Support Box Trim cathedral ceiling; 24" OC rafter

[littlebluehouse]

Hi all,

I'm new to Hearth.com and also new to installing stove pipes. Installing a Jotul F400 and running the stove pipe through a cathedral ceiling; 5/12 pitch; near the ridge.

anyhow, my rafters are spaced 24" oc. Luckily, where I want to run the chimney/install the support box is right next to a rafter; however, the next is, as you guessed, 24" away. How do I trim out the 10x10 frame without access to the next rafter (I'd really prefer not to take out extra drywall).

Thank you!

 

[DAKSY]

You may have to be a contortionist to do it, but you should be able to run two pieces of framing lumber, 22-1/2" long,
between your rafters/ceiling joists. The challenge is to be able to fasten them.
The best was I've found is with deck screws & a long extension drive in my screwgun.
I start them into the boards & using a small level & pencil to mark a plumb line, I attach
the end I can see first.
Then, I use a speed square to ensure that board is perpendicular to the rafter/ceiling joist &
drive the screws into the far end. Add the smaller member between the two cross pieces
& screw that to them, using your level for plumbness & speed square for perpendicularity.
Hope this makes sense...

 

[littlebluehouse]

Daksy, that does make sense. I was doing some late night pondering and figured that was going to be my best choice. how do you accommodate for pitch to make a level and plumb box? thanks for the reply

 

[DAKSY]

That's where the level comes into play. As long as your line is plumb & you fasten your lumber true to that line,
your ceiling support box will be in the correct position. Frame in your opening & slide your support box in.
It will hit on the low side of the roof sheathing & stop. Attach a magnetic torpedo level to the box & plumb it.
Lightly scribe the pitch of the ceiling on both sides of the box. Remove the box & transfer the scribed lines to
the upper corner & parallel to the originals. Join the lines together across the lower side of the box & cut along
these lines with tin snips. If you did everything correctly, your ceiling support box will fit nicely in the hole, be flush
against the sheathing & perfectly plumb.

 

[littlebluehouse]

great, thank you! yeah I framed it out this morning; not too bad. did find myself contorted to reach those joists but it framed out alright. once I get a dry day I'll take out the roof and drop that support box in. thanks for the advice.

 

[littlebluehouse]

actually, question about the support box; we are using excel ultra black. now, I have my frame using the rafter as one side, with the 3 other stated 2x4's creating my 10x10 box.

however, am I allowed to have the support box right up alongside the rafter/truss? I thought I could but the instructions (http://icc-chimney.com/c/icc/file_db/docs_document.file_en/XLUSA-II_2012-01.pdf) are making it seem like I need to actually come off the truss with a 2x4 to give another inch; not a huge deal, I'd just have to extend my hole and move that cross piece. am I reading into this correctly?

 

[DAKSY]

No need for that extra material. The 2" CTC is built into the ceiling support box. Look at the pic below,
right out of the Excel Installation manual: