Redoing most of our roof.  Sistered rafters, new decking, bituthene and paper (Gabe and Piffin – decided to use paper over the bit, for the layout lines as much as anything else), going with Fantech fans to vent baths and laundry out gables and away from the soffit inlets.  Have a plumber coming by to double check my stack vent size for a new bath, and I’ll be asking him the following questions too.

We currently have a gas hot water heater and wall furnace near the middle of the house (1963 single story ranch).  We will probably be moving the HW heater to the attached garage next spring.  I plan on putting in a new exhaust vent over the garage, running the nearest appliance to this vent (maintaining 1/4 in 12 slope and getting a firewall flange), then running the next appliance to the remaining vent.

Here’s my main question.  I got one of those Taunton Code Check things at HD.  Pretty clear about distance from combustibles for single wall venting, but what about double wall?  My helper used to install wood stoves, and he said they had to be two inches away including cutting the hole in the roof two inches bigger than the vent.  Is this a UBC requirement or his old job’s practice?

A related question, any online illustrations for installing the roof jacks?  Everything I’ve read says bottom flange over shingle, top below, but more than one person has said to nail to the deck on a (basically) new construction scenario.

And the final, semirelated, question, if I sheet rock the garage ceiling with the right stuff, do I still need a fire wall between the garage attic and the house attic?  How about if there is a drop-down stair installed?

Thanks for any help. 

– Curtis