Critique my ceiling design please...

[Dr. J]

After reading the sae info and posts here, and a wonderful book, I have
come up with this ceiling design for my studio.

I am trying to kill as much sound transission to the upstairs as possible,
(making my wife happy) while not being able to have a floating ceiling due to a low 7ft.

Here are my specs & challenges...
7ft ceiling
In basement
2 walls are cement.

Will this attached plan work well? I have added another layer of rigged glass in the plan, hoping this will cut out sound aswell.

Thanks for any input,
J

[JRSGodfrey]

I'm in almost the exact situation -- 7' ceiling in a masonry, bunker like garage. After asking around and seeing some similar designs, I came up with this. It should allow for good isolation and do some acoustic treatment as well (or I've been lead to believe).

My sandwich, up in between the joists (not a new idea by any means):

subfloor above
mass loaded vinyl
resilient channel
2 layers of 5/8" sheetrock (plenty of caulk)
air
loose fitting rockwool or fiberglass
fabric stapled to joists, or cap it off with 1" rigid fiberglass panels.

I've been told this will give you two things -- decent isolation from above space and at the same time an "acoustically higher" sounding ceiling. Plus you lose zero height. If there isn't enough isolation, drop another 1/2" of sheetrock from hangers attached to the RC -- if that's feasible, I've not asked about that.

I'd love any and all input on this idea. Also, I'm sure I need to be sensitive to the load this would put on the floor above. My joists seem to be about 2x10 and are 12" apart (the house was built in the late '30s).

Good luck!

Jay

[knightfly]

J, you were into Rap/R&B, right? And you wanted as much isolation as you could get?

If so, check out my modification of your design - this should help by at least 6 dB - putting the double layer of sheet rock up against the floor, caulked and cleated between each pair of joists will increase the mass of the upper leaf. That will improve low frequency TL.

Putting the soft fiberglas against each leaf will dampen the leaves, which minimises the effect their resonance has on Transmission Loss at their resonant frequency. Using the soft fiberglas in those areas won't cause any bridging effect.

The different masses of the upper and lower leaves will eliminate the chance of having the same resonant frequency in both leaves, which will also improve TL.

[knightfly]

JRS, sounds like you've been looking at something like John's "inside out" walls - that will work, depending on just how much isolation you need between upstairs and down.

With 2x10's on 12" centers, you should be able to put just about anything you want between/on/under them and be fine.

If you want really good isolation and STILL need all the headroom you can get along with some "free" ceiling treatment, you could try putting solid cleats along the joists about midway between the top and bottom of the joists, fasten Resilient Channel to those cleats, fasten two layers of 5/8" sheet rock to the Resilient channel, caulk really well with Acoustic Sealant, and THEN put your spun fiberglas in between the joists and then cloth-covered 2" rigid fiberglas even with the bottoms of the studs.

The resilient channel won't do as much for isolation as it would across the bottoms of the joists, because the edges of the joists are exposed to the sound field downstairs and connected to the subfloor upstairs. Still, they should help quite a bit along with the two layers of sheetrock - placing the sheet rock midway of the joists will at least give you SOME airspace BETWEEN the two leaves of the ceiling, while still leaving room for acoustic treatment under.

If that wasn't clear enough, post back and I'll do a drawing... Steve

[JRSGodfrey]

Knightfly,

Thanks for the suggestions/modifications. I would like to get as much isolation as possible while avoiding lowering the ceiling AND get some acoustic benefits (a lot to ask for, I know).

The ceiling area in question is about 6x8 and directly over the console,speakers, and mix position. The remainder of the ceiling is concrete slab. You can see the drawing of my whole setup in the "I Invite Your Comments..." thread in Studio Design.

The only thing that I'm a little vague on is the cleats. I can visualize what they would be, but what are they specifically?

Also, what would you think about lining the inside area of the joists with some kind of flexible decoupling material to further isolate the sheetrock on the RC from the joists? The sheetrock could be cut to snug-fit to such material.

Also, any benefits of rockwool over fiberglass or vica versa for the fill? I've read on this board that rockwool absorbs better at low frequencies.

Thanks in advance.

Jay

[knightfly]

Jay, check the drawing I did - I wouldn't recommend this if you possibly have enough headroom to put Resilient channel UNDER the joists, but it will work as well as anything you could do if you leave the bottoms of the joists exposed to the sound field.

You can use either Rockwool or 703, Rockwool does a little better at low freqs.

The spun fiberglas is there to dampen the panels, which should also lessen the flanking effect of the continuous wood joists between the upper floor and the sound field.

Be sure to get REAL acoustic sealant for all the RED areas, regular stuff won't work ESPECIALLY at the edges of the lower sheet rock layers.

Sorry this is so succinct, I had a more involved answer ready to go and slipped - it went bye-bye -

Any questions, come on back... Steve

[JRSGodfrey]

Steve --

Succint is fine -- in this case better than fine. Thanks for the extra effort. One hopefully not stupid question: In the diagram, is the resilient channel parallel or perpendicular to the joists? I assumed perperndicular, but the drawing is throwing me.

I'm off to Paypal the forum in thanks for yours and John's excellent advice.

Thanks again. When I actually get down to building it, I'll check in.

[knightfly]

JRS, we at the forum thank you for your help -

And, I intended for the RC (and cleats also) to run parallel to the joists in this case - it would be too much of a PITA to cut short pieces and fit them between joists without taking the risk of leaving them too long - you would NOT want the RC to touch the framing on the ends of the RC.

My drawing would give you full length RC down each side of each joist cavity, and at 12" centers would support up to three layers of wallboard if necessary, as long as the cleats were strong enough... Steve

[JRSGodfrey]

Steve,

Thanks for the clarification.

Just did some surfing for resilient channel...

single leg vs. double leg -- now I get the drawing.

Cheers,

Jay

[buddhajuke]

Any questions, come on back... Steve

This is exactly what I was looking for as well... just one question:

How would you lay it out for 6" joists? (To get the similar results, albeit less effective)

[Museth]

What an amazing thread. I am less than two weeks out from finishing and stumbled across this just in time. I second buddhajukes question. I'm trying to get the double whammy of absorption and isolation with just shy of 7 foot ceilings in a basement studio build. Joists are 7 inches deep and cavities are 14 inches wide? Any suggestions to those of us with not quite as much depth in the joists? Also, seeing the age of the thread, any results or reports on how things worked out after said treatments of the ceiling?