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Thank you for the advice in advance. I have a 1 1/2 story home with a central chimney that has two flues installed. The main level has a gas log fireplace and the other flue runs to the basement where there are concrete footings from floor to ceiling underneath the main level fireplace to support the weight of the stone and hearth above. The flue that runs to the basement is a 5" inner diameter with an air-cooled outer diameter of 7". I am assuming this runs to the top of the chimney 35' up. I was hoping to install a wood-burning fireplace in the basement; however, it looks like this will require an 8" insulated flue at the least and more likely a 10" ID insulated flue with the size of fireplace we would like to use.

My question is - how hard is it to exchange the 5" ID for a 10" ID insulated flue? It appears that the opening in the chimney is at least 12" for this flue. Who would be best to do the job if I need help? thanks again

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first thing to understand is gas appliances use different materials and protocols than wood burning appliances. they are not interchangeable.

if you have a preexisting ceramic flue or stone flue thats large enough for the new liner, then it should be pretty simple. if its going into a ceramic or stone flue, it doesnt need to be double walled in the chimney, just if it passes out into the room (as a lateral or vertical connector). its pretty common here in ontario to use 8in or 10in flexible stainless flue liner pipe to do these type of retrofits. however, it could be smaller for a smaller unit. some zero clearance units have exhausts of 6in.

if you have to install a new larger flue, it will be very costly and invasive as it will essentially mean replacing the entire chimney column from the basement flue port up to the roof.

i would start with calling a licensed fireplace installer to come have a look.

  • The flex pipe is easy to install but not legal in Oregon for wood burning because it loads up with creosote and creates a fire hazard. A licensed pro would be the best way to go for advice (get an estimate they are usually free) then you can decide if the scope of work is something you can do or if you should have it done. – Ed Beal May 15 '16 at 19:39

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