Figuring out chimney support (ceiling box or roof)

[GaryOR]

So I'm trying to figure out what the least hassle method of supporting the chimney is in the new install for our Morso 3440. Single story house, stove in the NW corner of the living room (both outside walls), 4/12 pitch roof. Aiming for about 15' of total pipe (Morso's recommendation) even though it means I'll end up with about 8' of Class A sticking out of my roof since we don't have high ceilings or much attic to pass through at that point.

My dilemma is this -- the corner of the house where we're installing the stove is literally on the far end, opposite corner of the house from my attic access. Normally not a big deal, right?

The previous owners did some major insulation upgrade before we bought the house and there's (I'm not kidding here) 20-24" of white, fluffy blown-in insulation and I'd really rather not wade through all of that if I didn't have to. (Or deal with trying to re-fluff and even it out it when I'm done)

I've spent a few weeks searching / perusing older Hearth.com threads and it seems like anytime the roof-mount chimney support comes up as a topic, there's a handful of responses along the lines of "they work, but I prefer the standard ceiling-mount support box."

It seems to me that using a roof-mount that nails/screws to the roof decking would make my life easier since all the work would be done from either the roof or down in the living room.

Can anybody help me understand the potential issues with the roof-mount or just a general explanation of why they're not that popular?

Of course, if there are any other suggested solutions (or comments about the install in general), I'd love to hear them.

Thanks!

 

[bholler]

So I'm trying to figure out what the least hassle method of supporting the chimney is in the new install for our Morso 3440. Single story house, stove in the NW corner of the living room (both outside walls), 4/12 pitch roof. Aiming for about 15' of total pipe (Morso's recommendation) even though it means I'll end up with about 8' of Class A sticking out of my roof since we don't have high ceilings or much attic to pass through at that point.

My dilemma is this -- the corner of the house where we're installing the stove is literally on the far end, opposite corner of the house from my attic access. Normally not a big deal, right?

The previous owners did some major insulation upgrade before we bought the house and there's (I'm not kidding here) 20-24" of white, fluffy blown-in insulation and I'd really rather not wade through all of that if I didn't have to. (Or deal with trying to re-fluff and even it out it when I'm done)

I've spent a few weeks searching / perusing older Hearth.com threads and it seems like anytime the roof-mount chimney support comes up as a topic, there's a handful of responses along the lines of "they work, but I prefer the standard ceiling-mount support box."

It seems to me that using a roof-mount that nails/screws to the roof decking would make my life easier since all the work would be done from either the roof or down in the living room.

Can anybody help me understand the potential issues with the roof-mount or just a general explanation of why they're not that popular?

Of course, if there are any other suggested solutions (or comments about the install in general), I'd love to hear them.

Thanks!

I usually dont use roof supports mainly because a support box is easier. Even with a roof support you will still need an attic insulation sheild and some sort of ceiling passthrough box which installs pretty much the same as a support box. So i see no reason to add another step.

 

[moresnow]

20-24" of insulation. Argh. No fun! Might as well just get up there and get it done. Gotta go up in there anyway as mentioned.

 

[begreen]

It's a pain, but I agree with bholler. Fortunately you only need to do it once. 8' of chimney sticking out of the roof will need a support brace at 5' past the roof exit.

 

[webby3650]

On a low pitch down low like you are describing, I often don’t need to get in the attic. There’s no room to work anyway. If yours is like most, a cathedral ceiling support box will extend all the way to the roof deck, acting also as the the insulation shield.

 

[bholler]

On a low pitch down low like you are describing, I often don’t need to get in the attic. There’s no room to work anyway. If yours is like most, a cathedral ceiling support box will extend all the way to the roof deck, acting also as the the insulation shield.

We do the same. If it doesnt reach i usually extend it so it does in cases like this.

 

[GaryOR]

On a low pitch down low like you are describing, I often don’t need to get in the attic. There’s no room to work anyway. If yours is like most, a cathedral ceiling support box will extend all the way to the roof deck, acting also as the the insulation shield.

We do the same. If it doesnt reach i usually extend it so it does in cases like this.

To make sure I understand what you're both saying . . . . .

