cathedral ceiling support box questions

[michael-p]

Hi -

I'm installing a wood stove in a cathedral ceiling, with a 2:12 roof pitch. From interior to exterior the ceiling is: tongue and groove paneling, 2x6 rafters, 1/2 plywood, ice and water shield, and shingles. I am using selkirk supervent and have the ceiling support box. The ceiling is still open from the bottom, so I have options as to what order I do things. After reading some of the threads here, I have a few questions:

1. Should the hole in the roof plywood sheathing be square to pull the cathedral ceiling support box all the way through? Or, is it better to cut a round hole in the plywood sheathing with clearance for the stove pipe and keep the ceiling support box completely below the roof sheathing? In that case I'll have to trim the box down. It seems to me it's better to cut a square hole so I have access to nail the support box to the framing from the inside.
2. What is the most efficient order of operations for lining everything up and installing the support box? My prelim thought is to put the stove where I want it, run a plumb line to the underside of the roof sheathing, mark center, draw the square for the support box on the roof sheathing, frame around that, then drill through the roof in the corners and cut the hole from the top of the roof, put support box up, then do the interior paneling around the box once it's in. But i'm not sure that's the best way to keep everything lined up and make the process as painless as possible.
3. Probably a dumb question but - if the ceiling support box is level, and the roof is sloped (2:12 pitch) then the square hole for the ceiling support box would need to be larger than the the support box right? How do you figure this out or trace the right size hole of a horizontally level square into a pitched ceiling?

Thanks!

 

[Nate R]

Hi -

I'm installing a wood stove in a cathedral ceiling, with a 2:12 roof pitch. From interior to exterior the ceiling is: tongue and groove paneling, 2x6 rafters, 1/2 plywood, ice and water shield, and shingles. I am using selkirk supervent and have the ceiling support box. The ceiling is still open from the bottom, so I have options as to what order I do things. After reading some of the threads here, I have a few questions:

1. Should the hole in the roof plywood sheathing be square to pull the cathedral ceiling support box all the way through? Or, is it better to cut a round hole in the plywood sheathing with clearance for the stove pipe and keep the ceiling support box completely below the roof sheathing? In that case I'll have to trim the box down. It seems to me it's better to cut a square hole so I have access to nail the support box to the framing from the inside.
2. What is the most efficient order of operations for lining everything up and installing the support box? My prelim thought is to put the stove where I want it, run a plumb line to the underside of the roof sheathing, mark center, draw the square for the support box on the roof sheathing, frame around that, then drill through the roof in the corners and cut the hole from the top of the roof, put support box up, then do the interior paneling around the box once it's in. But i'm not sure that's the best way to keep everything lined up and make the process as painless as possible.
3. Probably a dumb question but - if the ceiling support box is level, and the roof is sloped (2:12 pitch) then the square hole for the ceiling support box would need to be larger than the the support box right? How do you figure this out or trace the right size hole of a horizontally level square into a pitched ceiling?

Thanks!

1: I screwed mine in by reaching inide the box from inside, so roof hole was round-ish. I believe the instructions tell you to leave the box against/below the roof sheathing.

2. Sounds good to me.

3. At 2:12, it's not too crazy to just trace around the box with a pencil while holding it level. The metal trim pieces can hide a fair amount.

 

[Eman85]

Hi -

I'm installing a wood stove in a cathedral ceiling, with a 2:12 roof pitch. From interior to exterior the ceiling is: tongue and groove paneling, 2x6 rafters, 1/2 plywood, ice and water shield, and shingles. I am using selkirk supervent and have the ceiling support box. The ceiling is still open from the bottom, so I have options as to what order I do things. After reading some of the threads here, I have a few questions:

1. Should the hole in the roof plywood sheathing be square to pull the cathedral ceiling support box all the way through? Or, is it better to cut a round hole in the plywood sheathing with clearance for the stove pipe and keep the ceiling support box completely below the roof sheathing? In that case I'll have to trim the box down. It seems to me it's better to cut a square hole so I have access to nail the support box to the framing from the inside.

Been a while since I installed mine but from memory I cut the hole square and dropped the box in from the top, I think the box had a flange that supported it on the roof deck. Then I attached to the framing as you said from inside the box.

2. What is the most efficient order of operations for lining everything up and installing the support box? My prelim thought is to put the stove where I want it, run a plumb line to the underside of the roof sheathing, mark center, draw the square for the support box on the roof sheathing, frame around that, then drill through the roof in the corners and cut the hole from the top of the roof, put support box up, then do the interior paneling around the box once it's in. But i'm not sure that's the best way to keep everything lined up and make the process as painless as possible.

You have an advantage as you say the ceiling is open, I had to work with a ceiling. Your method sounds right. Measure 4 or 5 times before cutting.

3. Probably a dumb question but - if the ceiling support box is level, and the roof is sloped (2:12 pitch) then the square hole for the ceiling support box would need to be larger than the the support box right? How do you figure this out or trace the right size hole of a horizontally level square into a pitched ceiling?

Thanks!

That's a good question and I don't remember how I did it. Mine came with a trim piece that hides the edge and allowed for some oversize.
If it's 2/12 you will have to make sure you have a tall enough chimney to get a good draft. Where is the chimney compared to the ridge? You will have to put supports on the chimney to get it tall enough.