We’ve had enough trouble with the draft of our wood stove flue that we decided to extend the chimney.
A “proper” chimney requires a minimum height above the roof, or roof line—opinions differ—to create the correct amount of draw to pull smoke out of a fireplace or wood stove. The magic number appears to be 3 feet, either above the roof or the ridge of the roof.
Since our chimney exits the roof a couple of inches below the roof line, we decided we could fudge this detail a bit, and satisfy both requirements.
The new, extended chimney (Photo: Mark A. Zeiger).
The last straw came when we last swept the chimney, just over a week ago. We don’t like this chore (see Putting Off the Hardest Chore) but we’ve learned our lesson: do it early, and do it thoroughly. Michelle removed a significant amount of ash from the wood box of the stove, which changed the draw.
We’ve experienced this in the past, and have learned to be aware of the possibility that making too much space in the box might change the draw. It wasn’t too bad, after cleaning, but we did need to take additional steps to get the fire burning right before relaxing and letting it burn.
We decided to add a new section of Metalbestos insulated stove pipe to the chimney, to extend it a bit and increase the draw. Incidentally, there’s no asbestos in Metalbestos, it’s “rock cotton!”
This raised the question of how to proceed. We have a couple of 3-foot lengths of stove pipe under the cabin, which came with the property. Using these would be much more frugal than buying a new section, but it would also be more length than we actually needed. I had two concerns: adding too much windage to the chimney, through excess length, and creating a problem for sweeping. Thus far, I’ve been able to sweep the chimney while seated on the roof line. With additional height, I might need to stand up to do it. A shorter addition might make that less of a problem.
Eventually, we decided to purchase a new 18″ section to add on. All we had to do was bring it home, and wait for the right weather.
It came Saturday. We had a day of no rain or snow, and light wind. The roof was so dry I was able to walk right up, using the safety line as a back up. I screwed the new piece in place, tightened the band, and we were set. Michelle lit a piece of paper to test the draw just as the breeze started up, and we saw we’d done well.
New, extended chimney (detail) (Photo: Mark A. Zeiger).
Now, we’re watching and waiting. I left the safety line up until the next wind storm, just in case it blows over or loose, but I think we’re okay. The instructions that came with the box specified the need to guy the chimney if it exceeds 5 feet. We’re well short of that, and should do fine. Now, we just need to adjust our expectations: we’ve lived here almost 14 years with a short chimney, so it looks weird now that it’s taller. It won’t be long before we get used to it, I’m sure. Meanwhile, our draw is much better!
(For a “before” photo, see A Successful Bargain Hunt.)