Cutting Roof for Class A Today - Any Advice?

[tutu_sue]

Hi Guys, going to cut the roof today for installing 6" Class A (8" O.D.). Any tips, tricks or rule of thumb for cutting the opening with the 2" clearance? We have a 4.5/12 pitch. Want to get this right the first time. Going to rain tomorrow...thanks in advance!!

 

[WES999]

Here are some pics of how I did my install, I used a level held against the pipe to mark the roof for cutting. I had to go and enlarge the hole in a few places to get the 2" clearance.

Good luck.


https://www.hearth.com/econtent/index.php/forums/viewthread/28386/

https://www.hearth.com/econtent/index.php/forums/viewthread/28385/

 

[Brian VT]

The minimum cut would be a 12"W. x 12.82"L. oval.
I would just cut a 13" circle.

 

[Nic36]

I did almost the exact same thing Wes did. See his second picture link.

I probably went through more trouble that I needed to, but I cut the hole out in the roof just big enough for a section of chimney to fit through. I then placed the flashing over it, marked the edges of the flashing with tape, removed the flashing and section of chimney sticking out the roof. I then put the flashing back where the tape marks were and used a utility knife to cut along the inside edge of the shingles so my hole would be exact. I had to basically cut twice since my first hole wasn't big enough for proper clearance, but it was the exact place it needed to be, and I didn't cut it too big.

 

[Highbeam]

My installer set the flashing on the roof and then reached inside to mark the proper sized hole on the roof by tracing the inner oval. You should have drilled a pilot hole from inside the attic which is the centerpoint of the penetration. Center the flashing on that centerpoint.