Expert: James Ball - 4/3/2009

Question
I am looking into a job for a lady that has a Brunco 190 wood stove that has an 8" outlet for the stove pipe.  Her contractor installed a 6" thimble into the poured concrete wall, the thimble feeds into a 8" x 8" square clay flu liner.  The Chimney is about 18' tall.  She consistently has smoke being forced back into her house. Does she need a bigger thimble, and is her chimney big enough to handle that much of a wood stove?

Answer
Hello Aaron, a 8 x 8 out side is usually a 7 x 7 inside (cross sectional inches = 49) an 8" round has a cross sectional inches of 50.24) I would say that is ok but you can not down size the thimble, by doing that you have "choked off the draft" and it will smoke, the system must stay 8" all the way. I would have a local Certified Chimney Sweep (www.csia.org, there you can look up by zip code to find one near you) take a first hand look at what you have they should be able to help.
James