Confused on how to decouple a ceiling

[throttle]

Please clarify which design I should follow between the following two pictures.

The only difference with my design is that I will not be using RC on the walls. I will be using it on the ceiling.

I am confused if I need the sway bracket or not in the below drawing.

[throttle]

Assuming I use RC on the ceiling, do I still need a sway bracket or should I attach my wall to the ceiling joist per the this drawing?

Again I will not be using RC on the walls just on the ceiling.

[sharward]

Sway brackets (actually "anti-sway brackets") are generally used to secure an inner wall frame to an outer wall frame or a ceiling joist in a decoupled manner.

I think the answer will depend on what you intend to do. If you are building double wall frames, then sway brackets may be needed to keep the wall upright and straight -- and decoupled from the outer leaf.

(In my case, even though I'm doing double wall frames, I was told by my acoustical engineer that anti-sway brackets are not needed, since I'll be sheathing my inner walls with OSB for structural integrity and attaching an inner leaf celing across my inner leaf walls... So that's a double wall example where anti-sway brackets can probably be skipped.)

You say you are "not using RC on the walls," but it's not clear (to me anyway) whether or not you are using double wall frames... ...so it's difficult to answer the question with certainty.

--Keith

[throttle]

Thanks for the reply Keith! Maybe a drawing will make it easier

Note that I "lied" in my first post, I will be using RC on some walls

At the time I thought my question was a simple one, I am mostly confused about using a sway bracket and how important it is not to connect a wall to a ceiling joist.

Sounds like I will need one for the double wall between rooms, but what about the other walls? Should I just have those connect to the ceiling joist or should I use a sway bracket?

(In my case, even though I'm doing double wall frames, I was told by my acoustical engineer that anti-sway brackets are not needed, since I'll be sheathing my inner walls with OSB for structural integrity and attaching an inner leaf celing across my inner leaf walls... So that's a double wall example where anti-sway brackets can probably be skipped.)

Not sure if I understand this design. Can you post a drawing of that wall design? What is OSB and how do you attach an "inner leaf ceiling"? I am not sure I can do that because my ceiling height is low...

Thanks,

Rodney

[sharward]

For the wall that will not be double-framed (the one you're using RC on), you certainly do not need an anti-sway brace. In that case there is no wall frame to worry about swaying.

For the rest of the inner leaf walls, you might. The anti-sway brace stablizes the top of the wall without firmly coupling it to the ceiling joist.

What are your ceiling plans? I'm concerned that while you might have a good plan for your walls, your ceiling may be a weak point. Don't underestimate the power of a bad ceiling plan to render your project a complete waste of time and money!

Here's my latest ceiling plan.

[throttle]

Thanks for the reply Keith.

Here are the details on the ceiling. The basement ceiling right now is just bare joists and the sub floor above. The joists are 2x10 16” on center. Each joist has an 11’ span. The wood is No. 2 SPF.

My plan for the ceiling is to hang 2 layers of 5/8” off of hat channel and RSIC clips. I also plan on using 2.5 pcf Roxul AFB insulation between the joists per John’s drawing in this thread:
http://www.johnlsayers.com/phpBB2/viewt ... t=lighting

For putting the two layers of drywall between joists, I will follow directions per this thread:
http://www.johnlsayers.com/phpBB2/viewt ... sc&start=0

[sharward]

Hey throttle,

Please don't feel "dumb." You're just the opposite for caring about the specifics and your dedication to getting this right!

I can relate to your situation. I discovered this forum a year ago and since then I have learned a great deal. It wasn't easy though. I too have/had no real construction experience. If you've followed my project thread from the beginning, you know how many iterations my plan went through, and I went through some genuinely troubling and frustrating experiences. So, fear not -- if something isn't clear to you in spite of your reading and rereading, and/or if you detect contradictory information here (and elsewhere), then by all means, feel free to ask -- because, chances are, someone else is (or will be) having the same question!

OK, now onto your questions.

Your ceiling plan seems good, but you might be able to do better. While he 10" joists you have offer you a decent depth to accommodate a good air gap, your RC on RSIC clips will ensure that the ceiling is decoupled from the floor above, and your "beef-up" layers between the joists should be able to effectively increase the mass of your upper leaf, there are a couple of disadvantages to that plan. First and foremost is safety -- by adding basically four layers of drywall to those joists, you are adding around 7 to 9 pounds per square foot to the structure. This is considered "dead load" -- meaning, it's permanently attached, unlike furniture or people that come and go. While 11 feet is a pretty short span and 10" joists (Are you sure of that measurement? "Today's" 10" joists actually measure 9 1/4".) are pretty strong, especially on 16" centers, you must make sure that your structure is capable of holding that weight. I cover this in the "Safety During Demolition Construction" sticky thread. Bottom line, don't assume it's OK unless you have the bulletproof calculations and/or the structural engineer's report to prove it, because your life and those of your closest studio buddies depend on it.

Probably a better way to go -- if you don't have any obstructions that would make this impractical -- would be to stagger new ceiling joists between your existing joists and attaching the new joists to the top plates of your new walls downstairs. Here's a thread that discusses the concept, including technical drawings, in detail.

If you adopt the "staggered joists" plan, you won't need to use RC on your studio ceiling, because there aren't any firm connections between the original joists and the new ones. You also wouldn't need anti-sway braces because the top plates of your new inner leaf walls are firmly attached to your new joists.

