Vaulted Ceiling trusses 12" on center

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Buckholz

New Member
Mar 7, 2010
4
Flagstaff, AZ
Well, the new stove (Drolet Myriad) is here. I roughly located it where I want it to go, got up on the ladder to use the studsensor to fin out exactly where to locate my 14.5" x 14.5" DuraVent Ceiling support box. Dangit, discovered that my rafters/trusses are only 12" on center.

Suggestions? Thanks in advance for your answers. I have been lurking here for a coupla years while deciding how to wean off of natural gas forced air heating.
 

EKLawton

Member
Oct 18, 2009
130
central pa
I can see no reason for 12 o/c in your area. There must be something in that spot try a few feet in either direction..
 

John_M

Minister of Fire
Dec 10, 2008
614
Central NY
buckholz, It appears your house has a very strong roof. That's good. In terms of the ceiling support box, first try EK's suggestion. If all the trusses are on 12" centers, perhaps you can modify one to get the necessary clearances for the chimney. If modification is the only choice you have, be certain to have an engineer or architect design the modification so roof strength is not compromised. Then, if you or a friend are familiar with framing techniques, you can make the modification to the enginer's specifications.

Doing this job properly at the outset will give you many years of comfort enjoying the new stove and knowing the roof is as strong as originally built. Good luck. John_M
 

LLigetfa

Minister of Fire
Nov 9, 2008
7,360
NW Ontario
Then you cut one and box it in. I don't really see that as a problem. In fact it gives you more wiggle room.
 

John_M

Minister of Fire
Dec 10, 2008
614
Central NY
Blimp, If the trusses at Buck's house are 12" O/C, there are 10.5" between them, assuming they are of 2X material. He needs 14.5" between the trusses to mount the ceiling support box. I am assuming his new stove has an 8" chimney with 1" of insulation all around, making it 10" diameter. You are right about the required 2" of clearance around the chimney. So, add that to the 10" diameter and you have need for 14" of space. LLigetfa is right-cut one truss and frame-in the ceiling support box. However, I would suggest engineering approval before modifying a roof truss. Best wishes to all, John_M
 

Dakotas Dad

Minister of Fire
Mar 19, 2009
1,504
Central Kentucky
EKLawton said:
I can see no reason for 12 o/c in your area. There must be something in that spot try a few feet in either direction..

Actually, out there it's VERY common, because MANY people build with, or change to a terracotta roof, and they are heavy.
 

glassmanjpf

Member
Apr 4, 2006
226
Long Island, NY
Follow the advice given to have an Engineer provide the details for the modification. Truses are not like rafters.
 

elmoleaf

Feeling the Heat
Dec 11, 2007
432
Southeastern Massachusetts
Is this a cathedral ceiling with no attic access where you can look inside at roof structure?

If your ceiling is gypsum board, it's likely attached to 1x wood furring that runs perpendicular to the roof structure. Your stud sensor may be picking up attachment points to the furring, not the actual roof structure/rafter or truss locations.

Try poking an exploratory hole in the ceiling at your proposed pipe location and shine a light in there to see the actual roof structure and rafter spacing.
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,798
South Puget Sound, WA
Buckholz said:
Well, the new stove (Drolet Myriad) is here. I roughly located it where I want it to go, got up on the ladder to use the studsensor to fin out exactly where to locate my 14.5" x 14.5" DuraVent Ceiling support box. Dangit, discovered that my rafters/trusses are only 12" on center.

Suggestions? Thanks in advance for your answers. I have been lurking here for a coupla years while deciding how to wean off of natural gas forced air heating.

Not that it help with joists 12" OC, but the Duravent ceiling support box for 6" pipe should be 12"x12". 8" duravent has the 14.25" x14.25" box.
 

Dakotas Dad

Minister of Fire
Mar 19, 2009
1,504
Central Kentucky
BeGreen said:
Buckholz said:
Well, the new stove (Drolet Myriad) is here. I roughly located it where I want it to go, got up on the ladder to use the studsensor to fin out exactly where to locate my 14.5" x 14.5" DuraVent Ceiling support box. Dangit, discovered that my rafters/trusses are only 12" on center.

Suggestions? Thanks in advance for your answers. I have been lurking here for a coupla years while deciding how to wean off of natural gas forced air heating.

Not that it help with joists 12" OC, but the Duravent ceiling support box for 6" pipe should be 12"x12". 8" duravent has the 14.25" x14.25" box.

I just installed one, and the 6" ceiling support box for cathederal ceilings is definatly 14.25" x 14.25".
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,798
South Puget Sound, WA
Perhaps we are talking about a different part? I just remeasured the one I put in last fall and it's 12" on a side.
 

