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Masonry chimney clearance from wood framing (C) Carson Dunlop Associates Masonry Chimney Fire Clearances from Combustibles

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Chimney fire clearance distances between masonry & wood framing:

This article describes the fire clearances required for masonry chimneys. The distance between a brick, stone, concrete block,or other masonry chimney and the nearest combustible material, such as wood framing, is an important fire safety consideration that must be respected.



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Masonry Chimney Indoor Fire Clearances from Combustibles

Masonry Chimney Fire Clearance from Wood Framing

Masonry chimney clearance from wood framing (C) Carson Dunlop Associates Masonry chimney clearance from wood (C) Carson Dunlop Associates

As Carson Dunlop's sketches (above) illustrate, proper masonry construction leaves space between wood framing members and the chimney, or where framing rests on or in a masonry chimney, at least 12" of solid masonry should separate the chimney flue from the nearest wood framing member.

Readers of this article should also
see CHIMNEY HEIGHT & CLEARANCE CODE for details such as chimney clearances from roof surfaces or nearby building walls and windows.

This article series on chimneys, chimney construction, and chimney safety provide detailed suggestions describing how to perform a thorough visual inspection of chimneys for safety and other defects.

Inspectors of older homes often find wood framing built right against masonry chimneys and at times we find wood framing that rests in a pocket in a masonry chimney structure, using the chimney to support the building framing.

Reader Question: air leaks around chimney passage through ceilings

First of all - Congrats on a very extensive website!

In looking for air leakage in/out of our attic, I had a look at where our chimney passes through the ceiling. I found a couple of what could be problem areas:

- On one side of the brick, there is a 2x4 that butts up against the brick
- On another side, there is 2x4 beam that is about 1" from the brickwork.

The first beam could be removed but requires demolition of one interior wall
The second is structural and cannot be easily accessed.

The chimney serves a Heatilator fireplace below. Exterior dimensions are 17" x 22". I believe it has claytile flue.

This is a 60's home. A few questions:
- Are there any grandfathering rules that might allow the 1" clearance?
- would it be acceptable to replace the 2x4 that is in contact with a steel 2x4 ?
- Would it be possible to install some fireproof material between the 2x4 with 1" clearance and the chimney?

Our only other options seem to be to abandon using the fireplace or perhaps convert it to a gas (propane) fired fireplace.

Any words of advice?

Reply:

I've seen people use various noncombustibles as sealants: refractory cement, fire-proof caulks, fire resistant foam sealant spray around masonry chimneys at ceiling passages. Certainly I don't like seeing wood in contact with the chimney though that was indeed a common practice back in the days before we even had fire departments. <g> If you are sealing around a metal flue, check with the chimney system manufacturer about its use before closing any air gap. Keep me posted. Daniel

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