You can do it the way you suggest although it may be difficult to attach the plywood (near the firebox opening you can use cement board which meets the code requirements for non-combusitble materials). However, I would suggest that you use mortar, and trowel it on in a sufficient quantity so that it fills up the irregularities and mortar joints and you end up with a reasonably smooth surface. You may have to do it in two coats - first partially filling in the recesses and then a finish coat - the reason is that otherwise a thick coat may sag before it dries. Then you will end up with a surface that is perfect for adhering stone or ceramic tiles to (and it won't stick out into the room as far as a plywood overlay), or even dry wall if you use lead or plastic anchors. This assumes that the existing stone has not been coated with something that will cause the mortar not to stick. If it has, you can use fortified thinset mortar, although it is messier to work with. Hope this helps. Also, since it's 15 feet high you will need a sturdy ladder or even scaffolding (cheap to rent) since the mortar is heavy and you need leverage to apply it.

I've used Brick-anew on a couple of fireplaces and have found it to be a great solution for ugly brick. The reason I've used it more than once is because the 'painted brick' comes out looking like real brick. I was a little apprehensive the first time I used it and was thinking that it sounded too good to be true, but found that my fireplaces turned out much better than I had hoped for and it really does look like real brick. Everyone I have recommended it to has been very happy. Hope this helps - It is sure easier and cheaper than other fireplace remodeling solutions. Good Luck! Here is a link that might be useful: Brick Paint

Nothing yet. Still original Brick. I just painted the brick and it looks new now. Dont have $1000 to spend on fixing the fireplace I dont use. I use wood stove now.

"That should cut it nearly flush with the other brick." And make it stick out like a sore thumb. Score slightly if you must then snap it off. If you get a bad break,you can try and clean it up or get a plugging chisel and drilling hammer (small sledge) and take out the whole stone. you might get lucky and find out the stones are only a few inches into the wall and easy to remove. You can ten use the piece to fill the hole. This post was edited by brickeyee on Thu, Mar 21, 13 at 14:45