you said you want to install a woodburning stove, did you mean like an airtight wood heater or a pot belly stove or? a as fireplace maybe? so then why restore the brick fireplace as well?
If you want to use this flu, then you might also want to check out if it has a smoke shelf. the burnt debris can fall upon the smoke shelf and collect there. with mine I removed a lot of this debris which is completely hidden from sight. some of them have cleanouts , like a plate outside the house. some have a plate so you can shoved the debris down and then clean the ash out downstairs. I have the ash dump but I just remove it from the firebox.
If you are installing an airtight wood stove check your local fire regs and your insurance to avoid surprises. with mine I can retain the fireplace, it's grandfathered but if I were to install a big stove that I can burn wood in and connect that to the flu then I'd have to tangle with fire insurance and bylaws and local building codes and may find it impractical or impossible. Your mileage may vary depending how strict they are where the house is. if you plan to put wood above the firebox the codes state some dimensions you have to adhere to and since this is new work it should follow current code.
My suggestion is to be clear where things are going because you dont want to get part way through and then find building codes or fire insurance issues stop you after you have invested.
This link tells a bit about how chimneys work and the different styles. it shows where the smoke shelf is that you may not be aware exists. I'd put on safety glasses and stick a light up there and see what you find. with mine I found I could get a vacuum cleaner hose up above the smoke shelf and sucked a whole lot out from there by wagging the hose about until there was no no more in there to collect. that partly burned debris can cause a chimney fire if it gets burning so best to clean it out.
some chimneys have flues that have been added, and some are just brick. one issue with the air tight heaters is that you have the ability to choke the fire and make it burn all night but this can also build up the creosote. a fire can burn which is constntly rich in fuel and starving of air and that will create more creosote than a free burning fire.
the burnt debris at the back of the fireboz changes depending on the fire. If the fire is nice dry old fruitwood or similar, and you let it turn to embers, this is clean burning and not starved of oxygen and then youll see the fire clean the firebox. If you run it rich in fuel and starve the oxygen you'll see more carbon, its basically unburnt fuel. what happens in the firebox with the soot ins an indication but what you dont want is a 1/2" cake of stuff building in there, or worse a situation where the chimney plugs up. That's a lot easier to do if the fire is choked , some put doors and things on there and that can create the same situation. Id rather loose some heat and have a good draft and a free burning fire myself, although I do admire the old pot bellies and such.
If the fire burns freely as intended it mostly cleans itself but it also depends on the wood and the kind of fires you have. nice dry hardwood or fir is best but I know I burn any lumber scraps etc as well in mine. I just won/t burn painted wood or particleboard. some fireplaces were built small and expanded when coal went out of favor so the users could burn wood instead. Mine was increased in depth with another row of brick. It seems ok still I use it a lot. I wouldn't give up your right to have a fireplace if it exists now.
http://www.damasonry.com/learn/the-secr ... -fireplace
