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Hi Robert,

Here's what probably happened. The crown on the original stack cracked and infiltration turned the top of that stack into an unsteady pile of Jenga blocks. The owner got an estimate, said, "What! That's too G__D____ much to pay to rebuild the top of that stack; I'll fix it myself," and he then went out, bought a bag of Sackrete and set to work throwing away all of the loose bricks and troweling on the existing crown. When he got done he congratulated himself on how he outwitted those crooks who call themselves brick masons.

I'd tell 'em it needs to be restored to it's original condition and height.

ONE TEAM - ONE FIGHT!!!

Mike

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Bill,

My problem with this diagram is that it does not make clear where to measure from. Is it the top of the flue, the top of the bricks, or the top of the crown?

From the IRC:

1003.9 Termination. Chimneys shall extend at least 2 feet (610 mm) higher than any portion of a building within 10 feet (3048 mm), but shall not be less than 3 feet (914 mm) above the highest point where the chimney passes through the roof.

CHIMNEY. A primary vertical structure containing one or more flues, for the purpose of carrying gaseous products of combustion and air from a fuel-burning appliance to the outside atmosphere.

So from this, I read it as measuring from the top of the bricks -- maybe the top of the crown. But definitely not the top of the clay flue. Would that be your interpretation also?

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Bill,

My problem with this diagram is that it does not make clear where to measure from. Is it the top of the flue, the top of the bricks, or the top of the crown?

From the IRC:

1003.9 Termination. Chimneys shall extend at least 2 feet (610 mm) higher than any portion of a building within 10 feet (3048 mm), but shall not be less than 3 feet (914 mm) above the highest point where the chimney passes through the roof.

CHIMNEY. A primary vertical structure containing one or more flues, for the purpose of carrying gaseous products of combustion and air from a fuel-burning appliance to the outside atmosphere.

So from this, I read it as measuring from the top of the bricks -- maybe the top of the crown. But definitely not the top of the clay flue. Would that be your interpretation also?

Actually, the measurement should be taken from where da smoke comes out.

You are correct that the diagram from the NFPA is not clear. There are other illustrations from official sources, including one that appears in some recent editions of the IRC, that clearly shows the top of the flue liner as the "termination" for measurement.

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Actually, the measurement should be taken from where da smoke comes out.

You are correct that the diagram from the NFPA is not clear. There are other illustrations from official sources, including one that appears in some recent editions of the IRC, that clearly shows the top of the flue liner as the "termination" for measurement.

Well, I agree that makes sense, but I don't think that's what it says. Maybe the IRC language should be changed.

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The applicable section is titled "terminations". Therefore, the actual termination is the flue gas outlet and not the crown. You can have a chimney ten feet wide with the flue closest uphill being several feet away from the uphill face that is less than 36" from the roof deck yet the flue gas outlet is greater than 36" so it meets the spirit of the code.

The intent of the code is twofold in this rule:

First, it is ASSumed that a hot spark or ember will cool and self extinguish if it falls at least 36" before landing on a combustible roof, hence the 36" min.

Second, the 2/10 is designed to place the flue gas outlet above a positive pressure zone created by wind rolling over the peak of a roof or bouncing off a nearby wall or structure.

Now, this code is not foolproof since all codes are minimum standards. You can exceed them. Just because a chimney complies with 3/2/10 does not guarantee performance.

That flue tile extends a bit too high above the crown. Although 211 now only requires a min. of 2" above the crown and no longer restricts the projection, functionally, it should not exceed ~6" exposed.

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LOL Bill. You can tell them I said it was a good practice. No code reference limiting the height. Actually, clay pots are not addressed in the code. They do not attach directly to the preceding flue tile so it really is not part of the "flue". It isn't a rain cap because its open. Yet they are allowed because they've been around a few hundred years.

The problem with too much exposed uninsulated flue liner is that it cools rapidly thereby causing excessive creosote build up and possibly hindering draft. Once you more than about half of a tile above the crown wash, it becomes unstable.

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The applicable section is titled "terminations". Therefore, the actual termination is the flue gas outlet and not the crown.

The applicable section is titled "chimneys". The definition of chimney, as I read it, does not include the flue liner, which is not part of the "primary vertical structure". Maybe that was the intention of the code writers -- I don't think they did a good job in this case of translating their ideas into the written word. Maybe others think that the flue liner is part of the primary vertical structure. I don't. I think the flue liner goes inside the primary vertical structure.

At any rate, this is a huge non-issue. Believe me -- I understand how much of a non-issue this is. I'm only engaged in an academic exercise.

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The applicable section is titled "terminations". Therefore, the actual termination is the flue gas outlet and not the crown.

The applicable section is titled "chimneys". The definition of chimney, as I read it, does not include the flue liner, which is not part of the "primary vertical structure". Maybe that was the intention of the code writers -- I don't think they did a good job in this case of translating their ideas into the written word. Maybe others think that the flue liner is part of the primary vertical structure. I don't. I think the flue liner goes inside the primary vertical structure.

At any rate, this is a huge non-issue. Believe me -- I understand how much of a non-issue this is. I'm only engaged in an academic exercise.

In the 06' IRC, it's 'termination':

R1003.9 Termination...

Marc

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