We have a large, old, dark, dirty, very unattractive, fieldstone fireplace in our 100+ year old house. It is made of rough and ugly stones in random disorder. It is topped with a concrete mantle. It is floor to ceiling and at least 8 feet wide with a ordinary sized firebox which looks ridiculous in the large stone space. We would like to keep the firebox but would like to disguise, cover over or otherwise improve the appearance of the stone. The stones stick out as much as two feet from the wall in places and the surface is very irregular. Taking the fireplace/chimney out is not an option (expensive and goes through the second and third floors). Any thoughts?

My first thought would be to frame out(past the most protruding rock). You have several options available at that point. You could either dress it in wood (exception of near the firebox), tile or another more attractive stone or a combination of either. Your firebox most doubtly will be recessed somewhat so you need to incorporate that into your overall design that you are not putting comustionble things adjacent to that. When you frame out you can also cover the mantle with a more pleasant faux mantle. Just food for thought.

That will be a tough one to change. How about cleaning the stone? Won't be easy, but nothing you do to it will be easy.

Just looked into a stacked stone product for my own fireplace made of brick. Your situation is tougher because of the protruding stone but there are lots of newer options out there with stone and brick that are 1 to 1 1/2 inches thick. I would go to a local store that specializes in tile/stone and carries this product and see what they can suggest. They may be able to suggest products and installers who can help you solve this issue.

This might be a way to get your stone cleaned up without making a mess of your house.

http://en.wikipedia.org/wiki/Dry-ice_blasting

Google it and you can find contractors in your area that can do it.

If the stone upstairs isn't the same, it's possible someone has put up some facing over the original brick. If the stone at the outside corners appears thin, say 3/4" or 1", you've got artificial rock facing. Probably over red brick.

I don't know if that helps you much. Sometimes, that stuff can be knocked off with chisels and hammers, so the fireplace appears less massive. You can use a grinder and cup wheel to smooth out the surface a bit, knocking down high points, before you patch the whole thing over again with stucco, or some such product.

You see, it's a lot of work, no matter what, but the situation really isn't hopeless. The firebox size remains the same, but you might be able to make the overall appearance more pleasing anyway.

Of course, you may also be able to change the size of the firebox. I've seen that done, but that depends on the chimney, and anything like that gets into some major redesign that needs some expert engineering, and of course, a series of inspection visits during the project.

The least onerous route may be to leave the existing face stone in place, and stucco over it. This increases the apparent mass of the fireplace, which may be counter to what you want.

Good luck.