John Sayers' Recording Studio Design Forum

When doing two layers of sheetrock w/ green glue, does the first layer need to be taped and mudded? Thanks.

Green glue doesn't modify the installation one bit.

Any joint in the field of the panels gets mud and tape. The vertical and horizontal joints at the edges of the panels that intersect the other wall boundaries, use backer rod and acoustic caulk.

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.

So, I take that as a yes?

Regarding 2 [or more] drywall layers ...

It is very important that the 2nd layer overlaps the seams of the 1st layer !

As to mud AND tape on that 1st layer ...

No doubt, getting a complete seal on that 1st layer would be advised. [as xSpace said].

The 'question' may be more with regards to 'TAPE' ... and THAT may have alot to do with
the way the drywall gets hung ... and the tightness [or lack] of the adjacent seams line up.

With tight seams ... you 'may' be able to just mud them ... but then ... make sure you allow
enough time to pass, that when it drys, you have a good seal !

Same goes for caulking the corners, ceiling & floor edges ... When that caulk settles, you
may be surprised to find open GAPS !!! In my build, I found a couple of small sections that
I thought were sealed well .... but fortunately I gave enough time to let everything settle
and then go back in and re-seal [touchup] to make SURE there were no air gaps.

If you can ... don't be in a hurry with this aspect ... oh ... and buy caulk by the case


hope that helped.

"With tight seams ... you 'may' be able to just mud them ... but then ... make sure you allow
enough time to pass, that when it drys, you have a good seal !"

No sir you do not. What does the mud actually do? It sticks to paper and dries hard...hard, right? So what happens to something that is hard when it get continued vibration, and we are not even in the music spectrum yet, we are talking about the environment that makes the structure vibrate, it's below the threshold of human hearing and most often below the threshold of the ability to feel the vibration. These are the vibrations that change a solid structure into a cracked structure, with gravity, and erosion , etc, etc.

But what happens when you place a material that is flexible into this hard substrate? The flexible material will not break and create cracks, like using mud only and expecting this to pass.

Now, in your support, I have seen people use acoustic caulk on the horizontal joints in studio builds rather than mud and tape. This is a "choice" an alternate method.

But using mud alone is not only not a choice, it is not going to work effectively for any length of time.

Oh, and then there is the always tricky third reason...the fire rating of the panel.

The fire rating of the wall assembly "depends" on this construction method in order to achieve the one hour, one hour thirty minute, etc. etc. stated. When fire is trying to breach an gypsum board wall assembly, fire works just like anything in the world...it migrates to the path of least resistance and in this case it searches for air supply which cracks produce. Remember that group? Maybe not

So the path of least resistance in search of food, with mud only...is the butt joint, no matter how tight it is. Acoustic caulk, to my understanding, will not reduce the panel assemblies fire rating.

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.

As always ... THANKS for [again] taking the time to detail the reasoning !!

I recall when building my room, this issue came up. The drywall 'guys' thought I was nuts.
True as THAT might be ... I did following the mud/tape rule on both layers. [... and REALLY,
you only get one shot at doing it right on this procedure, and it only takes a couple days
to do this] ... gives you time to check all your caulking work.

To add to xSpaces post ... I found this additional link that may also help:

viewtopic.php?f=2&t=17006&p=121540&hilit=mud#p121540

... always trying to learn ... sometimes it has to be BEATEN in

... earthquakes... I can tell you all about those! Even with good mud and tape, drywall still often cracks at the joints in earthquakes. Saw a lot of that a couple of year back, here where I live... When things are moving so much that you can't even stand up or walk, drywall tends to come apart at the seems, quite literally. Weakest link and all that.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

I was thinking more due to the vibrations of the Earth, the settling of a structure...not an Earthquake...a little piece of paper /mud/sheetrock...it all gives way with an Earthquake.

If it can break concrete, what do the above three stand against the forces of Nature:?

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.

See also viewtopic.php?f=2&t=17006&p=121496&hilit=mudding#p121496 however.

_________________
Brian
As you slide down the bannister of life, may the splinters never point the wrong way...

Thank you, gentlemen! Not what I was wanting to hear (taping & mudding is a CHORE!), but good to know if I want it done right. Also, when attaching to the hat channel...I don't have any joists within 6" of the ends of the hat channel (6" being the maximum cantilever for the hat channel), can I cantilever sheet rock beyond that and if so, how far?

However? It reads like what has already been said, right?

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.

Any cantilever you do with sheetrock is asking for trouble. A few inches maybe as long as there is a connection at that "few inches" point...but ideally, you wouldn't want to do this.


Give us a picture of this area for better interpretation.

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.

I guess it's not a true cantilever as the next step over is the wall. Intuitively I would guess 6" would be ok as that's the maximum distance the first row of hat channel can be from the (parallel) wall and the maximum "support" is 48", which is what the wall would be doing...supporting the ceiling, right? (I'd do pictures, but don't have a digital camera , so I hope I'm clarifying things. )