Guys, I have my forge built and need to build a chimmey in my pole barn. I have a 12 foot flat metal ceiling, then it's another 6 foot to the roof and I want to go 5 foot past the peak of the roof. I have a chance to get 12 inch dia.x by 10 ft galvanized spiral wound pipe, 3 sections with connectors for next to nothing all being brand new. It is 20 gauge pipe. What is your thoughts on using galvanized for a chimmey? I could use some carbon steel up to about 5 foot straight out of my super sucker hood if you think there is a heat issue. Please let me know your thoughts.

Thanks in advance....

RJ

Galvanized is what I use.  I did snag some stainless for the bottom couple of feet; but haven't installed it or needed it yet.

double up the flue walls at the ceiling /roof penitrations for fire code.

I can't seeing being any issue I really don't think you will get enough heat to do anything with the zinc Coating especially that its a nice and big diameter . We have a fire pit with a chimney over it and we make huge fires in it that you can't even stand by it six feet away and we have a spiral pipe like you want to use and we never had any issues with the zinc .

Lets see in my pole barn the chimney is 6' from any wood, only wood in it is the 4 utility poles that are the uprights, everything else is steel---it was cheaper that way.  Codes differ depending on where you are at and the specific circumstances...

 

Mr Yellow isn't sharing where he is at or even what country he is in.

Sorry,

I'm in Illinois, here in the good ole USA.

My ceiling in my tin pole barn is 12 foot flat metal ceiling, then the slant roof where the chimmey will go thru the tin roof is 6 feet above that. 24 inch centers on the roof trusses.

The concern with galvanized anything is when it reaches a certain temperature, it produces toxic fumes. The good thing is that the temperature this occurs at is pretty high. Magnitudes higher than the chimney should ever reach. Galvanized is fine, so long as a piece never falls into your forge and sits there long enough to change color.