What sort of wall is concealing the chimney? Dry wall will come down quick. You might be lucky and find a masonry masterpiece. If not then the repair pricing will be determined by the amount of work involved.

The wall where the old fireplace would have been is plaster, so it's a bit more labor intensive to open it up and see what we're dealing with. Although if we didn't have a large bookcase anchored to the wall right where I'd need to look, I'd be tempted to drill some large pilot holes and poke around a bit.

That is a great idea, though, and probably the best way for us to figure out a little more of what's going on in there without a big commitment.

You're right. If there is only one chimney, it was for the central heating system, not a fireplace.

Today is the big reason I will never have another fireplace. Right now it's 1 degree outside and my woodstove is keeping the house at a nice toasty 70 degrees.

Another possibility would be a prefabricated gas fireplace. Much less weight, so no need for footings, etc. There's no reaon why the old chimney would be involved in this, either. Gas burning appliances require a different chemically resistant flue. If there is sufficient space, one could possibly run alongside the existing brick chimney. Another caution is this: in most states you would be required to meet all current codes and fire regulations if you make modifications to an old chimney. This would mean lining and separate flues for the existing boiler and water heater at a minimum unless they are already in place.

The chimney inspection is your first step, this should be completed annually just to confirm that the existing appliances are venting properly. This will answer most of your questions regarding separate flues, size and condition. Your budget will determine the most effective solution of an added fireplace, there are some zero clearance options that could be installed without a lot of structural modifications. Mostly gas appliances, unless you want something in the basement/cellar. Contact a Certified Chimney Sweep so you know that the information you receive is accurate and reliable. $75 for an initial inspection sounds pretty cheap, check qualifications, insurance certificates and references. In the Midwest a typical inspection with video is $180-200.

Wow, thanks for all the wonderful responses. Seems like reality is raining on my parade a bit. But there's lots of great information here. As akamainegrower suspects, the chimney is not one of those big chimneys--it's only about 3' by 3'. Technically there is a second chimney at the back of the house as well, but that begins where the kitchen is (and I think the kitchen has always been in the same spot) so perhaps that second one was for an old kitchen stove?

I'm intrigued a bit by the gas appliance possibilities--although I love a wood fire, gas seems like it might be more possible. A wood stove would be a great option, but unfortunately our rooms are fairly small and I can't really picture any spot where a wood stove could fit if it were standing out from the wall. There's really only space for something that fits into an existing cavity. However, there may be space next to the existing chimney. I seem to recall that, years ago, I heard of some kind of fireplace system that could be installed with some kind of pipe chimney instead of a masonry chimney? Meaning it could more easily be retrofitted to run up the interior of a house? Perhaps I'm completely misremembering.

DK and Sons, thanks for the top about the recommended annual inspection. I hadn't realized these were recommended even where the chimney is not used for a fireplace. I'll have to look into that, and check whether this company is reputable or what the work usually costs in my area.

I have rebuilt many of these style chimneys, they usually have multiple flies inside them. Your mileage may vary.

Definitely have someone come in and inspect the chimney. It isn't worth pursuing without knowing if there are structural problems, which could be very expensive to pursue.