Cut the roof hole first, work through it (rather than crawling through the attic) to install the ceiling support box -- and at the same time, use an extension on the support box to keep the insulation away rather than installing a separate insulation shield.

Do I have that correct?

Based on my measurements and probing through the living room ceiling it looks like I've got ~19" of height in the attic between the top of the drywall that makes up the living room ceiling and the bottom of the roof decking.

Just extend the support box up to the roof decking on the low side of the pitch and leave the rest open to the attic or cut the extension to follow the slope of the roof?

In either case, do I need to fab up a sheet metal "cover" for the top that would take the place of the storm collar that would top the normal insulation shield to keep crap out of there or is it just left open to the bottom of the roof flashing?

Thanks for the help! I'll run off and start another thread about the double-wall stovepipe questions!

 

[GaryOR]

20-24" of insulation. Argh. No fun! Might as well just get up there and get it done. Gotta go up in there anyway as mentioned.

I'm not complaining about somebody else having paid for the efficiency upgrade -- but I won't argue that it makes it a whole lot more difficult to move/work up there than our last house that only had ~R-20 insulation in the attic!

I think webby3650 and bholler have pointed out the obvious answer; my brain was just locked on the "have to crawl around in the attic" part.

 

[bholler]

To make sure I understand what you're both saying . . . . .

Cut the roof hole first, work through it (rather than crawling through the attic) to install the ceiling support box -- and at the same time, use an extension on the support box to keep the insulation away rather than installing a separate insulation shield.

Do I have that correct?

Based on my measurements and probing through the living room ceiling it looks like I've got ~19" of height in the attic between the top of the drywall that makes up the living room ceiling and the bottom of the roof decking.

Just extend the support box up to the roof decking on the low side of the pitch and leave the rest open to the attic or cut the extension to follow the slope of the roof?

In either case, do I need to fab up a sheet metal "cover" for the top that would take the place of the storm collar that would top the normal insulation shield to keep crap out of there or is it just left open to the bottom of the roof flashing?

Thanks for the help! I'll run off and start another thread about the double-wall stovepipe questions!

You would extend the whole thing up to the roof deck leaving nothing open to the attic. You would then put your flashing and storm collar on as normal.

 

[GaryOR]

You would extend the whole thing up to the roof deck leaving nothing open to the attic. You would then put your flashing and storm collar on as normal.

I know I'm probably over-thinking this, but I tend to do that.

Should I cut the support box to match the roof pitch? Or just snip the corners with shears and bend down the excess to fold under the roof flashing?

 

[Ludlow]

Low pitch just tear off enough shingles and plywood and go in from above. Use a good tarp if you dont get it buttoned up in one day.

 

[webby3650]

To make sure I understand what you're both saying . . . . .

Cut the roof hole first, work through it (rather than crawling through the attic) to install the ceiling support box -- and at the same time, use an extension on the support box to keep the insulation away rather than installing a separate insulation shield.

Do I have that correct?

Based on my measurements and probing through the living room ceiling it looks like I've got ~19" of height in the attic between the top of the drywall that makes up the living room ceiling and the bottom of the roof decking.

Just extend the support box up to the roof decking on the low side of the pitch and leave the rest open to the attic or cut the extension to follow the slope of the roof?

In either case, do I need to fab up a sheet metal "cover" for the top that would take the place of the storm collar that would top the normal insulation shield to keep crap out of there or is it just left open to the bottom of the roof flashing?

Thanks for the help! I'll run off and start another thread about the double-wall stovepipe questions!

Cut the hole for the support box where you need it. Then I reach through that hole with a plumb bob and mark the Center line on the roof. I then cut my hole in the roof. I also don’t tear back a bunch of shingles... after a few hundred you tend to learn a few tricks

 

[webby3650]

I know I'm probably over-thinking this, but I tend to do that.

Should I cut the support box to match the roof pitch? Or just snip the corners with shears and bend down the excess to fold under the roof flashing?

Cut the box to match the roof pitch. Depending on the brand, the box may not be long enough, then you’d want to extend it with sheet metal.

 

[bholler]

Low pitch just tear off enough shingles and plywood and go in from above. Use a good tarp if you dont get it buttoned up in one day.

No need to go that far. I either do like webby said and start inside or locate the stove inside and drill straight up through then work from above.