The Twisted Fix To Real Victorian Smokers………………………Answer To Mimi’s Question.
Victorian homes had multi-faceted high steep pitched roofs.
The Problem: This created downdraft problems for many of the chimneys. They would release smoke into the house and make house keeping cleaning a real chore.
One solution for this was to extend the height of the chimneys and this meant tall thin, usually freestanding, chimneys from the roof up to heights near to, if not exceeding the ridge of the roof.
This worked mostly, but the right (or wrong) weather conditions would cool these chimneys and cause thermal inversions and make them sometimes hard to light and also drafty. In some of these old homes most of the significant rooms had a fireplace.
Additionally they were subject to weather damage and were dangerous or more difficult to build (read costly). Being thinner (in general) they cooled more easily so they had condensation problems, which manifested itself as creosote buildup (increased risk of chimney fires) and more maintenance repairs.
The Fix: So architects and builders tried to incorporate the chimneys in the body of the roof as much as possible. The optimum plan allowed a chimney to rise to near the ridge and emerge with only the last few feet exposed to the elements.
This worked very well, kept the chimney from excessive cooling, maintenance was relatively low and there were minimal draft problems. Great, but not all floor plans would allow this with straight chimneys.
The Twist: Then the ‘offset flue’ construction of chimneys came about as a way to get the chimney to exit the roof as close to the optimal location as could be achieved. This was achieved by stepping off the successive layers of brick by small increments per layer.
Some referred to this a corbelling and structurally it is closer to cantilevering but here the weight of the masonry above counterbalances the overhang. As any toddler who’s played with blocks can tell you, there are limits as to how far you can go.
The physical realities limit how far the offsets can move the chimney and extended offsets also re-introduced draft problems as well. Fire regulations also limited the number of turns, lengths of runs and combinations of flues in a given chimney body.
So architects and the masonry trade soon learned to work within a well defined set of rules for successful application of this technique.
Look for gradual turns and smaller lateral displacements in proportion to the height rise.
If you have concerns consult with a specialist. ( A chimney sweep, a master mason, or a WETT certified technician. WETT = Wood Energy Transfer Technology.)
This article was written by Robert Butler to answer a comment question from a previous article. ;
Mimi’s Question: I have a question. I specialize in Victorian homes. Many times in the attic the brick chimney stack is a little twisted between the attic floor and the exit at the roof line. Any idea why they did that? The first few times I thought it was the same drunken mason, but it is too consistent, and I have always wondered why.
Original blog post on ActiveRain: Link to Blog Post