Hello: I am a diy and am relocating a gas fireplace. It backs on an outside wall with one floor joist parallel to the wall under the fireplace. The joist is 2x10 x25ft. Beneath is a wall on an concrete basement floor that crosses at 18ft, 2x4 with no header but shimmed at the top( its a finished basement so it’s hard to see what is what) The base of the fireplace is centred on the 25ft span and is 20 x 77 inches. A lot of the construction is fastened to the wall with 4 inch screws to the 12ft peak. So far it weighs about 700lbs but I have yet to apply a stacked stone floor to ceiling finish. How much further in weight can I go? Should I build a concrete footing beneath in the basement?