I live in a small city and cannot find anyone to give me an answer. The chimney is on the inside, on the hallway wall. It has a base in the crawlspace of 30”L X 26”W X 28”H (to the floor joist). It then is 16.5” X 16.5” to above the roofline. The internal diameter of the clay-lined flu is 6.5” X 6.5” square. Opposite the hallway wall is the living room. I was hoping to make a real small wood-burning masonry fireplace (like a Rumford?) using the existing chimney that served an oil burner that now has been removed. The house is a one-story, 1K sq. ft Is it possible? Can you offer any assistance in how it can be done? Plans? Thanks for the help in advance.