How to install 10x10 square ceiling support box in 24OC rafter cathedral ceiling?

[musician235]

Greetings Everyone,

How would I go about correctly installing a square cathedral ceiling support box (Excel) measuring 10"X10" in between two 2X6 rafters spaced at 24 OC? The instructions only explain how to install at 16 OC, so I'm wondering if I should be framing a 10"X10" opening perpendicular to the rafters with two 2X6's, or if there is a different way to do it.

Many thanks in advance. Hoping to accomplish without having to tear the ceiling apart too much.

-Joel

 

[DAKSY]

Go here...

https://www.hearth.com/talk/threads/support-box-trim-cathedral-ceiling-24-oc-rafter.171903/

 

[Ludlow]

I had the exact same install. I used 2x10's perpendicular to the rafters and cut the rake angle into it top and bottom. Then I had a 2x6 block on each side to nail or screw to the rafters (you need to make your plumb cut per roof pitch). I had to cut the drywall out to properly frame to the rafters. Dont know if you have that. If you cut carefully, you can pop the drywall piece right back and tape and mud it and you will never know. I premade the framed box and after cutting the drywall out, I slid the frame box up into the hole and fastened each side to the rafters. I used framing cleats in some areas to make it easier. You will need to do your calcs pretty accurately as to existing roof pitch.

View attachment 235645

 

[Ludlow]

Mine was 12x12 though. But the process is the exact same. Once the framed box was fastened in and I was ready to cut the roof out, I used a long drill bit and drilled up through the decking and shingles. Made cutting the hole very easy and precise.

 

[Highbeam]

Whoa, no need to cut such a huge hole! You only need to cut out enough to provide the 2" clearance to combustibles. Usually we locate the cone flashing centered over the center of the chimney and reach inside the cone from above and mark the oval on the roof deck.

Here's my framing. I would never just toenail or nail this in. Need to use proper joist hangers.

 

[bholler]

Whoa, no need to cut such a huge hole! You only need to cut out enough to provide the 2" clearance to combustibles. Usually we locate the cone flashing centered over the center of the chimney and reach inside the cone from above and mark the oval on the roof deck.

Here's my framing. I would never just toenail or nail this in. Need to use proper joist hangers.

You do not need joist hangers unless you are changing structure like you did. Toenails done properly are plenty to support a chimney.

 

[Ludlow]

Whoa, no need to cut such a huge hole! You only need to cut out enough to provide the 2" clearance to combustibles. Usually we locate the cone flashing centered over the center of the chimney and reach inside the cone from above and mark the oval on the roof deck.

Here's my framing. I would never just toenail or nail this in. Need to use proper joist hangers.

The hangers were used to attach the center block only, after the box was built and installed. It made screwing the sides into the rafters easier. There was no big hole. The drywall was cut out to each rafter because they were 24" centers.

 

[AlbergSteve]

Whoa, no need to cut such a huge hole! You only need to cut out enough to provide the 2" clearance to combustibles. Usually we locate the cone flashing centered over the center of the chimney and reach inside the cone from above and mark the oval on the roof deck.

Here's my framing. I would never just toenail or nail this in. Need to use proper joist hangers.

Nicely done. I would have doubled up the two out side ceiling joist because you're transfering the load of the flue and the cut joist to them.

 

[Ludlow]

You do not need joist hangers unless you are changing structure like you did. Toenails done properly are plenty to support a chimney.

Again, there were only hangers on that center piece. Id like to see anyone get a toenail or a screwgun back into that cavity without cutting the drywall back to the rafter. His question is about 24" centers. That framing was necessary.

 

[bholler]

Again, there were only hangers on that center piece. Id like to see anyone get a toenail or a screwgun back into that cavity without cutting the drywall back to the rafter. His question is about 24" centers. That framing was necessary.

I do it all the time without cutting drywall. The joist hangers comment was directed to high beam saying you needed to use them. In his case he was changing structure so they were needed. But in most cases they are completely unnecessary.

 

[Ludlow]

I am trying to figure out the big hole comment. The roof pic up top was tight to the support box. Just looks larger because of the rake angle. When I say tight I mean it slid in with no play and was dead nuts level in the bottom of the support box.

