Question: I have a 1911 house with an old gas log fireplace. It has an opening 21" deep, 34" across the front, 29" across the back and 29" tall. The flue is 8"x8" clay tile. Do these measurements prohibit wood burning? Answer: No, they have nothing to do with wood burning. The flue seems a bit small for the opening size of the fireplace, but if it is tall enough then it may draft fine. It was very rare for a fireplace to be built for just gas in those days. Chances are it was built for coal or wood use. If the wood smokes (because opening is too large), consider installing a stove/insert in it or closing the size of the opening down. Edit: The cross section of the flue should be 1/10 the fireplace opening size.