John Sayers' Recording Studio Design Forum Archive

Ok, so this is an easy general question - that I can't find the exact sequence of steps for drywalling and caulking a single frame 2 leaf wall. Let's just focus on the one leaf... what are the steps once the wall is framed, electrical is run etc.?

Assume the inner leaf will NOT be on RC and will just consist of a layer of 1/2" and 5/8" drywall screwed to the studs.

Where do I caulk? Do I start caulking the perimeter of the wall before hanging any drywall? Do I then caulk around each sheet of drywall? and then squish the next piece of drywall to the other already hung piece of drywall repeating this til all drywall for the 1st layer is done?

Or forget that - Do I just run some caulk over the joint between each piece of drywall? Then how does the drywall joint compound and tape work on top of that?

Or is it just use acoustical caulk wherever there is a small gap (along the floor and ceiling perimeter) and just drywall as normal... hang drywall, tape, joint compound, screw next layer with 1/4" gap from the floor and repeat?

I just can't find the clearest instructions on the actual steps of hanging the drywall and doing caulking for a studio type wall...



I do not want to forget any important steps...


thanks,

David

OK, in order -

Normally a single layer drywall install has the drywall going horizontal the long way - this improves the look of the final job due to longer spans between vertical joints, and somewhat increases strength (drywall has different bending strength lengthwise than width-wise)

So, for a multi-layer wall you want to END with a horizontal application - this means that for 2-layer, you start with vertical and end with horizontal. For a 3-layer, you'd start and end with horizontal, with a vertical layer in between.

Caulking isn't needed at all until after you have the first layer up. There's no need to caulk the frame, all it's doing is supporting the drywall which is your "barrier" -

Place the first layer, using half-schedule fastening (screws twice as far apart as normal) - take some scraps of 1/4" ply or equivalent thickness and use them for "shims" along the floor, and tape some on the wall where the new wall will intersect - these will keep the new wallboard 1/4" away from floor and intersecting walls. After fastening, pull the "shims" - mud and tape this layer as normal, being careful NOT to mud around the perimeter. Wallboard is tapered along the long edge for mud, so be sure to treat this seam as normal drywall finish coat, bringing this "taper" up level with the rest of the wall - you do NOT want any VOIDS between layers. Along this line, also remember this TAPER is only on ONE side of the boards, so it must be placed to the side AWAY from the frame for each layer.

After mud and tape (and light sanding), insert foam backer rod and caulk the perimeter of the wall, where it butts up to floor, ceiling, other walls - if you're also doing a new, suspended ceiling, you can alternate layers - wall layer, ceiling layer, caulk - wall layer, ceiling layer, caulk - OR, you can put all wall layers up first and then suspend the ceiling layers on RC, caulking each layer as you go.

The alternating layer method is a bit stronger - the "wall first, ceiling last" method may give slightly better isolation.

Second layer goes up same as the first, only BEFORE you start place masking tape all around the wall on ADJACENT surfaces, and mark EXACTLY where each screw is located - these are places you do NOT want to drive a screw for the second layer, because you will tear up the wallboard and create a weak spot there. Once your second layer is in place with corners and center fastened, you can snap a chalk line to show where each row of screws are in the FIRST layer, to make it easier to miss them.

This pre-supposes that you've placed the first layer's fasteners IN A LINE and not haphazardly. Again, a chalk line will help here. Your masking tape markers can (and should) actually be put up BEFORE you start fastening, so you can use them as a guide to snap to - you can mark each location with a "1" or "2" to designate which layer that screw is used on.

If you're going to take a few days for the whole wall, you should spend more and get the "blue" masking tape - it comes off without residue much easier.

Second layer - place your shims around the perimeter, set the boards on them horizontally, fasten the 4 corners and a couple in the middle, finish the rest of the wall that way including the upper row(s) - then, snap chalk lines where your "2"'s are, and do full-schedule screws (these need to be longer by at least 5/8" than your first layer screws - 1-3/4" to 2" for 1/2-5/8" combo) -

Now, mud and tape, pull the shims, finish sand the wall, vacuum, then caulk the perimeter thoroughly again, also using foam backer rod under the caulk bead. If you put up a molding for looks, it should be GLUED to either the wall or floor but NOT BOTH - it's better to glue to the wall, using thinner shims under the molding to give just enough space NOT to couple the wall to the floor.

