I am assuming I can approach a roof opening for a chimney pipe installation as I would a skylight. I am up on the clearance and chimney requirements but I have to make room in the attic and roof to run it. This is Simpson Duravent 6" triple wall which has a 10" OD. The chimney will pass through the attic via the 14.5" support box but does not clear the ceiling joist and roof rafter above. This is a single story, corner installation from the den below, through the ceiling, about three feet of attic space and through the roof Can I just head these off and frame the opening as needed? Thanks, Jim.
You will likely need to talk to an engineer about this. I have seen roofing system that were designed as way overkill and would be safe to do this. I have also seen roofs that I wouldn't want to cut one board out for fear of a "widowmaker". It will also depend on where you live. If you live in a region that sees 4"+ snows a couple times a year, you need to take into consideration the snow load. Likewise with wind and rain. There is a lot of engineering goes into making a roof and sometimes can't be modified safely.