Just wanted to know what would be the best method to add on to my existing hearth. Currently our fireplace is built into the corner of our den room but the hearth does not extend to the side walls of the room. There is about 1 1/2 feet of empty space on either side of the heart. I want to extend the length of the hearth so that the length of the hearth goes from wall to wall in front of the fireplace.

My questions are:
1. Is there any building code on how far away a hearth has to be from an existing wall?
2. Should i use cement to extend the heart up to the walls (we have a cement foundation)?
3. Should i use backerboard to raise the floor level at the end of the existing hearth and then re-tile the whole length of the hearth?

Any advice or suggestion are greatly appreciated and a special thanks in advance to all.