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gasavage

Member
Nov 21, 2005
109
Lafayette, Indiana

begreen

Mooderator
Staff member
Nov 18, 2005
92,798
South Puget Sound, WA
Nice find, it looks like that should work. Seems I need to update my Duratech file.
 

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Dakotas Dad

Minister of Fire
Mar 19, 2009
1,504
Central Kentucky
maybe there is a difference in the box based on DuraTech vs DuraPlus? My chimney system is all DuraPlus.

In fact that appears to be the case.. my DuraPlus instructions show all sizes of pipe get framed for the ceiling box 14.5" x 14.5", no matter pipe size. I would not have expected the box design to be different.
 

John_M

Minister of Fire
Dec 10, 2008
614
Central NY
Last fall I installed the same ceiling support box as BeGreen. Mine also measures 12"x12". Gasavage provided a good link but Simpson's info therein is confusing to me. I didn't search all the way through the Duravent/Duratech catlog but it seems to me that the Reduced Clearance Ceiling Support Box is intended to be used with a chimney meeting only the UL103 but not the UL103HT specifications and that is why it carries a "Reduced Clearance" approval. I will readily accept clarification or correction to my current interpretation. John_M
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,798
South Puget Sound, WA
Dakotas Dad said:
maybe there is a difference in the box based on DuraTech vs DuraPlus? My chimney system is all DuraPlus.

In fact that appears to be the case.. my DuraPlus instructions show all sizes of pipe get framed for the ceiling box 14.5" x 14.5", no matter pipe size. I would not have expected the box design to be different.

Yup, that explains it. DuraPlus triple wall uses a bigger support box. Thanks for the updated info.
 

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John_M

Minister of Fire
Dec 10, 2008
614
Central NY
buckholz, Welcome to hearth.com. Learn a lot and give a lot. That is what makes this an enjoyable and informative (and sometimes entertaining) site. I hope our initial confusion over dimensions, etc. has been clarified and helped you with a decision on your original post.

Please let us know how you plan to proceed with the installation and how it turns out. There is a saying here that "...it didn't happen if there are no photos". So, post an occasional photo as your work proceeds. You'd be surprised how many others really do care and want to learn from your experience. Good luck, best wishes, good health, and welcome. John_M
 

Buckholz

New Member
Mar 7, 2010
4
Flagstaff, AZ
Super responses folks.

Sorry, been prepping the floor for fresh tile, prepping the door for a new exterior door.

So, I live in Flagstaff at about 7,000' elevation. We are over 10 feet of snow for the year, more coming down.

Confirmed that I am 12" on center, found the original plans.

Funny thing is I am a mechanical engineer. Long on math skills, short on practical house construction skills, but dang good on engines....

I do have a cathedral ceiling, and the shingles are only about 8" above the penetration in my ceiling.


I am planning on yanking some drywall, and sister studding the 2x6" studs/rafters on each side of the the stud I plan to cut.
My main question is how long should the sister studs go. The span from the wall to the outside of my cathedral ceiling is approx 20'.

Once I sister stud, then I make a cut in the one stud and frame up a box to accomodate the chimney support box.


Sound like a good plan? Suggestions?

Oh ya, headed off on a business trip/scuba fun for the next week and a half in the florida keys, so will be focusing on having the door and floor prepped, so the tile guys can bust out that project next week. When I get back on March 21st, I will takle some electrical and cable rework behind the proposed corner hearth, and if the weather cooperates, will sister stud up the ceiling and make the roof penetration towards the end of march/early april
 

btuser

Minister of Fire
Jan 15, 2009
2,069
Principality of Pontinha
Eeeeehhhhh, sorry, but cutting trusses makes me queasy. Sissior trusses ( cathedral ceiling) are push/pull and really need some thought when you modify.
 

begreen

Mooderator
Staff member
Nov 18, 2005
92,798
South Puget Sound, WA
BLIMP said:
The class A chimney requires 2" clearance. I don't understand why the support box would require more.

6"r + 1" insul = 8"diam +2" NESW = 12" min. box dimenz. 12"OC joists = 10.5" clear 4 box.
 

gasavage

Member
Nov 21, 2005
109
Lafayette, Indiana
I'm using the ICC Ecxel stuff in my house, and using the Duravent Duratech stuff in my pole barn. Both are 6" with a 10" square ceiling support. Both are great products, with the Excel being a little higher quality & better fitment. The Excel is a little more $. If you're into exterior looks, the Excel also has stainless flashings & collars.
 
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