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?

[thomasotten]

Well, I talked about it with a contractor friend. I was asking him mostly about the loads and if this is a doable project considering the added weight. He said that sheathing over an existing roof is a common practice, mostly they remove the old shingles, and put new sheathing down on top of the old sheathing. Saves time and money. The only difference here is that I would be building a small truss on top and then sheathing over that. I mean I could pull up the existing sheathing, and build the trusses to the existing rafters, and then I would only have the weight of one layer of sheathing. So then the only real added weight would be the new pitched up rafters.