal damage from age the coating is perforated and the metal can rust where it has been exposed. Do either of you know what coatings your metal roof has?

oliver power, the aluminum panel you fabricated, is it painted or coated?

Post by **Rob R.** » Tue. Aug. 25, 2020 9:25 am

Mine is 24 gauge Galvalume with some sort of coating on top. Here is a link in case you want to read more:

https://www.drexmet.com/product-list/100ss-profile

oliver power · Post by **oliver power** » Fri. Aug. 28, 2020 10:09 pm

gardener wrote: ↑
Tue. Aug. 25, 2020 8:23 am
I am glad to see the subject of coal exhaust and metal roofing discussed. Perhaps there are not many coal burning homeowners with metal roofing that frequent this forum?

pantosketcham, please update this thread in upcoming years, also if you would post a picture of the issue you have observed this past spring

Rob R. and oliver power, back when I looked into getting a metal roof there seemed to be different paints / coatings the material was offered sealed in. I have wondered whether the different experiences people have with coal ash on metal roofing is due to how well the metal if protected by their coatings. I know that even if a metal roof is coated, during installation and normal damage from age the coating is perforated and the metal can rust where it has been exposed. Do either of you know what coatings your metal roof has?

oliver power, the aluminum panel you fabricated, is it painted or coated?

I used .032 painted aluminum gutter coil.