I think I have what may be a HUGE fireplace problem. The space between the brick(landing for a lack of a better word) and the inside of the fireplace is about a 2 inch gap and after poking around i found that, that space has collected ashes and such and has burned through part of my subflooring. I have manged to bust away the mortar and brick to expose the gap. My question is. What's the bet way to repair this? I have not been under the house to see if it is visible, if so I can repair the wood that way.. then fix the rest from above.. but if I cant reach the fireplace from underneath, what's the best way to secure the floor so that I can lay brick to seal the top part of the gap.