[mindytop]

Hi DIYers! I have a framing question.
I am building partition walls in the second story of a rowhome with a "flat" (7-degree slope) roof. Previously there were three rooms upstairs, all with different ceiling heights. The front room had wooden joists that formed a flat ceiling at 9', the hallway had wooden beams suspended from the roof trusses at 8'6" high (perpendicular to the joists in the front room - idk why), and the back bedroom had a drop ceiling covering a sloped ceiling from ~9' high near the hallway wall to just under 8' at the back of the house. I have demo-ed the drop ceiling and want to borrow a little space from each of these rooms to add a small bathroom. However, I'm a little stumped about the best way to frame the bathroom ceiling.

I had thought to build all of the partition walls up to the existing ceiling in each room, then attach joists to the sides of the studs (like balloon framing) parallel to and at the same height as the old hallway ceiling joists. The small, awkwardly shaped space above would then be closed off from the finished space in each room. None of the involved walls are load bearing, and the largest joist span would be 5' 3". Does that seem reasonable? Legal? Any obvious flaws or complications I should keep in mind? Can I use 2x4s for the ceiling joists, or should it be larger boards?

Thanks in advance!

 

[carpdad]

As long as you're sure, 2x4 is good for spanning little over 5'.

 

[wallmaxx]

Why attach to the sides of studs? Now you will have to fire block inside each stud bay.
Any balloon framing will require fire blocking...not difficult, just cut tight and square.

I would install fireblocking in-wall about ¾" down from the bottom of the proposed ceiling joists, then nail a ledger and joist to that.
Makes the GWB work easier.

2x4 is fine in this application.

 

[Nealtw]

We do them just like the picture @wallmaxx posted , we just add a block between every other 2x4 for extra nails.

And don't skip the fire stop blocks.

 

[mindytop]

Wow, thanks for the replies, guys! And thanks for the heads-up about the fireblocking.

@wallmaxx "Why attach to the sides of studs? Now you will have to fire block inside each stud bay."

I guess the reason for the balloon-style framing is that the only other idea I had involved building the room to 8' and then building a variable-length cripple wall above it, which seemed like more work (especially since I didn't know about the fire-blocking). Is there an option C that I'm missing?

 

[carpdad]

Fiberglass, I think full stud width, or rockwool, 2", passed for fire blocks in nj. Every 8'. Any pipe or wire holes. You can ask your town fire inspector.

 

[wallmaxx]

Wow, thanks for the replies, guys! And thanks for the heads-up about the fireblocking.

@wallmaxx "Why attach to the sides of studs? Now you will have to fire block inside each stud bay."

I guess the reason for the balloon-style framing is that the only other idea I had involved building the room to 8' and then building a variable-length cripple wall above it, which seemed like more work (especially since I didn't know about the fire-blocking). Is there an option C that I'm missing?

Balloon framing (vertically and horizontally) were found to be death traps in a fire.
Dropped ceilings are always more work as you build and study them. I have no idea what you are dealing with without pictures.
Your words above describe whet you see and that might be incomplete.

Fire blocking was found to slow the spread of fire and keep it in the vertical wall cavities.
If you nail your joists to the side of each stud, now you will need to fire block at the ends or the joists to slow the spread of fire horizontally.
And with a dropped ceiling it becomes like when you add soffits over cabinets.
Extra pre-sheetrock where the soffits go up against the ceiling joists, etc.

This is the DIY fork in the decision road. Meet the codes (even if they seem odd) or build to what you think is enough.
You could take pictures and talk to your building permit office..........they are the only ones who really have a say in these things.

 

[Nealtw]

Wow, thanks for the replies, guys! And thanks for the heads-up about the fireblocking.

@wallmaxx "Why attach to the sides of studs? Now you will have to fire block inside each stud bay."

I guess the reason for the balloon-style framing is that the only other idea I had involved building the room to 8' and then building a variable-length cripple wall above it, which seemed like more work (especially since I didn't know about the fire-blocking). Is there an option C that I'm missing?

If you are building new walls, you can set the same ceiling on those walls, no need for the wall above, the ceiling will hold the wall in place.
The option for firestop is plywood up to the roof behind the 2x4.

 

[mindytop]

Thanks again everyone for the responses! We definitely want to do this right - we pulled a permit for the framing and it will be inspected. We're expecting to fail at least once but would like to get as close as we can.
I think we're going to build the partition walls to the same height as the former hallway ceiling, tied into the side wall of the building like @wallmaxx drew, and we'll use fire blocking like @Nealtw drew. The ceiling joists would then rest on top of the 8' wall on the other side, right? Also, I think we need something that connects to the ceiling above to attach drywall to, right?
I'll try to take some pictures when I go out there tomorrow. Thanks again for all the help.

 

[mindytop]

Here's a profile of the existing ceiling with the new wall under it. On the left and right you can see new partition walls whose height matches the height of the original ceiling in the middle of the room. Where I was standing is approximately where the door goes. The older stud on the right will be removed eventually, but we're leaving it in for now to protect the old wiring while we work.

Below is a picture of the left partition wall from the other side. The gap between the wall and the ceiling on this side is really small, probably about 3".

Below is a picture of the right partition wall with the more sizable gap at the top. There will also be a closet to the left of this wall, but it's not built yet. Notice how we attached this one to the wall in front of the brick? Poor planning on my part, we didn't have enough 10' boards.... does this seem okay?

Thanks again.