Chimneys that are enclosed with a combustible housing

[hudson144 150]

I have been following the posts and comments on the Montrose Fire, I see that maybe we can all now put whatever thoughts and feelings we have aside and take this situation to the next level. Being familiar with the situation too include who lived in the house etc I feel that if we look at the construction of many of the homes throughout the region this can and will happen again. I have been against the wooden enclosed stove pipes,chimneys or whatever you want to call them for years. I have seen these enclosures burn where sometimes the results were better than the latest that we all have been talking about. I am gonna start by mentioning a few points and I hope that many more points will be brought out to make this a learning experience for all. When you have a pipe enclosed with wood IMO it is not good from the get go. Imagine enclosing a catylitic converter on your car with wood? The results- a car fire! The importance for correct clearance for the pipes is a priority and I am sure and I am anything but a codes guy they have all been established to keep mishaps from happening. I have seen these pipes glowing bright red during daytime incidents and know that if they were against wood or vinyl siding the results would not be good. Cleaning of the chimney pipe or cleanout is important as well. Firespread both vertically and horizontally makes a difference here also. Fire not being discovered right away will also have a large impact on the situation. This situation can happen anywhere,anytime to all of us no matter what dept you are from. I tried to look for pictures of the enclosed wooden chimneys to post with no success and I am sure that some of you out there that are more computor friendly than me can post for this topic. PLease- add to this post so we can all learn from, each fire is different than the other so add to the discussion regardless how minor an incident might have been or an experience you might have been involved with. Thanks JJc

[VAEMC 10]

jjc Great Point! There is a large concern with this issue. The scary part of this is that the fire can advance quickly and spread through out areas of the home where the home owner my not even know, similar to what happen this past Friday. Within the dummy chimney is a vent from the boiler room, which provids natural air flow to the inside of the dummy chimney. As the fire begins to consume the dummy chimney, it builds strength and also begins to spread rapidly through the eves and attack space. Before you know it 1/2 of the structure is involved unbeynounced to the home onwer who maybe inside enjoying a nice fire in the fireplace or sleeping. He/she won't notice the smell because he would most likely attribute it to the fire in the fireplace.

Edited December 24, 2009 by VAEMC

[antiquefirelt 994]

OK, where to begin? First, NFPA 211 the Standard on Chimneys, Fireplaces and solid fuel burning appliances (something like that)requires that all chimneys be enclosed where they pass through "living spaces". Furthermore they may not pass through a closet/storage area.

Proper code compliant enclosures require a chimney to literally be free standing from it's bases through the roof with a 2" airspace between the chimney and any combustibles. This creates a multi-story vertical enclosure that must be fire stopped at every level by a minimum of 22 ga. steel. Most of the time this comes in the form a metal flashing secured to the floor and fitted tight to the chimney. Some exceptions are when the chimney liner is a listed "zero clearance" system such as the pured "Supa Flu" or the newer stainless steel tube liners. In cases where approved "zero-clearance" systems are used, the chimney may be exposed to the living space or the enclosure may be fitted tight to the chimney itself.

Using a standard metal pipe enclosed in a wood enclosure does not meet code. The requisite clearance for standard single wall or unlisted metal pipe is 36". Most newer home use "Metalbestos" or some similar system that allows for the minimum clearance to combustibles. In my former life as a carpenter, we installed these chimney systems and I can tell you that dropping a single section will do damage to the liner and could cause future issues. Still we see many people selling these in local "swap/sell it guides" and there's little guarantee they're safe for use.

I've seen numerous older chimneys that went floor to floor, with the bricks stopping at the ceiling joists and restarting on the next floor above! Thats right a wooden section at each floor. Guess what, each time it was in a 100 plus year old house! No reason they should have lasted but somehow, they did.

For the most part, chimney fires start where the home insulation stops. If the roof is insulated the chimney fire "throat" will be close to the roof line whereas when the top floor ceiling represent the last insulated plane, the throat will be near this point. The point where the smoke reaches the cool chimney flue is where creosote builds up. Some other issues are the older chimneys that are corbeled (not straight). Most older houses had the chimney come straight out through the peak, though the fireplace or flue entrance was not aligned with the peak. These requires building in a slanted section which especially when not lined, is a perfect creosote catcher. These are tougher to clean and clear when burning.

Up my way masons do not have to be licensed so we get tons of poor installations to inspect. Sadly most citizens don't know their right to require the mason to complete a form stating the chimney will be built in compliance with NFPA 211, and end up with little recourse other than court. In Maine it is a class E crime for a mason to fail to provide a homeowner this form, but most don't know that the standard or form even exists. Anyone and everyone with a trowel and strong back is a mason!