making converted attic into full height (roof tear off)

Question

Bought a house 5 years ago. Brick construction, single story with full basement (concrete walls). The attic was converted to living space (with permit) before I bought it, but it has 43-inch knee walls and only 6 ft headroom for about 8 feet of width. Virtually no closet space

the fact it was converted with permit presumably means that the foundations are strong enough to support true second floor. Was going to dormer it entire length, but exterior material costs are only about $5K more to replace roof and build 8 foot walls all round. So it seems like a no-brainer. I built my own 22 x 24ft garage with truss roof (had to register as GC to get permits), so it's pretty much same thing but 40-foot long and 12 feet higher :-)

Anyway, I know the architect/structural engineer will provide all this detail, but that's gonna take some time, so would like to get an idea sooner about 2 things I'm puzzled about.

1. The trusses need to be 24-inch on center. When i built garage I put extra studs under truss locations to carry load to slab. I'm not opening up first floor walls, so should I just space trusses at 16-inch so they are over the studs?
2. Normally, in 2-story framing, the floor joists for 2nd floor are square at the ends like diagram below. But as my roof goes all the way to the floor level on second floor (and it's 12/12 pitch), the joists are cut at 45-degrees.

So how would I support the new 2nd floor walls?

Can I just put blocking between the joists that gives me a continuous area (except the 45-degree cutout) for the new bottom plate

Can cut a 90-degree notch wide enough for a 2x4 bottom plate?

Can I offset the new studs by to be next to the joist?. Or can I bring the 2nd floor wall in a little? (load would be cantilevered). Have 3/5 inches to make up

Thanks Mark

Answer 1

There are lots of questions, I'm not sure if I got them all

1: your first level studs will be fine. It's good practice to align joists and 2nd level studs over the first level but is usually not necessary

2: There will be block that will need to be installed between the floor joists and the floor sheathing will be nailed over that. This is installed for several reasons including for a load path between the floors for the lateral forces, and to stop the joists from 'rolling' over. There is no requirement that the blocking be at the exterior face of the wall, and in this case I would put it at the interior face so that more of the floor joist depth is engaged to resist the rolling

3: there should be no cutting to fit the bottom plate. The second level sheathing is placed over the joists and blocking to the exterior face of the exterior wall studs. Your wall is built in this 'deck' just as your first level walls

Other items to consider:

1. you might have height restrictions which will not allow you to do this remodel
2. you will need to decide how to deal with the new upper walls and the brick below. Brick is heavy, and while your foundation may be adequate for the upper level, it might not be for another level of brick
3. For a change such as this, there will be a requirement to bring your lateral system up to code. This may, and is likely, to require work in the first level walls. Which means, opening them up...