Im not sure I understand what you mean by a 3 sided 13x13 tile around a 36" fireplace. Could you explain.

If by three sided you mean putting the tile on the two sides and above the firebox, I think that would look fine. I personally don't like a lot of small tiles on a fireplace. As an aside, 13"x13" tile is a strange size - it's usually 12"x12" or next up is 16"x16". Also, if your fireplace is 36" and you put 13" tile on both sides that adds up to a 62" width which means the tiles would be 2" wider than your mantle shelf. I think that would look funny, the edge of the tiles should match up with the edges of the bottom of the shelf. You can trim the tiles with a cheap tile saw to the exact width if they really are 13".

ventupete, you are correct on the three sided tiles.

Is it possible to get a custom mantle? For example, we all know the bottom of a mantle shelf is shorter in width. Maybe I can get that at 62"(to match tile/firebox), and the top of the shelf will be 70"?

Now our fireplace is located on a wall that is 15 feet wide. 72" of the wall sticks out 6" from wall(to fit the firebox). Should I just get a 72" mantle shelf, even though the bottom shelf of mantle will be slightly longer than tile/firebox?

Thanks for all your help here!!

Anything is possible, but usually when you get into custom sizes it costs more. Mantle shelves are not hard to make if you have any woodworking skills. Have you thought about doing a surround (vertical pieces on each side that support the mantel shelf) or do you not like the look? That would frame out the tiles and eat up the rest of the 72" fur out. You could also get the 72" shelf and do a strip of contrasting tile on the edges to match up with the edge of the shelf. Lot of possibilities. If you send me your e-mail address I'll send you a picture of what I built in our 13' ceiling living room. ventupete at aol dot com.

If you check out a post entitled "Anyone have pictures of their overmantel" from March of '07. I posted the picture there