I am looking to construct a 4 sided fireplace in the center of 3 adjoining room; living, family and dining. Looking to use flagstone and brick. How can I assure proper draft and construction?
I'm not sure what your situation is. You said 4 sided in 3 rooms. Will you be able to see into the other rooms through the fireplace? Where does the fourth side face? Is this a common chimney with four fireboxes?
You will likely need a power exhaust on the chimney top. Flues are sized relative to the openning. You have too mcuh openning size for any practical size of flue. You also need to consider where the makeup air will come from