Roof Framing For Cathedral Ceiling

[flynztone]

Hi all I am new here so please be patient with me. I have a home in mid-Michigan in which I am adding a 20'x16' sunroom off the back. The existing structure has a gable roof pitch of 6in12. I want the addition to have the same pitch and also want to add right angled tinted glass to the gable end of the addition which is going to require me to have a cathedral ceiling. I have checked into scissor trusses and can only obtain a pitch of 3in12 under the 6in12 pitch which is unsuitable for my situation so I have made up my mind to install cut rafters.

My question is:
Do I need to install some kind of post/beam under the ridge board at the gable end or will a 2"x12" ridge board with 2"x10" rafters suffice? I can tie the existing structure end of the ridge board into the existing structure and also nail a rafter pair to the existing structure.

The addition is going to have many windows as well as a skylight so I am concerned about the side walls etc. having enough support for the roof and there can be no ceiling joists. Let me also add that the foundation will be 8"x8"x16" block layed up over a 42" footing.

Any professional advice would be highly appreciated.

Thank you

[Cole]

Are you talking about adding a stud underneath your new gable roof at the end of the ridge?

If so, yes you will need one. The roof will not hold itself up, it will eventually sag.

[tooltroll]

Ok, I'm assuming the ridge board is 16' long, running down the middle, and the rafters will span the 10' on either side, so your rafters will be a touch over 11' + whatever overhang you want.

If you need to worry about a snow load, you might want to double up the ridge board or use an LVL. I think the 2x10's might be adequate, but are you putting them on 12", 16" or 24" [ewww...] centres? Have you checked your local code requirements?

Either way, I'd put a double stud at BOTH ends of the ridge board, recessing the ridge board into the existing wall, if possible- the existing wall may not be as strong as you think!

But then, I overdo everything...

[Sweep]

You don't say where you live so I don't know what the roof loading is. Where I live (I'm not telling) you could get away with 2x8 rafters but that would not allow enough insulation to meet the code. The ridge beam is mandatory since you have no ties between the bottoms of the rafters. Where I live you would need at least two 1 3/4 x 11 7/8 LVL's with a fiber stress of 3,000 psi and a Mod of Elast. of 2,000,000 psi. They should be supported on 4x4 posts instead of 2x4's all the way to a foundation that can take the load. Where I live you would be required to show an engineer's stamp on the design to get a building permit. TrussJoist MacMillan will give you a stamped layout through your lumberyard if you live in the US or Canada.

[giddonah]

Where I live (I'm not telling)
I'm going to guess it's somewhere in the North East. Massachusetts maybe? :wink:

[Cole]

lol.