Corner moldings - the newer "flex" plastic corner moldings work well, just don't mud in the corner itself - you want this part to remain flexible to keep wall/wall coupling to a minimum.

Paint your favorite shade of cool... Steve

Great summary Knightfly.




I see my lower picture has a different drywall order than you're suggesting. hmm.
Unless one does two layers of walls first, then two layers of suspended (kenetics ICW) ceiling, it probably doesn't make a difference -- sooner or latter the zig zag would catch otherwise.

Yeah, there's two schools of thought on ceilings - yours (and Rod's) and others - the idea of the zig zag will of course give a likely more reliable airtight joint under more conditions, but there's another concept that doing this on a ceiling could cause the ceiling layers to sag enough to cause hard contact between ceiling and wall layers - this can (arguably) lessen the overall isolation of the room by coupling the wall leaves to the ceiling leaf.

The "all wall layers first" method relies on the resilient mounts for ALL ceiling support, so If I were doing it that way I'd likely go for RSIC and hat channel for the extra strength - if/when the ceiling sagged any, a decent grade of caulk should have enough flex for it NOT to become a seal problem.

I've either not seen or don't remember an exact figure for difference in overall isolation, but seems like it was only a couple dB at most.

Got a coin?

BTW, nice drawing, thanks a lot... Steve

OK Folks,

I was asked a question by our friend Z - and had posted a response to it before we got hacked........ and now it's gone.

SO I will repost what I explained.

The question related to my telling someone that they could tape the final finished wall product and then paint it if they so choose.

Z then questioned taping the corners at walls/walls and walls/ceilings - this due to the caulk details there.

My response follows:

Z...........

All buildings have movement of the walls/ceilings and only in extreme cases do the joints crack. Movement is caused by the fact that no frame is truly rigid - all frames move under wind - snow loads - seismic conditions - changes in relative humidity - etc, etc, etc.

One way to deal with this (in extreme cases) is the method I was taught by an OLD plasterer doing repairs on a real old church that was listed with the historic society.

He was using the nylon screening material (what is used for window screening) to patch plaster cracks.......... and when I questioned him on this application (I had never seen this done before) he explained that the elastic properties of the mesh would stop the crack from translating to the surface.

I have done this sucessfully in the past with no bad results.

On now to caulking and then taping the corners.

In our hotels we use this method for isolating our guest rooms, and in the case of the 21 story hotel I am currently watching go up, also for the exterior wall (isolation from the nearby 8 lanes of interstate).

We have to tape the corners as a finished base for the wall paper and (or - depending on the location and finish) for paint.

We don't have problems with cracking.

Thus - if what you want is a good finish without corner moldings - it is acceptable to rake the last layer of caulk back slightly (from the face of the drywall) and then tape the corners as you normally would.

Remember - there is a connection point there regardless - your horizontal and vertical tape joints have to finish up to the end of the sheet - and thus to the caulk.......... I sort of like the idea of the final coat of tape on corners tying this al together.

One other thought on this - the walls tie together at the corners - once they are joined they should move as one (as is the case with standard wall framing).

The ceiling should develope whatever sag is going to occur (under dead load) within a few days of hanging (probably hours but I cannot prove that through actual test results) - once this occurs there should not be any more "sag" developed substantially within the life of the structure......... no different that any other construction method.

The 1/4" to 3/8" clearance is required only to allow enough movement of the joint so that NORMAL movement can be maintained without compromising the caulk joint........... nothing more - nothing less.........

Thus - taping this as a final finish - as would be done with any other normal drywall package - should never be an issue.


Sincerely,

Rod

Hey, this just occurred to me... All of this discussion seems to relate to inside corners.

What about outside corners? Do the same rules apply?

--Keith

is it "better" for isolation to tape and mud or use acoustic sealant/backer rod? on the no perimeter joins?

thanks
g

Hey all -

Had a quick question regarding the (very helpful) diagram posted at the beginning of this thread by z60611.



