L- shaped Addition... Roof Framing

[jaw22w]

We are planning an addition onto my son's house. The 28x24 addition will make his 30x36 house into an L, so the ridge lines are perpendicular to each other. After I set the first 13 trusses on the addition, I would have to frame the extension onto the existing roof.
I remember when I built my house in 1980, it had the same situation. The truss supplier sent succeeding smaller trusses to set at 2' centers to frame in this area. That truss system came all together.
I have been searching for some information on how to frame this area using a ridge board and rafters. Can't find anything. I'm not getting the terms right. What is this area called? It looks like the cricket I built behind my chimney.
I got the ridge beam and rafter part, but how does the rafter meet the existing roof deck?
I would appreciate if someone could tell me where I could find some information on building "big crickets".
This is going to be a weather sensitive project. Early in the project the siding will have to come off back to the house studs,and the overhang on the 14 involved existing trusses will have to be cut back. That lets us frame the floor and walls, and set trusses and deck before we need to start messing with the roofing in the cricket area. Can't let rain get in the house!
I know that some of you guys have run into the same problems in building additions. Anybody got any advice?

 

[zak77]

I just googled "roof framing L ranch" and got a video that shows what you're looking for.

 

[kwb]

What they did when we added on was trusses up to the original exterior wall. Then did exactly as you are asking about.
Peeled the roof off along the line that would become the valley in the roof.
2x8 (I think) was then put down on deck of old roof sheeting and nailed through to the trusses. Rafters were all individually cut, attached at ridge and valley and the framing was completed and sheeting applied. This made the house a "T". If you are doing an "L" I would think about if the roof lines are going to look right with the old gable end v. making that corner a hip style.


We were doing this in Late October/Early November so there was about a week or so with blue tarps between tearing into roof and the new roof going on. Had some healthy rains but no leaks through to living space.

 

[KenC]

What they did when we added on was trusses up to the original exterior wall. Then did exactly as you are asking about.
Peeled the roof off along the line that would become the valley in the roof.
2x8 (I think) was then put down on deck of old roof sheeting and nailed through to the trusses. Rafters were all individually cut, attached at ridge and valley and the framing was completed and sheeting applied. This made the house a "T". If you are doing an "L" I would think about if the roof lines are going to look right with the old gable end v. making that corner a hip style.


We were doing this in Late October/Early November so there was about a week or so with blue tarps between tearing into roof and the new roof going on. Had some healthy rains but no leaks through to living space.

I've done a few of these. The end of the new 'short' rafters that meet the old deck and 2x8 are cut with a bevel angle matching the old roof pitch ( I think a 4/12 matches a 20deg bevel for instance) and a reverse angle to the ridge cut.

 

[firebirdparts]

I've done a few of these. The end of the new 'short' rafters that meet the old deck and 2x8 are cut with a bevel angle matching the old roof pitch ( I think a 4/12 matches a 20deg bevel for instance) and a reverse angle to the ridge cut.

This right here. Cut to fit. It's fundamental.

Space your jack rafters so that they land on a structural element (rafter or truss) in the old house. If this messes up the spacing on the sheeting, just make it work. It'll be plenty strong.

Where your ridge beam runs in to the trusses, make an attachment there that suits you. You can run a whole rafter beside the truss if you want to.