How hot does the outside of a tile lined block chimney get? The block looks to be 1-1.5" where it passes through the floor. The sweep says it is not a problem, the exterior of the block will not get that warm. There are no permits needed for install in our town. just want it to be absolutely safe.
temp of a tile lined chimney
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There are a lot of answers to that questions.......
CURRENT standards (NFPA) call for 2" clearance for interior chimneys and 1" clearance for exterior chimneys.
However, it was common practice for many years (and approved by many local jurisdictions) to have wood almost touching masonry! Some earlier standards were 1/2" to flooring or trim, but 2" to framing members (Canada in the 80's).
Ok, so to answer your questions....
The outside of a block chimney does not get very hot in normal operation. But, in theory, it is possible that it could get very hot in the case of a sustained chimney fire or something like that.
Safety it ALWAYS a matter of degree. 3 inches would be even better than 2", and 1 7/8" may be just about as safe as 2. There are many variables including the exact construction of the chimney, the appliance being used, etc. - but codes have determined that in order to be as safe as possible in the worst possible situation, the 2" is needed.
Your sweep may be "informally" correct in that there is no immediate problem. However, by the letter of the code (which does apply even though you may not have access to an inspector), your unit may be deficient (along with millions of others)......
A lot of this stuff is "muddy" because it has changed over the years in response to more folks using wood, and people in colder climates using (and abusing) their chimneys. That is why Canada came up with stricter chimney standards before the US did.
CURRENT standards (NFPA) call for 2" clearance for interior chimneys and 1" clearance for exterior chimneys.
However, it was common practice for many years (and approved by many local jurisdictions) to have wood almost touching masonry! Some earlier standards were 1/2" to flooring or trim, but 2" to framing members (Canada in the 80's).
Ok, so to answer your questions....
The outside of a block chimney does not get very hot in normal operation. But, in theory, it is possible that it could get very hot in the case of a sustained chimney fire or something like that.
Safety it ALWAYS a matter of degree. 3 inches would be even better than 2", and 1 7/8" may be just about as safe as 2. There are many variables including the exact construction of the chimney, the appliance being used, etc. - but codes have determined that in order to be as safe as possible in the worst possible situation, the 2" is needed.
Your sweep may be "informally" correct in that there is no immediate problem. However, by the letter of the code (which does apply even though you may not have access to an inspector), your unit may be deficient (along with millions of others)......
A lot of this stuff is "muddy" because it has changed over the years in response to more folks using wood, and people in colder climates using (and abusing) their chimneys. That is why Canada came up with stricter chimney standards before the US did.
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