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NorthRick
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# Posted: 29 Oct 2023 11:24am
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I did a search both here and on google but my search prowess must be off as I couldn't find the answer I was looking for.
The cabin has a cathedral ceiling. Roof pitch is 8 in 12. The wood stove needs a 6" ID flue pipe.
What size opening do I need to block out in the insulation in order to have a 2" clearance from the piece that goes through the roof?
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Steve_S
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# Posted: 29 Oct 2023 11:59am - Edited by: Steve_S
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For GOODNESS SAKES DON'T !!!
You are Far Better off going out a Side Wall through T-Connector and a cleanout cap outside !
I went through my Cathedral Ceiling same pitch roof & 6" Insulated Pipe. The "BOX" requires 18"x18" clearance.
I used ONLY Selkirk Co parts as my chimney pieces are all from them. Learned LONG AGO not to mix different vendor pieces that hard & expensive way.
A Wall connection goes through a "Thimble" that does not need as much space and the benefits, especially cleanout & maintenance is a Huge WIN. I am actually considering pulling my current Through the Roof setup out and putting it through the wall, I've had enough of the circus. Getting too old to furtle around with that nightmare.
IF you are set to go through the roof, then make sure you install proper Ice/Snow deflectors and be certain you have the correct top "cone". some are vented, some not and it depends on the whole setup which is right for you in your location.
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gcrank1
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# Posted: 29 Oct 2023 01:30pm - Edited by: gcrank1
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My '83-'84 build had the support box and straight through the cath roof, it vented Great (may have been Selkirk?; was dbl wall SS). I put it near the ridge so never had snow-slide issues. The pipe and its weather collars never gave problems tho I did burn out the spark screen (made a replacement out of 'hardware cloth'.
Our current one came with a through the gable pipe also near the ridge, it drafted terrible. After the 1st winter we pulled it out (actually turned the opening into a summer vent) and put in an LP heater.
BUT, that pipe was NOT insulated which likely contributed to the poor drafting, along with the Tall pines close by on the west; the winds were too switchy even with the stack well above and beyond the specs.
It is recommended that if you must go 'thru a wall' that you use a 45* elbow off the stove with an angled pipe to another 45* at the thimble to not slow the air flow too much.
I was looking at the straight up pipe again, tho I hated the thought of going thru my good metal roof. That was 3? years ago and the Min. $600 of pipe and all has certainly gone up. I decided I could buy a lot of LP for that and Not go thru my roof (and there were no guarrantees that I still wouldnt have draft issues).
No regrets yet, ymmv.
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ICC
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# Posted: 29 Oct 2023 01:59pm - Edited by: ICC
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Steve, are you sure it was 18x18? The ceiling supports I remember would fit between a pair of 16"OC rafters or ceiling joists.
I have no reservations about penetrating a roof when properly flashed. For a metal roof the high temperature silicone boots cannot be beat
On my roofs I installed metal step bars up to the chimney from the eve. However, that said I reached a point in my life where I do not want to scale a pitched roof anymore. I'll either utilize a younger family volunteer or hire that out. But I have not been using the wood burner regularly since I installed thr heat pump that runs off solar.
Some wood stoves are made with a user changeable chimney pipe exit. Those seem to work okay for a draft when the outside vertical run is long enough. Check with the stove manufacturer if going out the wall.
A good cleanout at the exterior tee can be very nice to use.
-Izzy
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ICC
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# Posted: 29 Oct 2023 02:02pm
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https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.selkirk corp.com/literature/S9_Cathedral_Support_Box_%2528SB%2529.pdf&ved=2ahUKEwjjl-_25puCAx UOKEQIHV51Dh0QFnoECBEQAQ&usg=AOvVaw0SnuJVDUhXIY9IkuGS48G_
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Steve_S
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# Posted: 29 Oct 2023 03:25pm
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I measured the box to verify before I posted, this one is 18x18 square. Can't tell you the depth though. When we installed it we have to make changes as my rafters are 24oc. It is a few years old so things likely did change. I believe they had a couple of different models but again that was a few years back.
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gcrank1
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# Posted: 29 Oct 2023 03:42pm - Edited by: gcrank1
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I had to go through the loft floor first so that got the support box; it was the dbl wall insul 6" pipe, iirc it had to be x distance from combustables (wall) and the box was made to go between 16"ctr joists.
I also had to make sure that pipe to wall distance accomodated the stove placement below for its proper clearances.
Then it had to go between the roof rafters, 24"ctrs without compromising and come out near my ridge.
Gotta say there was a LOT of measuring and re-measuring! And nervousness drilling the 1st hole in the roof.
A laser level would have been handy....I had a plumb bob. It all worked out fine.
The support box and roof piece had clear specs and the s-box located the pipe clearance to the joists. For the roof opening I think it prudent to start smaller than you think, you can always make the hole bigger.
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ICC
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# Posted: 29 Oct 2023 05:46pm - Edited by: ICC
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Quoting: ICC But I have not been using the wood burner regularly since I installed thr heat pump that runs off solar.
That is at home. Here at the cabin it's either wood or propane (DV wall heater). Chilly today so I am doing an afternoon wood warm up. That is a Vermont Castings Aspen. Incidentally the T&G behind the stove is Aspen, from a tree of ours I harvested and milled almost 20 years ago. No stain, just water carrier clearcoat.
