Hi folks, I've attached an old picture of one side of my workshop to help explain. Please ignore the positions of items as everything has moved since taking the picture, except the coke forge which is still in the same position.

I want to install a wood burning stove for taking off the chill in the air when the forge isn't lit. I would like to position the stove close to the forge, pretty much where the gas forge is in this picture.

To save cutting another hole in my tin roof I'd like to branch the stove flue into the forge flue. My forge flue is single wall 1mm spiral ducting that's 12" diameter. I don't know exact measurements off the top of my head but there's about 6 feet of flue inside the workshop before it goes through the roof, and about the same again outside which takes it a couple feet above the peak of the roof.

Assuming that I can use spiral ducting again for the wood stove, can anyone tell me if there's rules of thumb that I should be following?

I.e is there a flue diameter which will work best going into the 12" forge flue? Is there an ideal height the two should connect? Is there an idea angle the two should connect at? 45 degree bends are readily available.

I remember when I was doing my reading into forge flue heights a few years ago that there was a lot of science in it that went completely over my head, so I thought I'd better ask about this before I go cutting holes & accidentally create some thermo dynamic chaos and ruin the draw of both the forge and wood stove.

Cheers for any pointers.

good rule is to not share the flue.

your shop your call

Not sure what the rules are for your area, but over here the International Mechanical Code prohibits two solid fuel burning appliances from sharing a single chimney.  I believe that that would apply to a coke forge and wood stove.  Please check with your local authority having jurisdiction to ensure compliance and recognize that if local code is violated in an installation your insurance may be invalidated in case of a loss.

19 minutes ago, Steve Sells said:

good rule is to not share the flue.

Certainly true if both were running simultaneously. Not sure if that would still be the rule if only one of them were ever going at any given time, especially if there were some kind of built-in valve that would only allow one flue to be connected at a time.

1 minute ago, Latticino said:

Please check with your local authority having jurisdiction to ensure compliance and recognize that if local code is violated in an installation your insurance may be invalidated in case of a loss.

Always good advice.

Consider placement of woodstove near an outside access point ( window or door )  hauling wood deep inside a room is a real pain and dirty