Overbuilding a chimney to surpass NFP 211

[Hoytman]

I want to hear your thoughts and suggestions.

Codes often change.

If you were to build a new chimney and wanted to over build it to surpass existing codes to handle coal and wood, how would you do it? Or, would just rely on existing codes?

Keep in mind it hasn’t been too many decades ago when most chimneys were built with a large flue, which shrank to about 8” I.D., and has since shrank to 6” for most modern stoves.

I’m interested in ingenuity here. “Outside the box” or “building a better mousetrap” type thoughts and comments. Think structure and/or insulating properties, sizing and height, materials, etc.

[Rob R.]

The 10/2 rule should be viewed as a minimum requirement, not a design target. For best performance the chimney should go up through the structure rather than outside it, and extend past the peak of the roof.

Masonry is the best choice for coal, but 316 stainless has proven to work pretty good also.

[nut]

Over built mine. 16" square blocks in the center with 8" flue liner. 4 " air gap and then an 8" concrete block surround for a 4 feet x 4 feet outer chimney surround. Outer and inner connected together with wire reinforcement every 3 courses. Only complaint is I should have made it 2 flues. About 40 feet high through the center of the house.

[coalder]

The only way to "overbuild" something as simple as a chimney would be to line it with firebrick instead of using a common flue. That is the way chimneys for kilns, incinerators or any other extreme high temp exhausts are built. Now chimney blocks are out of the equation & a brick veneer would be required. This would be a ridiculously expensive way just to compensate for utter stupidity.

Jim

[Hoytman]

Pictures are allowed in this thread. LOL!

Jim, I had the same thought as you with the fire brick lining which leads me to another question you may or may not be able to answer. I wonder what the regulations are/were for industrial chimney stacks in America and England, how much heat that had to be able to withstand and what type of bricks they were made of? They do not appear to be modern "firebricks", but I could be wrong. At least that's the idea I get of watching steeplejacks like Fred Dibnah on youtube taking them down.

[nut]

40 years ago I had a mobile home I heated with a small coal stove. I used metalbestos stainless double wall chimney pipe. Both regular and coal rated. I burned it so slow (you could grab the pipe) to keep from roasting us out that both sets rotted out in a 9 year period. When I built my house with it's masonry chimney I had a heavy duty stainless steel cap custom made and that too rotted out. My experience is not good with stainless.YMMV

[coalder]

Before codes & before flues most chimneys were built of common brick. These were clay bricks baked at a very high temp & thus,were able to withstand moderate to high temps. There were several brick yards along the Hudson river, but were all shut down sometime in the 1960's because their kilns were fired by coal. Thus the end of a the true common brick. So most likely any early chimneys you see being torn down, were of common brick. As far as regulations, it's hard enough to keep up with them here much less globally. But suffice it to say that anything commercial today, is scheduled by an engineer. Try to imagine the boiler size required for a hospital & the safety factor of the chimney. This ain't gonna be a simple flue lined chimney!! The engineer is gonna spec the boiler..s & spec the chimney. Guaranteed to be firebrick lined, somewhere in the neighborhood of 4 ft square laid up with a speced out refractory mortar ect. Never worked on one myself, but have spoken with different union guys who have, & given me quite a perspective on just how involved these commercial chimneys are. So, when I hear about over complicating a simple residential chimney.............Just makes my head hurt.

Jim