Roof support, how often?

[tahoeacr]

I think I need to add another 3 feet to my stack. Question is how much support and where? The slope is not towards the chimney so 0 issues of ice/snow. I have a 4 foot piece that is attached at the eves. At the top of the 4 foot piece is a 3 foot piece. At this connection(top of the 4 foot piece) I made a 5 inch band attached with sheet metal screws. 1/2 inch supports go off of this down to the roof. This is a total of 7 feet past the roof line. I want to add another 3 feet to this. The total chimney above the roof would be 10 feet. The current chimney is rock solid. I grabbed on it when I was done to make sure that if I started to fall of the roof I would have a hand hold and not bring the chimney down on top of me. There are 80-120' trees all around so no large winds. I have never recorded any wind higher than 15 mph off of my back deck. I would like to add the 3 foot piece and leave it at that. Come spring let a pro add another roof support if needed.

This is the original set-up before I added another 2 feet. The two foot piece was added right below the 30's to move the top one right to the eve's. Current length is 17 feet from the "T" and 3.5 inside. Elevation is 6,536. I could add another picture of the current set-up if that helps.

 

[begreen]

What stove is this and why is it smoking? Partially seasoned wood or is this a start up fire picture? The reason I ask is I'm wondering about how cool the flue gases are.

There should be a brace for at least every 5 ft of pipe over the roof. Before investing in exterior pipe, how is stove connected? Is there more than one 90? Even if not, you might try replacing the 90 with a pair of 45s with a diagonal connector to improve draft. If the interior pipe is single wall, going to double wall will also help.

I would think 17ft would be enough. Have you checked for negative pressure in the area of the stove? Does draft and performance improve if a close by window is opened a bit?

 

[tahoeacr]

That's a start-up picture. Stove is a US Stove model 2007. Single wall was used inside up to the clearance code of the wall thimble. I used single wall to get an adjustable 90. I wanted to do two 45's but the offset wouldn't work out. 36" straight up to about an 80 degree. One foot straight pipe in to a 15 degree(double wall). Then it's a one foot straight thru the wall to the Tee outside. If I open the door next to the stove I don't get any smoke usually. If the flue temps are in the 500 range I am also good. Just hard to keep them that high. I do have pine that is not seasoned long enough. I bought a moisture meter and start the fire with kindling that's in the 12 -22% range. I don't put any of the un-seasoned stuff in until it's got a good base and really hot. The forestry went nuts this spring and cut down more trees than imagineable. All the wood is free to the taking and stacked on the ground already. Couldn't pass that up when it only takes 45 minutes to go fill up my long bed F350.
This thread has interior pics.
https://www.hearth.com/talk/threads/33081/

Thanks.

 

[begreen]

It sounds like the stove might benefit from an Outside Air Kit (OAK). If the house is tight there can be negative pressure in the house that is fighting the flue draft. This could be particularly bad when an exhaust fan, furnace, dryer or gas appliance is running. With your high altitude the draft can be touchy.