Stack

[hitnspit]

Does the stack have to go straight up through the roof or can it go up 6 or so feet and then take a 45 or 90 degree outside and then up past the peak?

[maple flats]

It should go straight up, any bend causes an unwanted restriction. It is especially bad to go up a ways, then elbow to a horizontal, out thru the wall, then another elbow to vertical again and up, that is asking for trouble, to a slightly lesser extent, but still trouble is to go the route of vertical then elbow to a sloping upward angle, out the wall and another elbow to vertical again. By far best to exit straight up.

[Michael Greer]

I agree. A straight stack bears it weight straight down and needs little support to stay in place. It also means that ash and dust either fly straight out or fall straight down, leaving the stack always completely clear. Bite the bullet and cut that hole.