Flat roof connection to existing hip roof

[SliceCity]

Hello,

I am looking for for a detailed shear connection between a new flat roof and an existing hip roof. The ceiling line for flat roof and the existing house is the same. The proposed flat roof is 2x12 and the existing hip roof is 2x8. Is it appropriate to trim the end of the existing rafter to allow 1.75” bearing for the exiting rafter and 1.75” for the 2x12 rafters and apply 2x12 blocking adjacent to the 2x8 blocking and provide LTP clips on both sides? What is the common for this type of addition. See attached picture. The blue is the EN for the sheathing onto the blocking and the LTP clips. Is 1.75” bearing acceptable for rafters?

Alternatively, will a 2x12 ledger board nailed to the existing 2x blocking with hangers for the 2x12 work? Is that more common practice for this application?

 

[JAE]

Can the new 2x12's simply extend in and lap beside the existing 2x8's? Avoids the messy field trimming and still allows both members to bear on (and shed lateral shear on) the existing double top plate.

 

[SliceCity]

yes that would be ideal but how do I maintain the edge nailing for the sheathing at two different elevations? I would not be able to edge nail the diaphragms if I extend the 2x12.

 

[JAE]

Here's one idea.
Not shown would be some clips between the 2x8 rafter/truss and the top plate as well.

For residential I can't believe the lateral shear is all that huge so a clip of the 2x8 to the plate should work - (vs. some type of direct sheathing nailing to blocking and such).

 

[SliceCity]

Thank you for providing the sketch. The only issue is see is the edge nailing for the existing roof diaphragm. You would need additional blocking no?

 

[JAE]

Depends on your situation and magnitude of shear I guess.
As I mentioned above, if the shear is minimal (as most residential homes are) in roof diaphragms, then the use of a clip to laterally fix the existing 2x8 might be adequate to take the shear from the top of the 2x8 nail down to the clip (via rollover resistance of the combined and lapped 2x8 and 2x12.

This isn't kosher engineering but residential "engineering" usually isn't.

That said, yes, technically, added blocking might have to be fitted between the rafters and nailed down to the top plate.