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?

[flippa]

Are those 2x4’s that you are proposing for the new roof rafters? As I understand your drawing, the bracing are going to distribute loads onto the existing 2x8 roof rafters, essentially making some type of truss. In order to properly tie the truss system together, the existing sheathing will have to be removed to tie the added truss components into the existing rafters, as you show with the plates connecting the vertical bracing into the rafters. Additional bracing will be required to deal with horizontal loads; we’re not just dealing with vertical loads on a roofing system.

Honestly, this will not be as easy to piece together as you may think. Renovating an existing structure is typically much more expensive than replacement; it will all be time consuming custom work, and man-hours are expensive and add up quickly. I am sure that there are a few contractors on here that can back me up on this. The shingles, sheathing & existing insulation will need to be removed before you start building your trusses. You may find problems with the existing roof or wall structures caused either by age, insect or water damage that will need to be dealt with when encountered.

What will all of this demolition & renovation work do to the interior finish? Kinda hard to say. I would bet my car that the interior will not escape this type of major renovation unscathed and will need to be refinished, possibly replaced! As has been stated above, at a minimum you will have cracking & screws popping thru the sheetrock. Sheetrock won’t deal with all the banging too well. Most likely the sheetrock will be severely damaged by the demolition & construction (think of what happens as all those little screws start to pull thru the sheetrock; all the weight being held by that many fewer fasteners), it might even pull away & drop.

You might want to evaluate the cost of the custom renovation vs. removal of the roof and replacing it with new trusses. Complete demo of the roof would go quick, and new trusses can be lifted in place & set within a day or two. Performing select demolition while protecting the interior and fabricating the custom trusses on the roof will take quite a bit more time. Give it some serious thought.

With the field built/modified truss that you are proposing, I will guarantee that your city/town will require engineered calculations and a stamp on your plans to ensure that this system will actually work before they will issue you a building permit. A design professional will have to inspect the existing structure, design (or at a minimum, back up your design with calculations) & certify that the proposed roofing system will meet the building code. Talk with the town building department & ask them what will be required.