Smoke Stack Question

[derzuckermann]

Greetings! This is my first post - 2013 was my first season, keeping up with local tradition, my and surrounding properties have been providing maple syrup for centuries so I've been told...
I used a box stove and a small 1x2 pan, which took almost 24 hours to turn 55 gallons of sap into syrup. I didn't want to do that again, so this upcoming season is a quantum leap for me. I am putting the finishing touches on a 12x16 pole building sap shack and have already purchased a 2x6 hybrid hobby pan from Smokey Lake Maple. I ordered an arch from the same, and hopefully it arrives soon...

My question for all of the experts is about the smoke stack. My roof trusses are four foot on center with perlins two foot on center. The roof is copper colored steel. What kind of pipe should I put through the roof? Do I need triple wall or is single wall ok? I am reading about the high stack temperatures and am worried about being too close to combustible wood. I can center the pipe to be between the trusses and the perlins.

Thanks for any advice!

[1arch]

I had a wood stove in the garage at one time and ran the stack through the steel, uninsulated sidewall with no adverse affect.

[Scribner's Mountain Maple]

I think I may be able to help. I am no expert, but did just put a new stack through my ridge.

With your trusses at 4' on center do as you said and line up the arch to land centered where you want it in the building. I would then insert a header on either side of the selected stack location. Creating a 4' box out of framing material around your stack. Then you can cut out the perlin in the box, install a roof boot and that part is done. You should get the boot first to make sure the 4' box will work. May want the headers at 3' to screw down boot.

To deal with the stack heat and combustible wood, I used heat shields on ceramic fencing insulators screwed into the wood surrounding the stack wherever it comes within a few ft of any wood. If you have no heat shield material, you can use roofing on insulators.

As for stack material, single wall stainless is what I recommend.

I hope this helps.

Ben

[lpakiz]

My rafters are 24 inches on center, meaning I have 22 1/2 between the wood rafter surfaces. I use 12 inch, single wall, SS pipe. This gives me 5+ inches from pipe to wood, with no sign of overheating. I did watch and check for heat pretty often the first few days. The roof jack is about 13 inches in diameter, giving a small space between the pipe and jack to creat a draft of cooler air exiting the room. I made metal spacers with 1/4 inch bolts and spacer nuts to center the pipe in the jack.
As others have said, a heat shield is easily constructed with sheet metal and spacers. If I could custom-build my roof jack, I would make it at least 25 1/2 inches wide, so I could fasten it to the rafters, and at least the same in the other dimension.
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[unc23win]

I did mine very similar to Scribner's I also have trusses on 4' centers actually ended up dead center under perlin so I had to cut it out. To get the headers which I cut about 52" in the right place I put 1 screw in each corner of the roof jack and the took them out so I could center the header under the holes and then put caulk under the jack and screwed it down. So all the wood is at least 2' away from the stack.

[derzuckermann]

Ok - this is all good information! I checked with the metal roof supplier that I used, and they have a roof boot that they sell, but it's only good to about 400 degrees. I think that's way too low. So, I found roof flashing for a 10" stove pipe at Northline express:

http://www.northlineexpress.com/chimney/chimney-pipe-stove-pipe/duravent-chimney-pipe/duratech-chimney-pipe/10-inch-duratech-chimney-pipe/10-duratech-0-12-6-12-adjustable-roof-flashing-99149-99149.html

I have installed these before, even on a metal roof, but it was ugly. I want this to look semi-good. How would you guys install a flat flashing against a metal roof that has ribs?

Thanks!

[maple flats]

Just run it thru as centered as possible using single wall pipe, then use fireproof insulation or layers of tin spaced 1" for each to protect the wood.
I have mine protected by home made triple wall from the bottom cord of my trusses to the roof. My stack is 12" and I made a 14" to go around it with 1" spacers of tin, then a 16" around that the same way. Each time you add a layer of tin, spaced 1" with open venting top and bottom, you cut the clearance needed in half. Thus if you need 3' clearance, 1 layer cuts that to 18", the second layer cuts it to 9" and if needed a third layer cuts it to 4.5". You will be fine for the trusses with just 1 layer,but you need more to protect the perlins, or use steel or structural tin in place of the wood for that portion of perlin.

[Michael Greer]

The stack temperatures can be quite high...higher than your wood-stove by far, and anything within a foot or so will eventually burn. It's very exciting when the roof catches fire while your distracted by syrup and you don't want to go there. An un-insulated pipe can be protected by surrounding it with a larger pipe...and plenty of airspace. Individual rafters or beams can be protected by wrapping them with sheet metal shields with air spacers behind,,,and plenty of clearance. Insulated pipe is expensive, but so is building a new sugarhouse.