Your questions and confusion about when and when not to use anti-sway braces may be moot if you go with a staggered joist plan... But just in case you don't or can't go in that direction, I'll do my best to explain. In conventional construction, you have to firmly attach things. But in studio construction, you have to make things strong and sturdy without necessarily firmly attaching those things. The compromise is using "tricks" like anti-sway braces (or RC for that matter) which allows you to give an assembly some strength and rigidity while also ensuring that you're not creating a direct firm path for sound energy on which to travel. (Think of two cans and a string -- pull them tight, and your voice travels along the string from one can to another.)

The purpose of an anti-sway brace, given the goal of the above, is to keep a wall frame steady and upright without leaning into its neighboring wall frame and/or without having to firmly attach (i.e., nail/screw) it directly to the joist above.

In case you're still wondering why I won't need anti-sway braces in my own project, it's because I'm not attaching any of my inner leaf frames to any of my outer leaf frames at all. I'm also going to use a layer of OSB (which I think stands for Oriented Strand Board -- kind of like plywood but engineered with wood "chunks" -- it's quite strong, in the same league as plywood, but usually a little cheaper) on all my framing, as is required by California Building Code for structural integrity (think: earthquakes)... So the OSB will definitely make my "box" very strong and rigid and very unlikely to "lean" against my outer leaf.

I hope that clears things up a bit and gives you some other ideas to think about (namely, the staggered joist thing)... Although that may in effect cause you to have -- gasp! -- additional questions. If so, ask away. If I can't answer, I'm sure someone here can.

--Keith

[throttle]

Thanks for the response Keith. After doing some more research plus a good nights sleep, I started to understand when to use an anti sway bracket.

So I edited my post and deleted my questions. Looks like you just posted your answer right as I was deleting.

Sorry I made you type all that up

I will take some time to digest your ceiling recommendations.

I am very concerned about safety and started playing with the span calculator here: http://www.awc.org/calculators/span/cal ... cstyle.asp

I increased my live load to 60 psf and my dead load to 20psf and came up with a max span of 15’ 5”. So I should be o.k. with 11’ spans correct? Well off to read your thread about the dual joists. I am sure I will be back with questions after I give it a good read. Thanks again for all your help. This will go a long way in ensuring that my contractor gets it right once we start construction.

[sharward]

No worries!

Yeah, my "gut" told me that your joists could probably handle the extra load... But I still like the staggered joists concept more.

What's your vertical clearance -- floor to bottom of joists?

Is this a basement?

Edit: I just found your original design thread, which confirms that it is indeed a basement and that you have "8 foot ceilings" -- but you'll need to be very precise with your measurements, as there are minimum height requirements required by code. Most snippets I've seen indicate it's 7' 6". That's finished clearance, so you need to take your finished flooring and ceiling into account.

--Keith

[knightfly]

Couple of things - unless your place is VERY different, it was framed with #2 and better lumber - my span calculator shows only up to 12'4" span for 2x10's on 16" centers when you choose the lower, more normal grade of framing lumber. Still, you should be fine unless you have already 2" concrete ABOVE your joists...

Be careful when deciding to interleave ceiling joists - besides the lower ceiling, which may put you under height, there is the consideration that your existing joists may have cross-braces or blocking in place; this should NOT be removed because it's purpose is to keep the joists from "twisting out from under" the floor under load.

Probably your best ceiling choice under the circumstances would be to do a double layer of "beef" between joists as detailed elsewhere on the board, then use your RSIC clips and hang the ceilings off those.

If your MAIN concern is transmission of noise to the upstairs, then acoustically you'd be better off making your entire ceiling one continuous double layered expanse hanging from resilient mounts; however, this makes it difficult to keep walls between rooms from falling over...

So it would probably work better to frame in your rooms, keep at least 1/4" to 1/2" of clearance between your ceiling joists and the top of your wall frames, and use a few sway braces to keep them in place WITHOUT hard contact.

Then you would hang your RSIC/channels separate in each room, keeping the ends of the channels at least an inch or more away from walls - you'll get your best isolation in this method if you hang the WALL layers FIRST - see the REFERENCE section for a couple of threads on this - and THEN hang your ceiling layers on the RSIC and channel. Careful caulking using backer rod for EACH LAYER will give you a resilient mounted ceiling with MINIMAL contact with the walls, so there's as much decoupling to the upstairs as is practical.

The attached sketch is similar to what I mean, except it's done in steel with RC instead of wood with RSIC's... Steve

[throttle]

Steve,

Thanks for your reply. After reading your post, plus what I have learned via the span calculator, I have decided not to use drywall between the joists. I would rather have the wife hear a few more db then risk the weight.

So my plan is to use RSIC clips and hat channel for the ceiling with 2 layers of 5/8". I also plan on using the RSIC clips and hat channel on all walls except for the double wall between the vocal booth and control room. (My drawing previously showed not using RC on all of the walls)

I have a question regarding the sway bracket.

I found via the avs.com forum a method using a DC04 RSIC clip. The first picture shows how to use it via a ceiling joist which I need to do with all of my internal walls.

The second picture of the bracket against a concrete wall is at a funny angle, but I think you will get the point.

Do you think it is o.k. to use this method vs. a DIY sway bracket?

Just for final clarification - I plan on hanging the drywall via this thread:
http://www.johnlsayers.com/phpBB2/viewt ... light=rsic

Please let me know if there is a more up to date version of this or if I am good to print it out and add it to my "How to build a studio” manual.

Thanks again for everyone’s help. Now I am off to do more research on HVAC

[knightfly]

Those particular RSIC clips will work fine for sway brackets; all you need is to limit horizontal movement without using hard contact between components, and that does the job.

That link is as recent and accurate as anything for drywall info... Steve