John Sayers' Recording Studio Design Forum

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