Installing Duraplus support box on low end of cathedral ceiling. Help!

[white91lx50]

I have the stove set about where we want it. I will end up with 6" corner clearance (spec is 4") 30" or so front clearance, and over 8" side to combustibles (the curtain)

My question is how in the world do i get my butt down the roof joist to build frame work for the duraplus support box?! I'm only going to be about 2 feet off the soffit side. I'm about 8 feet away from where i need to get to in the pictures. I will have to go through 2 layers of insulation as you can see from when the house was built, along with 12" plus of blown in insulation. I don't see how i can crawl into the area from the attic space, so do i try and frame it from below after I cut the hole? I don't see any other way. Also, is there a prefab cover for the square support boxes, or do i need to fab one? I don't need mice or other critters getting in there!

Thanks, Will

 

[webby3650]

Frame it from below. We will cut the hole in the roof most of the time so a helper can assist from above. Since you don’t have room for an attic insulation shield, we would use a fire stop to seal off the box. You can also make one from sheet metal.

 

[begreen]

Frame it from below. We will cut the hole in the roof most of the time so a helper can assist from above. Since you don’t have room for an attic insulation shield, we would use a fire stop to seal off the box. You can also make one from sheet metal.

I was wondering if they could use a tall (24'?) cathedral ceiling support box to act as firestop and attic insulation shield. It would go right up through the roof.

 

[white91lx50]

Frame it from below. We will cut the hole in the roof most of the time so a helper can assist from above. Since you don’t have room for an attic insulation shield, we would use a fire stop to seal off the box. You can also make one from sheet metal.

Thanks, I sure picked the wrong time of year to be poking holes in the roof 😂.

If I have room for it, and I think I will, would you recommend getting the 24” tall support box for a little extra height over the 11”. I think it was $15 more.
Even though the top would be covered, my thought was the higher it is over anything to possibly find a way in the better.

 

[white91lx50]

I was wondering if they could use a tall (24'?) cathedral ceiling support box to act as firestop and attic insulation shield.

I’d still have to cover the top. It wouldn’t reach the bottom of the roof at 24”, and I don’t believe you’re allowed to modify the support box per code I thought, so I couldn’t get a 36 and modify it

 

[bholler]

I’d still have to cover the top. It wouldn’t reach the bottom of the roof at 24”, and I don’t believe you’re allowed to modify the support box per code I thought, so I couldn’t get a 36 and modify it

You are allowed to cut it to match the angle of the roof. Or extend it with sheet metal

 

[webby3650]

I’d still have to cover the top. It wouldn’t reach the bottom of the roof at 24”, and I don’t believe you’re allowed to modify the support box per code I thought, so I couldn’t get a 36 and modify it

Sure you can. Use some sheet metal to extend the box to the same pitch as the roof deck.

 

[white91lx50]

Well that works then 👍

On another note, how far off of the truss do I have to be with the box? I know center of them is ideal (ours are 24” o.c.) If i could cheat towards one side it would help a bit with stove placement.

 

[webby3650]

Well that works then 👍

On another note, how far off of the truss do I have to be with the box? I know center of them is ideal (ours are 24” o.c.) If i could cheat towards one side it would help a bit with stove placement.

The box can attach directly to the truss. The support box maintains the proper clearance.

 

[white91lx50]

Before I go poking a hole in the ceiling, is this the correct way to frame for the chimney support box above the cathedral? Trusses are 24” apart. Run two studs (a and b) from truss to truss and make sure they’re level and plumb, then take piece c (x2) and cut to match that angle to drop in and screw to my studs? Thanks

 

[begreen]

Sure you can. Use some sheet metal to extend the box to the same pitch as the roof deck.

Or use a 36" square ceiling support box like DuraVent's Duratech 6DT-CS36. EDIT: See below for DuraPlus.

Before I go poking a hole in the ceiling, is this the correct way to frame for the chimney support box above the cathedral? Trusses are 24” apart. Run two studs (a and b) from truss to truss and make sure they’re level and plumb, then take piece c (x2) and cut to match that angle to drop in and screw to my studs? Thanks

That's one way, but it can also be flanged on the roof by folding down the bottom and side edges. Or a combo of both.

 

[webby3650]

Or use a 36" square ceiling support box like DuraVent's Duratech 6DT-CS36.

He’s using dura-plus though

 

[begreen]

He’s using dura-plus though

Whoops, thanks for catching that. In DuraPlus the part number is 6HTC-CS36.

 

[white91lx50]

Would I be better in switching to double wall duratech or another brand? From all my reading, duraplus can lose some draft vs others? Only reason I’d like to use duraplus is it’s quickly available around me

 

[begreen]

DuraPlus is their value line and triple wall. DuraTech is their premium pipe with better insulation and double-wall for a smaller OD. Excel also makes a very good chimney pipe, but will cost more.