Looking at the first layer of ceiling (layer #1,) does that butt up flush against the interior wall frame around the entire ceiling perimeter?

And are we suggesting that the entire first layer of ceiling in the entire isolated space go up before hanging any actual "wall" sheetrock?

Thanks!
Nick

Sorry. Had also hoped to clarify one other thing...

Assuming I'll be building a room within a room (in which the new ceiling is supported by the new interior walls,) would I essentially frame all four interior walls first and then frame the new ceiling?

How does one connect the new ceiling frame to the interior wall frames?

I had seen a detail of this in the reference section, but I wasn't 100% clear on how it worked.

Thanks, you guys.

if a floating floor is not usually necessary when you are building on a concrete slab, then what about the floating ceiling?

Yes. The diagram isn't very clear on that, but yes, there is direct contact there, usually. You could leave a gap if you wanted, but it isn't really needed (except to get a better seal!)

And are we suggesting that the entire first layer of ceiling in the entire isolated space go up before hanging any actual "wall" sheetrock?

Not necessarily. You can do the first layer of the wall first, if you want. Since there's a gap larger than the thickness of the ceiling drywall, you can insert the ceiling panel above the wall panel, then nail it in place and seal it. Then do the second wall layer, second ceiling layer, third wall layer, third ceiling layer...

would I essentially frame all four interior walls first and then frame the new ceiling?

Right. That's the normal procedure.

How does one connect the new ceiling frame to the interior wall frames?

With nails? Seriously, there's a couple of methods. One is to use joist hangers to attach your joists, the other is to rest the joists on top of the walls. What I often do is to have larger framing members, widely spaced, across the tops of the walls, then raise the ceiling as a series of "modules" that fit in between the larger members, one at a time. Seal and bolt in place. If you keep your modules to a reasonable size and weight, then you can raise them with a single standard drywall lifter. Or if you work carefully, with a pair of drywall lifters in tandem, for larger modules. But do work safely! A module like that can weigh a LOT! You don't want it coming down on your head... or any other part of your body!

- Stuart -

Thanks, Stuart!

Hello -

(Hopefully no one minds that I am reviving this very important thread).

I thought it worthwhile to summarize the options for the transitions (corners).

Here is a drawing I created in attempt to capture the differences. Here I show the transition from a ceiling (hung with clips and hat channel) to the outer layer of a decoupled soffit frame; both are thus inner leaf barriers. I drew for 2 layers of sheetrock/drywall/gypsum with GreenGlue between, but one may easily extend to 3 or more layers. The numbers refer to the step order.

Please let me know if these options are accurate, and exhaustive of the (good) possibilities.

If they are, then a few questions arise; any input appreciated:

1. What are the pros/cons of each method?

2. Should one leave the small air gaps (white spaces) which may occur, or fill them completely with caulk?

3. Is the 1/4" gap just to allow insertion of sealant, or is it also to decouple the frames surfaces? (Since they are part of the same leaf, I would have thought decoupling is less important).

4. Is there a good way to build without the gap, corners tight, without need for backer rod at all? A lot of illustrations and instructions online seem to show no gap, just a tight fit of the panels at all corners. (I believe Rod Gervais and others mentioned otherwise that this is not a good method since it relies on just tape for seal. But maybe there is a better way to seal it, like applying some thin sealant on the edges. Of course, if part of the goal is to de-couple the surfaces from each other (question #3 above), then this tight-fit approach is a no-go, since it would couple the surfaces.

5. What is the process with more complicated structure. For example, if inner leaf is wall-soffit-ceiling, does the alternation simply go bottom-up or top-down for each layer? (e.g. wall, soffit bottom, soffit "wall"/side, room ceiling; or vice versa).

(I want to draw this as clearly as possible, both for my own understanding and for the contractors. Tomorrow I'll meet with them and see if they already understand this zig-zag/overlap technique)

P.S. Are there any links to info on the relative isolation provided by 3 layers of sheetrock/drywall/gypsum instead of 2? I seem to recall that it becomes a matter of diminishing returns, but can't find the source.

One thing I've not been clear on is whether or not it is necessary to tape and float joints on the inner layer(s)? Can you just caulk the inside layers or do you also have to tape and float those as well?

