OT: Roof framing, alteration Options

[thomasotten]

I have an existing roof on my house that is pitched and creates a cathedral type ceiling underneath. I am considering increasing the pitch of this roof, for ascthetic reasons mostly, but also to add insulation to the roof, which I don't thick is adequetly insulated. There is no attic space right now, so I cant' be sure of the insulation, although it gets hot in summer time. I want the final roof to be 12/12, and to do this, I would need to raise the ridge by about 2'. From the ridge, I would then run rafters down to the bottom of the roof fascia. Instead of raising each rafter up and causing a mess, I am considering building a structure over the exsiting roof, and then sheathing over. That way I don't disturb the ceiling. I was thinking of also doing this in phases, keeping the existing shingles on as a I go. What do you think?

[JeffBowlsby]

A couple of things to consider:

that amount of work on the existing roof deck is going to pop existing sheetrock fasteners, so plan on patching, retexturing and painting the ceiling anyway.

The new roof cavity space needs to be ventilated above the insulation.

A couple small pilot holes through the existing ceiling may be able to confirm the existing insulation thickness. Easy to patch.

If you frame over the existing sheathing, creating a new cavity above the existing roof deck, the local code may require fireblocking in the newly created cavity.

You could leave on the existing shingles, but doing so may conceal decayed framing if there has been previous water intrusion and some areas of the shingles would need to be removed to install the new framing.

Also, adding new framing over the existing, changes the structural loads - it adds weight to the walls, roof beam and foundations...or is the exiting framing trusses?

You would need a permit, and an engineer or architect in your local jurisdiction to run calcs and coordinate structural and waterproofing details and connections.