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Smoke in basement from upstairs fireplace

Posted by mjolson5 (My Page) on
Mon, Nov 21, 11 at 21:43

I have a 1965 home with an up/down fireplace (both flues in one chimney). We've always had a problem with smoke from the basement fireplace when we are using the upstairs fireplace. A recent inspection showed many cracks in the upstairs flue joints. The chimney company repaired the cracks with cerfactory (sp?) cement saying that was the reason for the cross-smoking. Well our first fire today and smoke again! I'm at a loss. The fireplace has a fresh air inlet and both flues have Chimilator top mount covers. The basement's is closed.

Any ideas??

Follow-Up Postings:

RE: Smoke in basement from upstairs fireplace

Oh my goodness, I could have written this myself! I have the same set up and same problem. We had the upstairs flue relined and new dampers put on both. Our downstairs one is also closed. Nothing has worked. I have been reading about chimney heights and think mine is too short. Smoke is getting trapped between the chimney (side of house) and a valley in the gabled roof. I am having a mason come out and look into extending it, but also to make the upstairs flue taller than the basement one. This is supposed to help with the draft and get rid of negative pressure. I hope it works. I'll let you know what the mason says.

RE: Smoke in basement from upstairs fireplace

The problem has little to do with the similar height of both flues; you shouldn't be getting a downdraft down either one of them if the chimney was built properly. If you have an exterior chimney with the flue opening (top) lower than the lowest interior part of your home, you will definitely have problems. The stack should actually be a bit higher than the highest exterior (ridge line of roof) portion of the home - especially on an exterior chimney. It is sad that so many builders and masons don't know and often don't care about the proper functioning of a chimney. the 10/2 rule is a minimum requirement for a builder to pass code, NOT a recommendation on what SHOULD be done. Nothing other than extending the stack to its proper height will solve your problem permanently - and if the mason or "chimney professional" you hire says othewise, FIRE HIM. This is why the poor original poster spent lots and lots of mony to no avail - she dealt with chimney professionals more interested in selling her unnecessary liners than understanding and fixing the real problem.

RE: Smoke in basement from upstairs fireplace

Well, problem solved. Our ancient model of Chimilator wasn't sealing well and we were indeed getting a downdraft into the basement. The chimney repair guys formed a gasket to improve the seal and now the problem is gone.

RE: Smoke in basement from upstairs fireplace

The "problem" is solved because he sealed the damper, but you wouldn't have had a downdraft in the first place if the stack was the proper height for your home.

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