Here is a drawing I created in attempt to capture the differences.

Either 1 or 2 is fine. Definitely not 3. Personally I prefer #2 but renumbering the layers, so your layer 2 is first, then your layer 1, then your layer 4, then your layer 3. If you do it in that order, then the drywall on the wall gives you a small "ledge" to rest the ceiling drywall while you are maneuvering it into place.

However, I'm curious about this:
What's going in there? What's the light grey and dark grey, and the black channel-thingy? To me it looks like your inner-leaf is coupled to your outer leaf there.

to the outer layer of a decoupled soffit frame;

How is it decoupled? That's not clear from the image. Indeed, from the image it looks like it is coupled!

Should one leave the small air gaps (white spaces) which may occur,

There should be no air spaces. If you push the backer rod in deep enough, then caulk well, there would only be very minor air spaces in there between the round backer rod and the flat drywall faces. That's not a problem at all.

Is the 1/4" gap just to allow insertion of sealant,

What '1/4" gap'? I don't see that marked on your diagram.

Is there a good way to build without the gap, corners tight, without need for backer rod at all?

No. Because that would not allow for good sealing. If you cannot get backer rod where you live, then you can do two layers of caulk instead, with the first layer replacing the backer rod. Wait until that is dry before you do the second one.

A lot of illustrations and instructions online seem to show no gap, just a tight fit of the panels at all corners.

That might be the case, but that's probably just for clarity, not actual construction practice. In the studio designs that I do for paying customers, I don't show those gaps, since it's a lot of extra work to model them. I just mention them in the notes or explanations. Just like I don't show where to put every single nail or screw: some things are taken for granted in construction, and there's no need to detail them on the plans or 3D model.

Rod Gervais and others mentioned otherwise that this is not a good method since it relies on just tape for seal.

Right!

Are there any links to info on the relative isolation provided by 3 layers of sheetrock/drywall/gypsum instead of 2? I seem to recall that it becomes a matter of diminishing returns, but can't find the source.

Here's your answer: Don't guess! do the math to make sure that you really will get the correct MSM resonance frequency, and the amount of isolation that you need, at the frequencies where you need it. Here's what you need to know:

The equations for calculating total isolation of a two-leaf wall are simple:

First, for each single-leaf barrier individually you need the Mass Law equation:

TL = 14.5 log (M * 0.205) + 23 dB

Where: M = Surface density in kg/m2

For a two-leaf wall, you need to calculate the above for EACH leaf separately (call the results "R1" and "R2").

Then you need to know the resonant frequency of the system, using the MSM resonance equation:

f0 = C [ (m1 + m2) / (m1 x m2 x d)]^0.5

Where:
C=constant (60 if the cavity is empty, 43 if you fill it with suitable insulation)
m1=mass of first leaf (kg/m^2)
m2 mass of second leaf (kg/m^2)
d=depth of cavity (m)

Then you use the following three equations to determine the isolation that your wall will provide for each of the three frequency ranges:

R = 20log(f (m1 + m2)) - 47 ...[for the region where f < f0]
R = R1 + R2 + 20log(f x d) - 29 ...[for the region where f0 < f < f1]
R = R1 + R2 + 6 ...[for the region where f > f1]

Where:
f0 is the resonant frequency from the MSM resonant equation,
f1 is 55/d Hz
R1 and R2 are the transmission loss numbers you calculated first, using the mass law equation

And that's it! Nothing complex. Any high school student can do that. It's just simple addition, subtraction, multiplication, division, square roots, and logarithms.

One thing I've not been clear on is whether or not it is necessary to tape and float joints on the inner layer(s)? Can you just caulk the inside layers or do you also have to tape and float those as well?

That's about aesthetics, not acoustics: If the wall will be seen inside the room, as part of the final finished surface, then yes, I would very much suggest "mud and tape" before you paint. In that case, do not caulk all the way to the surface: leave a small gap so there's space for the mud. But if the wall won't ever be seen (eg, if you do an inside-out wall, or if it will be completely covered with other treatment), then it isn't necessary to mud-and-tape it, since it won't ever be seen.

- Stuart -