We have a double sided fireplace made of irregularly shaped stone. We have problems getting the smoke to rise and not come into the room. We've had it cleaned and the expert said it was in good condition. He said the smoke is not rising either because 1) there is too much open air around the fire or 2) the stack is not high enough. We are attempting to fix the open air issue first before the latter.
The stone is stacked standing up, laying down, and some are even on a diagonal and jet out a bit to create depth. Because of this, the surface is not flat. Also, both openings are square but they do not have perfect edges because of the irregularly stacked design. We've installed new glass doors which were meant for larger openings, but the metal frame still does not cover some of the gaps. Some gaps are large enough to stick my hand through and some I can stick my finger through. Is there a good solution to help seal these gaps? In my dreams there is some type of flame retardant expanding black foam. But I don't know if that would look nice. Any thoughts on how to solve this problem? Also, has anyone ever had to extend their fireplace stack?
Thanks so much for your feedback!