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gcrank1
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# Posted: 29 Oct 2023 07:18pm
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Rick, what insul pipe system are you using?
Each brand has its own specs, instructions, support and firestop parts afaik; should be able to look it all up online. The illustrations were invaluable.
When I was considering doing a system I ended up as a visiter on a couple of wood stove fora, all kinds of info was readily available there, so much I didnt find the need to join to make my inquiry.
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Brettny
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# Posted: 30 Oct 2023 06:47am
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Quoting: Steve_S or GOODNESS SAKES DON'T !!! You are Far Better off going out a Side Wall through T-Connector and a cleanout cap outside ! I went through my Cathedral Ceiling same pitch roof & 6" Insulated Pipe. The "BOX" requires 18"x18" clearance
No your not. Heat rises. And no it dosnt. I just put one 6in ceiling box in this weekend that required a 12.25in square.
North Rick. You really need to pick what chimney brand your going to use and read the directions. Clearance to combustibles are important and so is installing a chi.ney correctly.
I have installed 4 through the roof chimneys to date. 2 in shingled roofs and 2 in metal roofs. None leak and all 4 drafted like the Dickens and dont build up creosote. My parents had a through the wall chimney and it wouldnt draft for crap and would build up creosote about 4x faster.
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Aklogcabin
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# Posted: 30 Oct 2023 09:56am
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Great morning N R. Better through the roof. I built a roof ladder to get up to our cabin chimney. Dan the fireplace man has everything that you need. And you won't end up not having the right stuff. I went with the double wall stainless. Expensive but one n done. Don't remember the support box being 24x24. Probably closer to 16". I can measure one of the 2 boxes we installed for our new house if you need.
I kinda like the silicone rubber boots. They seal up tight against the pipe. 2" clearance around pipes. So you end up with a 10" iirc hole in the roof.
Lakes are frozen over, small creeks should be soon just need some snow now. And it's cabin season again.
How is your build going ?
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NorthRick
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# Posted: 31 Oct 2023 04:41pm
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Quoting: Steve_S For GOODNESS SAKES DON'T !!! You are Far Better off going out a Side Wall through T-Connector and a cleanout cap outside !
Sorry, it is going straight up inside the cabin and exiting the roof near the ridge beam. Steel roof. My cabin neighbor has this set up and is able to clean the chimney from the inside of the cabin.
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NorthRick
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# Posted: 31 Oct 2023 04:47pm
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Quoting: Brettny North Rick. You really need to pick what chimney brand your going to use and read the directions. Clearance to combustibles are important and so is installing a chi.ney correctly.
I'm coming to this realization. I know what stove I want, a Blaze King Sirocco 30, but I'm a ways out on buying one. However, the roof is going on now and I need to make allowances for the eventual flue penetration.
Seems like things in the flue world are like the sign in the plumbing supply house I go to - Nothing in Plumbing is Standard.
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gcrank1
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# Posted: 31 Oct 2023 07:25pm
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I think the stove clearance stuff to combustibles is standardized; check your stoves of pref online and if anything err on the wide side.
That helps establish your stove footprint location to get the pipe support and roof hole.
Fwiw, I was pretty shocked to find out just how much square footage a wood stove takes up in a small place!
And the cabin world indoors revolves around the stove.
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Brettny
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# Posted: 31 Oct 2023 10:00pm
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NR. Why do you need to figure out the chimney now just because the roof is going on?
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Aklogcabin
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# Posted: 1 Nov 2023 11:35am
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The support box I have is 14"×14"×24" tall. Manufacturer and code suggest 2" clearance around combustibles for the pipe. A 6" id insulated pipe is 8" diameter outside. So a 12" hole. Only place I could find a silicone boot was spenards n Dan fire place man. If you are using the support box it already blocks the insulation from the pipe. Box has to extend min 2" below the finish cieling. You have 24" in hight to work with. So it would already be boxed in.
Just screw the box to a roof joist n add in the rest of the blocking for sheetrock. I can take a picture of mine if you want. How is your build going. You been out there lately
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NorthRick
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# Posted: 2 Nov 2023 01:04pm
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Quoting: Brettny NR. Why do you need to figure out the chimney now just because the roof is going on?
The roof consist of exposed (to the interior) timber rafters 4 ft on center. Over those is a 2"x6" T&G decking. Water and ice shield on the outside over the T&G deck. Then 8" thick foam insulation. Plywood sheathing over that, then felt, then steel.
I need to know where and how big of a hole to leave in the insulation that will be sandwiched between the T&G and the plywood/steel.
Interior roof
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Exterioir roof
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Brettny
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# Posted: 2 Nov 2023 03:34pm
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I would run the ceiling support box right up through the tongue and grove. It could be done later. You should prob trim around the box to keep the enda of the Tongue and grove together and help support the box.
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gcrank1
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# Posted: 3 Nov 2023 10:17am
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I SOoo like what yer doin!
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snobdds
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# Posted: 3 Nov 2023 04:59pm
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Up to a 8" flue pipe should be able to fit between a 14.5 inch rafter bay with 2 inches of space all around.
A general rule is class A pipe is 2 inches more than the diameter it's venting. So a 6 inch pipe is 8 inches in class A. A 8 inch class A is 10 inches, which will mean a 14 inch rafter cavity will be the maximum to also have a 2 inch air gap.
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