Double wall wood pipe clearance

[ilikefire1234]

How are you supposed to be meet the 6" distance requirement from combustibles for double wall pipe with ceiling joists, roof rafter and roof plywood sheathing? Rafters and joist are 16" oc so you have a 13" space. 6" double wall pipe is 7" thick so that leaves you with a total of 3" spacing on all sides of the double wall pipe. Specs also state: "8" from top of horizontal run of ceiling" so I think this means it requires a gap of 8" instead.

Would this mean one would require a metal box type contraption that goes from the first floor joist all the way until its 6-8" sticking outside the top of the roof? A bit confused here.

 

[begreen]

It sounds like the installation needs a cathedral ceiling support box. This has zero clearance and internally holds the chimney pipe 2" away from any combustible. Got a picture or two of the location to verify?

 

[30WCF]

Is this cathedral or attic space?

Double wall stove pipe never passes through any of the materials listed above.

You need to put a ceiling box in and go to class A chimney with a 2” clearance.

 

[Eman85]

I think you are confusing double wall stove pipe with class A chimney.

 

[ilikefire1234]

Its a cathedral space, its a cabin im designing so its not built yet, but just ceiling joists (no 2nd floor), then the roof rathers @ 45 degrees, then the plywood sheathing... then metal roofing.

And yes looks like I am confusing double wall with "class A" which appears to allow 2" gap for combustible so that should work. Not sure what the difference is between class and and double wall, I guess the Class A just has a larger air gap and insulation inside this gap, vs normal double wall that has no gap.

Should I just use class A for the section that touches the floor joists and penetrates the ceiling then switch back to normal double wall? Gotta make a list of parts and make sure they fit with eachother. "Allfuel" has a 4ft section for $182 on amazon www.amazon.com/AllFuel-HST-Stainless-Insulated-Chimney/dp/B08TGN7S2N ... The ceiling floor joist to the roof is about 4ft, so Id likley need to get this plus another small piece on top.

 

[30WCF]

Scroll through the pictures in this advertisement for a ceiling box kit. You’ll need one for double wall stove pipe if thats what you are using between the stove and ceiling kit. This one is for single wall.

Cathedral Ceiling Kit for 6" Chimney Pipe with Spark Guard - ComfortBilt

Our cathedral ceiling kit includes all the components necessary to connect single wall stove pipe to double wall Class-A chimney and vent it through a cathedral ceiling. For detailed installation instructions check out our Cathedral Ceiling Planning Guide. Or view the installation instructions...

comfortbilt.net

 

[30WCF]

Mine has an attic, so my ceiling kit is a little different, but the idea is my box is mounted right to the wood ceiling joists, and the box holds the spacing while providing a chase for the pass through. It also
Is the transition from the stove pipe to the chimney pipe.

 

[Eman85]

The ceiling floor joist to the roof is about 4ft, so Id likley need to get this plus another small piece on top.

You said it's a cathedral ceiling with no attic. Then you say you have ceiling floor joists which would sound like there is an attic.

If it's a cathedral ceiling where the rafters are covered by ceiling and roof then you use a cathedral support box and the class A sits in the box and outside. You use double wall which is just 2 walls of pipe no insulation from the stove to the class A. If you have an attic space then you use a box that sits in the ceiling rafters and class A sits in the box and goes up through the attic and above the roof.

 

[Wildflush]

Easy way to remember black pipe (double wall) what you see inside. In your case stove to ceiling box. Class A stainless what you don’t see inside (attic and outside).

 

[begreen]

It's unfortunate that double wall can describe many different types of pipes from a range of applications. There's double-wall stove pipe, chimney pipe, pellet vent pipe, and gas vent pipe. They are all very different from each other with different construction, application, clearances, temperature range, etc.

This is the essence of what it sounds like will need to be installed for this application. The stove pipe is everything below the support box. Stove pipe is also called connector pipe. In this case they show single wall connector with 18" clearance.

 

[ilikefire1234]

The ceiling floor joist to the roof is about 4ft, so Id likley need to get this plus another small piece on top.

You said it's a cathedral ceiling with no attic. Then you say you have ceiling floor joists which would sound like there is an attic.

If it's a cathedral ceiling where the rafters are covered by ceiling and roof then you use a cathedral support box and the class A sits in the box and outside. You use double wall which is just 2 walls of pipe no insulation from the stove to the class A. If you have an attic space then you use a box that sits in the ceiling rafters and class A sits in the box and goes up through the attic and above the roof.

Sorry for the confusion. It is a cathedral ceiling, but it has widely spaced rafter ties (ie: floor joists) that are nailed to the rafters to help keep the roof rigid - these will likely be spaced 32" OC. There is no attic.

 

[begreen]

The cathdral roof support box will establish 2" clearance from the chimney pipe. It can go right against wood. They come in varying depths. This can help provide shielding until past the ceiling rafters. The rafter tie is a different issue because it's usually much lower. The options there are to locate the cathedral support box against the in-between rafter. I think that will put the double-wall stove pipe 8" away from the rafter tie if this is a 6" flue system.