I have an external structure Im using to House my smoker.
The roof is 20mm plywood (shed felt on outside) ... I really need to put in a chimney to allow free flow out of smoke ... a 2€� pipe would be enough ... though could be bigger, dont really want bigger than 4€�.
Needs to able to let smoke out and stop rain coming in ....

Anybody think of a fitting that I can use ... simple flange fitting would be ideal ....