 

[bholler]

I am trying to figure out the big hole comment. The roof pic up top was tight to the support box. Just looks larger because of the rake angle. When I say tight I mean it slid in with no play and was dead nuts level in the bottom of the support box.

Yeah no problem with the hole. We do that if we are near the bottom of the roof then extend the box up to the roof.

 

[Ludlow]

Yeah no problem with the hole. We do that if we are near the bottom of the roof then extend the box up to the roof.

My ceiling is my roof. It isnt a truss with space between the two. No wonder you can get your hand back there to screw. I was working in the 5 1/2" space of a 2x6. What kind of construction does the OP have I wonder?

 

[bholler]

My ceiling is my roof. It isnt a truss with space between the two.

So yes absolutely cutting the hole like you did is what I would have done. I just don't cut out the drywall. I have no interest in repainting their ceiling.

 

[Ludlow]

So yes absolutely cutting the hole like you did is what I would have done. I just don't cut out the drywall. I have no interest in repainting their ceiling.

I hung 12 feet of class A from that box.

 

[bholler]

I hung 12 feet of class A from that box.

Ok not sure what that changes.

 

[Ludlow]

Ok not sure what that changes.

I just didnt want to hang that much weight on a few blindly run screws back in the cavity. If it was 16" rafter centers it would have been different maybe. The OP asked about 24" centers.
Add to that the difficulty of jamming full dimension lumber 22 1/2" long into a 12x12 hole as you suggest. (The OP has a 10x10, even more difficult with 24" centers) Again, if it was scissor trussed, things would be more doable. Or, one could cut more decking out from above if they wanted to avoid a little tape and mud work, as an alternative.

 

[bholler]

I just didnt want to hang that much weight on a few blindly run screws back in the cavity. If it was 16" rafter centers it would have been different maybe. The OP asked about 24" centers.
Add to that the difficulty of jamming full dimension lumber 22 1/2" long into a 12x12 hole as you suggest. (The OP has a 10x10, even more difficult) Again, if it was scissor trussed, things would be more doable. Or, one could cut more decking out from above if they wanted to avoid a little tape and mud work, as an alternative.

I am perfectly confident in my ability to frame it that way. It isn't that much weight and the shear strength of each screw I use is 1800lbs. I am fine with 3 of them on each end.

 

[Ludlow]

As long as you are satisfied. You must have a very small cordless drill.

 

[Sodbuster]

For the non-pro I think joist hangers at about $1 a piece are an inexpensive peace of mind. Never heard anyone complain that structure was overbuilt.

 

[musician235]

Thanks everyone for the responses. Any thoughts on weather using some angle brackets like in the attached photo would be a suitable compromise between joist hangers and toenailing? So I would only need to open up the 22.5" space and fasten everything from the inside of that one stud bay.. I have a 2x6 cathedral ceiling, a steel roof and inside the sheetrock is covered with 6 inches of foam, 1x4 strapping, and then pine paneling so trying to do all of this from one stud bay without tearing everything apart. There won't be a lot of chimney to support but I do want to make sure it's sturdy enough..

 

[bholler]

As long as you are satisfied. You must have a very small cordless drill.

Yes a right angle one and a straight corded one i always predrill the holes ahead of time and put the camera in the opening so i can see what i am doing.

 

[Ludlow]

Thanks everyone for the responses. Any thoughts on weather using some angle brackets like in the attached photo would be a suitable compromise between joist hangers and toenailing? So I would only need to open up the 22.5" space and fasten everything from the inside of that one stud bay.. I have a 2x6 cathedral ceiling, a steel roof and inside the sheetrock is covered with 6 inches of foam, 1x4 strapping, and then pine paneling so trying to do all of this from one stud bay without tearing everything apart. There won't be a lot of chimney to support but I do want to make sure it's sturdy enough..

That is what I used (on the center one only) because it was put in after the premade frame was installed. My drill is just too big to get in there. Like I said, I premade the entire frame, nailed it all together, then slid it up between the rafters. Then nailed it into the sides of the rafters. Then I test fitted the box and installed the center jack to fit. Then drilled up through the four corners and cut out the roof deck.

 

[Ludlow]

Box dropped in.