selkirk chimney install issues.

[jeepin in maine]

i'm getting ready to install my 4300 steptop and have run into a small issue with the chimney.i built my hearthpad and non combustible wall with the stove being configured to reduced clearances.this allows the back of the stove to be 7" from a non combustible wall,and the back of the pipe connector to be at 10".so........with a 1" air space,1/2" durorock,and tile+ 7" to the back of the stove,3" to the back of the stove pipe connector,another 3" to the middle of the 6" stove pipe connection,+ 1" extra...i marked the center of the hole i need to cut in the ceiling at 16" away from the wall.
the selkirk kit requires a 12 3/8" hole in the ceiling,and heres where i ran into trouble.i put a long screw up thru the ceiling and went up into the attic to check things out.i figured i'd have to offset the pipe from center to avoid the ceiling joists and roof trusses,and i will....about 4" which is no biggie.the problem arose when i realized that with my 5/12 pitch i don't have enough room to install the attic insulation shield.if i'm reading it right it sits on top of the rafters,and then i need 12" of room between the top of the joist,and the sheathing on the roof for the shield to fit.i have no where near that,and if i move the ceiling opening enough that i do,my stove will be sitting wayyyyy to far out into the room.
so what are my options?can i mount the attic shield to the bottom of the rafters instead of the top?my joists are 6" and so is the insulation,so if i mount the box below the rafters,i'll have 12" of shielding for the 6" insulation.is this allowed?
i saw in the manual that you can skip the shield and enclose the pipe to protect it from the insulation,but theres zero room up there to frame anything.i'm hoping to start installing the inside stuff tonite so any help or ideas will be appreciated.thanks.jeremy

 

[jeepin in maine]

anyone have any ideas?

 

[jeepin in maine]

no one else has had a similiar issue?

 

[aussieblake]

I know this not anything you want to hear but I am going to throw it out there. Assuming you have drywall on your ceiling, you could cut a larger hole in the drywall than you originally needed. That would allow you to frame up a box to from underneath to act as your insulation barrier.

When you installed your ceiling support box, don't you cut an oversized hole? One that is 2" larger all the way around, could you buy some 12" or 14" snap lock HVAC duct from the HD or Lowes. Cut it to fit between the roof deck and ceiling to act as you insulation shield might want to cut a few vent holes in it. This could also be installed from the roof once the hole is cut in the roof.

Another thought, since you will be cutting a hole in the roof could you frame it on the roof? Once you cut the hole in your roof will the attice insulation shield up into the hole in the roof allowing it to clear? I realize you with have flashing there just a thougth.

And at last, you could cut the attic insulation shield around the middle, into two pieces. This would allow the top to slip over the bottom and basically making it adjustable, and screwing it together to stabilize it, or just trim the bottom down until it rests at the right height. You may hear lots of groaning about this one because it modifies a UL listed part.

Remember the idea is to keep all combustibles (including insulation) 2" away from the chimney pipe.

These are just ideas. I have never tried them, just some brain storming.

aussieblake

 

[jeepin in maine]

"And at last, you could cut the attic insulation shield around the middle, into two pieces. This would allow the top to slip over the bottom and basically making it adjustable, and screwing it together to stabilize it, or just trim the bottom down until it rests at the right height. "

i had this same thought.just wondering if its legal?

Another thought, since you will be cutting a hole in the roof could you frame it on the roof? Once you cut the hole in your roof will the attice insulation shield up into the hole in the roof allowing it to clear? I realize you with have flashing there just a thougth.

this seems like an idea also....is it legal to pass the insulation shield thru the roof and then cover it with the flashing kit?

 

[aussieblake]

If this is being inspected, that would be a questiong AHJ. You may call a few stove shops and talk to one of their installers, they maybe able to answer the question. Again since it only establishes a boundary to keep away combustible materials you maybe better off fabricating your own.

aussieblake

 

[BJ64]

I just built a drop down box to deal with the problem. This situation had a vaulted roof and a 3/12 pitch.
This one drops too much and is rather obvious but on a positive note it did not take much time to make (as you can tell). The front face is about 10-inches vertical. I would have been fine with 6-inches but by making it 10-inches I was able to not need an extra piece of connector pipe.

I am thinking about redoing it in the spring. I thought about adding a small ledge up there for decorations that heat will not bother.

 

[begreen]

One solution would be to use a cathedral ceiling support box. Cut the opening in the roof an fold over a flange like in this picture. Another possibility would be to use sheetmetal flashing to create a continuous shield from the inside of the support box to the roof instead of trying to do it with wood and drywall. Figure #4 is from the Selkirk catalog.

 

[crazy_dan]

I would have to say if it is keeping the insulation off the pipe then it is fine. I would put it on the bottom of rafter and see if it passes inspection. If not I would ask what I needed to do and go from their.

 

[jeepin in maine]

does anyone know if its ok for the attic shield to pass thru the roof up into the flashing a little bit?

 

[DiscoInferno]

I'm possibly going to have the same issue in a month or so when our addition w/ new chimney is built. Since I already bought the insulation shield, if it's too tall I just planned to trim off the top as needed.

 

[Nic36]

does anyone know if its ok for the attic shield to pass thru the roof up into the flashing a little bit?

I don't see how it would matter if it was inside the flashing some. It's only purpose is too keep insulation and debris out. However, the shield is pretty wide. So, to maintain the correct clearance from combustibles, your roof hole may have to be bigger. I don't know if you want to do that.

I personally like the idea of cutting the shield in two pieces and making it adjustable. However, I understand that may cause problems with passing an inspection, insurance, and any manufacturer's guarantee.

 

[begreen]

Look closely at the left diagram from Selkirk. Here's the info for the support box:

The Support Box is intended for use when installing chimney in an A-frame, in a mobile home, or in a ceiling under a narrow section of roof. It provides a finished installation at the ceiling level and will support up to 20 feet of 6, 7 or 8 inch diameter chimney. The part also provides shielding from insulation when installed in an unoccupied attic space. The Support Box assembly is comprised of a black box designed for installation inside 16 inch O.C. joists, a cylindrical shield, support bucket, ceiling trim, and four screws.

Yes, it can be flanged on the roof, under the flashing. Here's an illustration from Simpson's guide: