Room Within A Room Framing Detail

[Matt C.]

I'm planning building a room within a room in my garage (resting on the concrete slab but otherwise completely isolated from the existing outer structure), and I'm hoping someone here can answer a question about framing the ceiling joists.

Let's just say I'm building typical 2x4 lumber framed walls with 2x8 ceiling joists resting on the top plate. My understanding/assumption is that there is a rim joist on top of the top plate, running along the entire outer edge. Is this attached to the top plate by face nailing it from below? And are the ceiling joists themselves just toe nailed into the rim joist and top plate? Or it is standard practice to use joist hangers?

It also looked like some others were constructing stuff like this without a rim joist at all, but then it's even less clear to me how the ceiling joists are attached in a remotely stable way. Any tips? or detailed diagrams you can point me too?

Thanks!

[famadorian]

Not sure what you mean.

You're asking if you attach the ceiling joists of the inner room to the ceiling of the enclosing room?

If you build a room inside a room, can't you just build a steel cage inside it?

[Soundman2020]

Let's just say I'm building typical 2x4 lumber framed walls with 2x8 ceiling joists resting on the top plate. My understanding/assumption is that there is a rim joist on top of the top plate, running along the entire outer edge. Is this attached to the top plate by face nailing it from below? And are the ceiling joists themselves just toe nailed into the rim joist and top plate? Or it is standard practice to use joist hangers?

It all depends on HOW you are doing the ceiling. There are several different methods. If you are doing a modular inside-out ceiling, for example, that's a lot more complex than if you are doing a conventionally framed ceiling. There are pros and cons for each.

It would help if you were to post a detailed sketch or model of what you are planning, so we can give you more intelligent advice.


- Stuart -

[Soundman2020]

You're asking if you attach the ceiling joists of the inner room to the ceiling of the enclosing room?

No. He's asking about the entire ceiling framing concept for the inner-leaf framing, and how to do the part where the inner-leaf ceiling framing meets the inner-leaf wall framing. An inside-out ceiling could not be done the way you show in your photo.

If you build a room inside a room, can't you just build a steel cage inside it?

Why? For what purpose would you want a steel cage inside your inner-leaf room?


- Stuart -

[famadorian]

Why? For what purpose would you want a steel cage inside your inner-leaf room?

Isn't that the easiest way to do it, to create a room within a room, by just resting a steel cage on rubber, then use that cage to create the inner walls and ceiling?

[Soundman2020]

Isn't that the easiest way to do it, to create a room within a room, by just resting a steel cage on rubber, then use that cage to create the inner walls and ceiling?

No, that's not how studios are built. How would you attach your inner-leaf sheathing to a steel cage? Drywall nails don't go into steel very well.

The photo you posted is of a steel frame designed for creating an clean-room using glass or poly-carbonate panels that would be bonded onto the steel cage frame. Not much use for home recording studios.

The inner leaf of a home recording studio is usually wood framed, with sheathing nailed or screwed onto that framing. No rubber feet are needed.

Also, please read the forum rules for posting (click here). You are still missing something!

- Stuart -

[famadorian]

Isn't that the easiest way to do it, to create a room within a room, by just resting a steel cage on rubber, then use that cage to create the inner walls and ceiling?

No, that's not how studios are built. How would you attach your inner-leaf sheathing to a steel cage? Drywall nails don't go into steel very well.

The photo you posted is of a steel frame designed for creating an clean-room using glass or poly-carbonate panels that would be bonded onto the steel cage frame. Not much use for home recording studios.

The inner leaf of a home recording studio is usually wood framed, with sheathing nailed or screwed onto that framing. No rubber feet are needed.

Also, please read the forum rules for posting (click here). You are still missing something!

- Stuart -

Ok, I assumed to mean the location;) Done

Also, a rigid steel frame offers more mass than wood, so why wouldn't this be used? Fermacell steel studs would attach to this steel frame, then plasterboard attach easily to the fermacell steel studs?

[famadorian]

Please answer this, cause that's my current understanding. To build a room inside a room, it's better to use steel studs to construct a rigid steel cage that rests on dampers, like rubber or even shock absorbers. Is this not correct?

[Gregwor]

Also, a rigid steel frame offers more mass than wood, so why wouldn't this be used?

The stud's mass does not really matter. The sheathing mass is what matters. The framing strength matters for things like door openings.

Fermacell steel studs would attach to this steel frame, then plasterboard attach easily to the fermacell steel studs?

Sure, this would work. This is just a bunch of extra work compared to a wooden frame though.

