Stove pipe venting

[Ryan August]

OK, putting in new evaporator and additon to sugar house to hold it. I am not sure how to run the stove pipe and do it relatively safely. I would like to go up directly thru the roof, all I have for roof is metal, no sheathing. I was hoping to run a single wall pipe up and out the roof. The local hammond lumber guy said they have no thimbles or the sort to complete this and keep things water tight. Said against code. OK i dont want to burn down my sap house. Any ideas other than going with double wall pipe. Also, I have 2x4, so looking at 8 feet of pipe. Any harm in going to 10+. Also, if I decide to go out the side which will include elbows and horizontal piping, is my 8 foot of pipe 8 feet of total distance traveled or total height. I am under the understanding to get good draft I am looking for stove length (4 ft) times 2. So 8 feet. Thanks for suggestions.
RYan

[bowhunter]

I don't have any suggestions for venting through the roof other than using a proper roof jack and jacketed pipe. You need 8 feet of vertical pipe minimum for good draft. Ten feet of stack height won't hurt anything. Also if you add elbows and go through the wall horizontally you probably should add about 1 foot of vertical pipe per elbow to recover the draft lost in the elbow. So if you use 2 elbows you should have 10 feet of vent stack in the vertical position to compensate for the elbows.

[maple flats]

I made my own pipe. It starts at the base stack and reduces to a 12" pipe. This single wall pipe goes thru the steel roof and I have a storm collar above the keep moisture out. Then I have 2 more layers of stove pipe suspended from below the ceiling joists (truss bottom cord) up to the roof. My 1st layer is 12" diameter. The second layer is 16" diameter with 2" spacers made of sheet metal holding the 2" clearance. Then the outer layer is 20" diameter, also with the 2" spacers. The 2 outer layers terminate against the bottom of the steel roof. My trusses are on 2' centers, but where I was going to run the stack I moved one truss over 6" so it is 30" and the next is 18". When I built this I was required to get an inspection from the fire dept. before I could use it. They liked how I designed and built it. You could just as easily make one with 1" spacers. A principle of heat blocking for stoves and stacks is when a non combustible is spaced out 1" on non combustible spacers the clearance needed is cut in half. I just found the 2" spacers easier to install. An un protected stack needs 36", cut in half=18" and cut in half again is 9". Then on the truss faces towards the stack I have another 1" spaced layer on the wood. 9"/2=4.5". Has worked well for 10 seasons.