Shack design questions- start with chimney

[mudr]

Hi guys. Looking at my shack design, probably the biggest thing I am scratching my head with is the chimney stack. Getting a 2x6 with 12 ft of 8 inch pipe, 2x length of the evap. When they say that, is it evap height+base stack+12 ft of pipe? Or is the base included in the 12 ft of length, so that it is evap eight plus 12 ft? Either way, it should be enough length to get to the roof of my shack. Planning on 10 ft walls, add on 4 ft to the center of the roof, I should be about 14 ft at the ridge. Also, looking to slighly offset the evaporator so that the roof flashing tucks up under the metal ridge cap.

Now the fun part: roof penetration, fire codes, and waterproofing. First off- my brother, the contractor who I will likely lean on to help me build, is an assistant fire chief. He will want this to be up to code, which is fine and what I want anyway. However, he has personally always stuck to triple wall pipe, I really don't know why. It started with his coal stove, maybe they need it, but he seems to think that triple wall is always better. To me, class A is class A. If I can get the same temp rating and distance to combustibles in a narrower pipe, that is a win, right? I will post a link below to two styles of Class A penetration kits. One has the full support box, which acts as a heat shield I think, while the other uses the support band, which uses the Class A chimney itself to provide the heat reduction. Is either way better? The second option is cheaper but would require me to use another section of pipe so it may be a wash.

Finally- corrugated metal roof flashing. Both kits offer a metal roof flashing option, but they look flat. How do they actually adhere to the roof and keep water out?


Support box style: https://www.northlineexpress.com/8-duratech-cathedral-ceiling-support-kit-dt820-kit-17084.html
Support band, using chimney pipe style: https://www.northlineexpress.com/8-duratech-roof-mount-support-kit-dt840-kit-17086.html

[OldManMaple]

The thing to remember with Metalbestos or Duratech or ANY factory built chimney listed to UL103HT is that these are residential type chimneys with 1000 degree F maximum output under normal operating conditions. They're tested to 2100 degrees F as in the event of a chimney fire, which is normally short in duration. If you are going to use factory built chimneys and run it higher than 1000 degrees F, the chimney pipe should be installed with more than the minimum 2-inch clearance to combustibles to be on the safe side (and then use the warranty card to light your first fire).

[Ryan Mahar]

I would recommend just installing the 2x6, once shack is built, and then add your existing stack on it. You undoubtedly will have to buy a few more pieces to complete the hieght you need. Trying to calculate the length needed now will just be a headache. Unless I am mis-reading you question? My design sounds like exactly what you are trying to do.....Regarding the stack and heat transfer, so long as you have adequate non-flammable material with some airspace between stack and the wood framing you will be fine. I have about an inch air space between rafters and then concrete board. Then about 4 inches between there and stack. Never had a problem. Not sure where you are in wny, but I am just over the VT border if you want to visit my shack to get some ideas. I visited many before we built ours............

[mudr]

I guess my main two questions were: Is one of those two roof penetration kit styles preferred to the other, and which (double vs triple) wall type do you guys prefer. Oh, and the follow up of how to put flashing down on a ribbed steel roof.

[Ryan Mahar]

Maybe it would be easier if I just took a picture of what I have. Of course in the great state of Vermont, we have NO codes so if the shack burns down it burns down. But honestly what I have is pretty good and far safer than other designs i have seen. I have only the SS smoke stack, into a SS roof jack and then up into the sky. The stack is about 8" from the cupola outside with nothing in between. My roof jack made by leader is just a flat piece of SS with the stack going from it of course. It sits right on top of the ribbed roofing. There are small pieces of foam filler that are designed to go under the roof jack on the edge to fill the gaps ( from the roofing supplier).....I thought being foam and running a stack temp of 1000 degrees they would melt, but in 4 years they have never changed form so I guess that works! THe top part of the roof jack I have flashing over from the roof cap (side mount jack)....

[red dorakeen]

Does anyone use an elbow from the arch into a masonry chimney?

[Michael Greer]

My rig has a 13" chimney, so metalbestos was not an option. I had a roof jack built with a 15" opening at the top, and tapering out to about 18". There are vent holes at the top, protected by the storm collar, wich let out the excess heat. I built my own triple wall with 16" and 18" galvanized pipe sections spaced around the inner one. I wondered how it would perform, and attached one of those magnetic chimney thermometers up near the roof. No matter how hot the flue, that outer pipe never goes above about 75 degrees.
Flashing over a ribbed roof is easy. Put the foam gaskets under the flashing out around the outer edge, and drill your screws through it into the ribs. No need to shape the flashing to the ribs, and the only reason for the foam is to prevent blowing snow from getting in there.