To build a room inside a room, it's better to use steel studs to construct a rigid steel cage that rests on dampers, like rubber or even shock absorbers. Is this not correct?

In order to properly isolate mass on springs/rubber/etc, serious math and predictions must be made. For example, floating a room is not just building a room on some hockey pucks. So to answer your question, yes, sure you could build your walls and ceiling assembly on some dampening system, but if you're going that far, you should float the entire room. With that comes hundreds of thousands of dollars though. So unless you NEED insane amounts of isolation, the most easy, affordable, and effective method is to build your inner leaf out of wooden studs and attach OSB and/or drywall directly to the studs. The same goes for the ceiling. If you want to save height, the ceiling should be constructed using John Sayer's inside out method. For certain walls or entire rooms, it's often beneficial to build your walls inside out as well!

Greg

[Soundman2020]

Please answer this, cause that's my current understanding. To build a room inside a room, it's better to use steel studs to construct a rigid steel cage that rests on dampers, like rubber or even shock absorbers. Is this not correct?

Adding to what Greg already said: What matters is that there is an "outer" room, and an "inner" room, and they are both built correctly. Both of those can be built with any building materials that provide the correct characteristics. Such as: brick, concrete, drywall on studs, MDF on studs, OSB on studs, or any combination of those (plus others). The studs can be either wood or metal, but there is NO need to have a rigid metal cage specially built: just ordinary metal studs... What matters, always, is that the wall is designed properly. Also, the inner room does not need to rest on rubber dampers: it can, but there is no real need for that in the vast majority of studios. It is only necessary for extreme cases that need very high isolation, in which case the entire room is "floated" on rubber, not just the walls. That's very expensive to do, and very hard to do, as Greg mentioned.

The key here is not the materials: it is understanding the principles, and using the equations. In theory, you can use pretty much any materials, as long as they have the correct mass (surface density) and structural properties.

- Stuart -

[Matt C.]

It all depends on HOW you are doing the ceiling. There are several different methods. If you are doing a modular inside-out ceiling, for example, that's a lot more complex than if you are doing a conventionally framed ceiling. There are pros and cons for each.
- Stuart -

Sorry to leave this thread hanging for so long. I'd be interested in seeing any construction/framing details for either one, but I'm most likely going to end up with a "conventional" ceiling. I attached a picture below that shows what I'm talking about (minus the subfloor and above...). I can see generally how it's supposed to be configured but it's unclear how/where the ceiling joists, rim joists, and top plate all get nailed together.

I've read a couple good books about general framing techniques, but they didn't talk about room w/in a room at all since it's more specialized.

[Gregwor]

For the inner room, just frame up walls like normal and rest ceiling joists on top of the walls. It's really that simple. Just make sure no walls or ceiling components of your inner room touch the outer room!

Greg

[Soundman2020]

but I'm most likely going to end up with a "conventional" ceiling.

How high are the outer-leaf joists above the floor in your case? And how good do you want the acoustics to be inside the room? There are several very good reasons why it might be a good idea to go with an inside-out ceiling. Gaining back all of the height of your inner-leaf ceiling joists is a biggie! If you have 12 foot ceilings, then it's probably not an issue, but if the existing joists are only around 8' above the slab (or less!), then it is a big deal. A very big deal.

I can see generally how it's supposed to be configured but it's unclear how/where the ceiling joists, rim joists, and top plate all get nailed together.

That depends on how you design it! They way I usually do it is to create a "skeleton" of doubled or even tripled sistered joists with fairly wide spaces between them, then raise individual modules (built on the floor) up into those spaces. Each module is 2x4 framing with at least one sheet of OSB/MDF/ply and one sheet of drywall, sometimes more. The joists are whatever size I need for the structural integrity of the ceiling. You can see some examples of that on this thread: ( http://www.johnlsayers.com/phpBB2/viewt ... =2&t=21368 ). Look at the fourth and tenth images on the first page of that. You can see more details later in the thread.

I've read a couple good books about general framing techniques, but they didn't talk about room w/in a room at all since it's more specialized.

Treat it as if it were a large shed with a flat roof: That's more or less the concept you are looking at.

- Stuart -

[Matt C.]

For the inner room, just frame up walls like normal and rest ceiling joists on top of the walls. It's really that simple. Just make sure no walls or ceiling components of your inner room touch the outer room!

Greg

Yes, I understand where the boards themselves go in this case, what I'm trying to get at is: where do the nails go?

[Gregwor]

Yes, I understand where the boards themselves go in this case, what I'm trying to get at is: where do the nails go?

Hopefully this helps:

Ceiling Cross Sectional Detail.jpg

Greg