[BroadStBully]

I recently destroyed one of the walls of my bedroom by taking out all of the lath and plaster, so now it is essentially down to only exposed brick. I want to install a stud wall with insulation and drywall, but the adjacent walls and ceiling are also made of plaster. How should I attach the stud wall if I cannot nail it to anything on the ceiling? Or should I just continue to tear down all the walls of the room(and ceiling!) and start from scratch?

[rtw_travel]

You should be OK, but you might want to take down the plaster and lath for two reasons:
1) if it was in bad condition (you'll end up with one perfect wall, and the rest with cracked plaster); or
2) you wanted to do some re-wiring/ replumbing/ or wanted to just have the room look 'finished' rather than partly done.

If it was me, I'd never just do one wall of drywall when the others were plaster. You can take the lazy approach and install drywall directly over the plaster if you wish. It'll make the room a teenie bit smaller, and you'll have to extend the jamb on all doors and windows, and reinstall baseboard, but its easier and less messy than taking all the plaster down.

When you're putting your new wall up, there should be something that is holding the plaster and lath of the ceiling up in the corner where the ceiling hits the brick. It should either be a 2 x ? Ceiling joist, or it will be the end of the ceiling joists on ~16" centres depending on which way they run. Just nail your top plate into that - and I'd recommend using a nail gun or screws to avoid cracking the remaining plaster.

You should find the same on the walls on each side. There has to be something that the plaster and lath is nailed into... and you can nail your wall into that.

If you decide to leave the plaster, you can remove a bit of the plaster on the side wall or ceiling to check what you are nailing into - because the first ~4" of plaster will be covered by studs and drywall

[BroadStBully]

You should be OK, but you might want to take down the plaster and lath for two reasons:
1) if it was in bad condition (you'll end up with one perfect wall, and the rest with cracked plaster); or
2) you wanted to do some re-wiring/ replumbing/ or wanted to just have the room look 'finished' rather than partly done.

If it was me, I'd never just do one wall of drywall when the others were plaster. You can take the lazy approach and install drywall directly over the plaster if you wish. It'll make the room a teenie bit smaller, and you'll have to extend the jamb on all doors and windows, and reinstall baseboard, but its easier and less messy than taking all the plaster down.

When you're putting your new wall up, there should be something that is holding the plaster and lath of the ceiling up in the corner where the ceiling hits the brick. It should either be a 2 x ? ceiling joist, or it will be the end of the ceiling joists on ~16" centres depending on which way they run. Just nail your top plate into that - and I'd recommend using a nail gun or screws to avoid cracking the remaining plaster.

You should find the same on the walls on each side. There has to be something that the plaster and lath is nailed into... and you can nail your wall into that.

If you decide to leave the plaster, you can remove a bit of the plaster on the side wall or ceiling to check what you are nailing into - because the first ~4" of plaster will be covered by studs and drywall

Thank you for the advice, and more importantly a clear explanation. So now it's a matter of 1.) deciding to put in the extra time and effort to finish the entire room, and 2.) locating the ceiling joists in order to attach stud walls. However I still have one final question now: What if the ceiling joists run horizontally(parallel to the top plate) and there is no joist where the ceiling meets the brick?

[rtw_travel]

That's what I was trying to explain. There will always be something above the corner of the ceiling... because something has to hold the plaster and lath up in the corner. It will either be a joist running along the wall, or a bunch of joist running perpendicular to the wall. Either way, there'll definitely be something there to nail in to.

[BroadStBully]

Ok, thanks again it really does make sense; I was confused because the lath and plaster I took out was only held up to the wall with old 1X2's and I was afraid of finding the same in the ceiling...