Help with chimney code.

[Doug Campone]

While doing some repair work on a chimney, we discovered what appears to be where the original roofers may have tried to save money.

We're looking at the chimney of two units in a townhouse complex. The flashing and cricket were poorly done and had resulted in a leak. The repairs have been done and when he pulled off the second section of siding he discovered that there was no OSB behind the siding on one side of the chimney, about 24" up from the roof deck. The other issue is to do with the fire stop between the two chimneys (inside). It also stops at the same point.

I can't find anything in the fire code about this and I'd like to have it corrected before it gets closed up again. I suspect that this fire stop should go all the way up and the same with the OSB behind the siding. Any feedback from someone who knows more about the fire code in this situation would be greatly appreciated.

I tried to upload a picture to make this clearer, but that function doesn’t seem to function properly.

Cheers,
Doug

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[Thom Huggett]

Sorry, but I can't follow what the situation is. Is this a masonry chimney or wood frame? Photos would help.

[Doug Campone]

Sorry, but I can't follow what the situation is. Is this a masonry chimney or wood frame? Photos would help.

I know a picture would help and I can't get the picture upload to work - at least not with Microsoft Explorer. Seems to work ok with Google Chrome tho'.

Anyway, here's a picture - hope this helps.

Chimney-s2.jpg

Doug

[Thom Huggett]

I would have expected to see an intermediate stud and the osb extending to the top, but contact the building official who issued the permit to you (you did get a permit, right?) to see what he/she wants to see. Some will ask you to make it right, others will allow you to replace in kind.

[Bob Harper]

This is a *chase* with two factory built *chimneys* housed inside it. Now, each chimney must have a listed firestop at each ceiling level but at the attic level, the firestop sits on top of the joists. The rest of the chase opening around this listed assembly is referred to as "fireblocking". The IRC specifies suitable materials for fireblocking or you can get your AHJ to approve of an alternative material such as sheetmetal if you like. Now, as they sit, there is no requirement I'm aware of to separate the two chimneys inside the chase with vertical fireblocking in any code. The Uniform Code requires vertical fireblocking below the roof deck but the IRC does not.

Can you clarify your question and do you have other pics inside the chase?

[Chris McIntyre]

Bob has covered the fire code/chimney questions, as for the wood frame chase it would need to be treated like any other wall with vinyl siding applied. Solid substrate (OSB) weather resistant barrier and flashing.

[Doug Campone]

Bob has covered the fire code/chimney questions, as for the wood frame chase it would need to be treated like any other wall with vinyl siding applied. Solid substrate (OSB) weather resistant barrier and flashing.

Thanks everyone for you responses. It pretty much what I expected. On this complex we have only found one chase which was missing the support (OSB), behind the siding and most of them had the underlayment paper installed vertically instead of layered horizontally - begging for a leak.