2 fireplaces, 1 flue - smoke leak

MD, United States   

I have 2 fireplaces, 1 on 1st floor and 1 directly below it in the basement.

Both are on the same flue/chimney. When I have a fire upstairs there is significant smoke seepage into the basement. The only solutions that worked were a chimney balloon, with limited success and need to re-inflate constantly, and current mode of sealing it up with insulation panels/caulking.

That’s a short-term fix. Would love to use this fireplace but the balloon is a mess to insert/remove constantly. Would new doors with gaskets work? Currently has the standard glass bi-folds (pro baby builder grade).

Looking to stop the seepage but keep the fireplace functional. Willing to do some adjustments on use each time but chimney balloon is not idea.


Note: This isn’t an issue with priming, I’m well aware of doing that properly.


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by Home Saver Chimney Sweeps | November 29, 2016
Catawissa, Pennsylvania

Very common problem. There is always a negative pressure in the basement of any house. Gets worse during heating season due to the “stack effect”. Heat upstairs naturally flowing up draws air in from below. Chances are both flues are the same height and if capped makes it even worse. Creating a vacuum in the basement by creating heat upstairs plus a fireplace can remove up to 550 cubic ft of air per minute from a dwelling and the smoke being drawn into the basement flue from the stack effect is your problem. One fix is to have the upstairs flue extended. This will allow the smoke to flow and not be drawn into the other flue. The other is to have a lock top damper installed on the basement flue which will completely stop any smoke being drawn in.

by ChimneyChick | November 29, 2016 ChimneyChick's avatar
Midland, Ontario

Totally agree with HomeSaver, took the words right out of my mouth re negative pressure in the basement unit.

Install a Lock Top sealing Damper at the top of the basement fireplace to totally seal off the top when not in use

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