[MISugarDaddy]

I used a cathedral box and double wall pipe going through and extending out from the roof. To me, I would rather spend a little more and not have to worry about a fire, especially during syrup season. It might be better to let your brother over build it a little than to try to save a few dollars and be sorry later. Can't help you on the roof flashing question as I have a shingled roof.
Gary

[mudr]

Thanks guys. First, I didn't realize that the flashing had foam, interesting. Makes sense, as long as it holds up.

MIsugar- I will let my brother play a heavy roll in the design. I'm just trying to understand double vs triple. They appear to have the same ratings, with different outside diameters. Much if what I have come across online suggest going with double wall class a.

[maple flats]

The 12' includes the base stack, but you have other factors to keep in mind. A stack must be at least 3' above the roof penetration (at the high side) and must be 2' above the highest point within 10'. If you are having a cupola, that means it needs to be 2' higher than the peak on the cupola.
I made my first stack I had a 8" stack above the base stack, single wall pipe that went up thru the steel roof at the peak and then extended up to about 30" above the peak of the cupola roof. From about 1' below the ceiling cord on the trusses, up to the under side of the steel roof, I made my own triple wall pipe. It was suspended off the trusses and was made of an 11' and a 15" pipe, each spaced from the inner pipe with sheet metal spacers, pop riveted to hold the spacing. Every time a layer of tin is placed on a 1" non combustible spacer between the hot stack and the combustible surface the needed clearance is reduced to half, I used 1.5" spacers. Then the outer layer was spaced the same and both extended up to the underside of the steel roof. All of my other trusses were at 24" on center, except where the stack was, for that I made it 32" O.C. In my location, we must get inspected by the fire dept, they liked it extremely well and I had no problem getting the inspection certificate issued. After I got my new pans and bought new ss stacks I again built my own, but this time I put the 12" stack up, single wall, similar height as the smaller one had been, but I did the under part under the roof differently. This time I ordered 2" ceramic blanket (rated for 2300 F ). I wrapped it around the 12" pipe and tied it with wire to hole it in place so I could attach an outer layer of SS. I then made the outer layer out of 30 ga. SS, cut slits every inch around the bottom and bent them inward to touch the inner stack pipe and to give it a "finished" look. That outer layer is made so that it clamps around the insulation and it extends from 18" below the bottom of the trusses up to tight against the steel roofing. On top, I have a storm collar that fits the stack tight and extends out beyond the roof penetration, again, the fire dept liked it.
Having done both methods, I like the latter better, but both were effective, the second was neater.

[jimsudz]

My 12" stack goes through the peak of my shanty. I had a Amish gentleman make a 16" roof jack out of ss and a storm collar. I took a 15 gallon oil barrel,cut both end out and welded 4 tabs on which rest on the jack and under the storm collar. The stack has enough clearance,with air movement to keep the rafters cool. Without the barrel I have had my rafters smoldering.This is one place you don't want to skimp.

[mudr]

Hey guys, been a while since I started up this thread, been busy for a few weeks. I have a follow up on the shack build, figured I'd keep it in the same thread.

My wife and I want a pretty basic but well built pole shed with board and batten. We don't have plans to insulate or finish off. My aforementioned brother, a very good carpenter who also likes to go all-out on builds, is really trying to talk me in to insulating and finishing, in addition to going to a foundation/2-by framed structure rather than a pole barn. Does anyone here have a framed building for a shack? What are the benefits? I haven't talked to him much, I'm not sure he fully understands what we want yet.

Thoughts on pole vs framed?

[MISugarDaddy]

We went with a framed building for the same reason your brother is encouraging you to go to one, so we could finish it off on the inside. Not sure about New York, but when we had our initial inspection for getting our license, he stated that we would have to apply some type of coating to the treated posts we had used to support our feed tank. Instead, we just enclosed the area under the feed tank and use it for storage. We really like the finished walls because we can wash them if they get dirty. We also wanted to go with full footings (48" deep here) so we wouldn't have problems with the floor heaving from frost getting under it like it has done in our wood storage building which is pole type construction. We insulated the walls as well as the ceiling so we could heat it easily during the cold weather that we normally get during syrup season here in northern Michigan. I guess a lot depends on how you want it to look on the inside when you are done. It is a lot easier to finish the inside if you build it with studs and we like being able to keep all the rodents outside of our sugarhouse. There are pictures of our project in the link in my signature.
Gary

[anchorhd]

Take a look at this.

http://www.ongov.net/planning/documents/D.AgriculturalBuildings-DOS.pdf