I'm not sure I fully understand Steve's instructions on fastening a second layer of wallboard (sheetrock/gypsum/drywall) to a first layer of drywall on a WALL. I always thought you would secure the screws from EACH LAYER OF DRYWALL into each stud, just making sure you don't hit screws from a previous layer of drywall. According to his comments, you could loose 9-10 db of isolation if screws go through BOTH layers of drywall into the studs. Constructing this way would mean the second layer of drywall would only be secured by being screwed into the first layer of drywall.
Here are the instructions from the post...
5. Fastening a second layer of wallboard to a first layer, when the first is mounted on WOOD studs, should only be done using 4" wide stripes of slightly thinned joint compound over the stud area, then fastening with Type G laminatings screws approximately 2-3" away from the studs and parallel to them, on approximately 12" centers. This allows the two layers to act as separate panels, which maintains each panel's coincidence dip separate from the other. It also keeps any fasteners from penetrating BOTH layers of wallboard AND entering the WOOD studs. NOT doing this will lose about 9-10 dB of isolation due to flanking through the fasteners and into the studs.
(BTW, the post is here...
viewtopic.php?f=2&t=529&start=0&hilit=ok%2C+luke%2C+here+goes)
Is he saying to:
Put a 4" stripe of slightly thinned joint compound *ON* the 1st layer of drywall over EVERY stud area (where the screws are secured in the stud through the 1st layer of drywall), fasten type G laminating screws 2-3 INCHES AWAY from each stud INTO THE 2ND LAYER OF DRYWALL PENETRATING AND SECURING INTO THE 1ST LAYER OF DRYWALL, WITH THESE SAME SCREWS RUNNING PARALLEL TO THE STUDS (VERTICALLY) 12 INCHES APART?
If this is correct should the screws going into the 2nd layer of drywall pass through the "slightly thinned joint compound stripe"?
The statement about the coincidence dip definately makes sense, it's only how that 2nd layer is secured that makes me
:shock:
I see this post is almost 6 years old, and heck, maybe I'm just looking at this wrong, but I gotta ask!
Thanx!
Page 125 of the USG sheetrock install manual:
"Strip Lamination (vertical face layer, sidewalls only) This method is
often preferred because it requires less compound and improves sound
attenuation. Apply strips (4 beads, each 3/8" wide by 1/2" high spaced 1-
1/2" o.c.) 24" o.c. max. Place permanent fasteners 24" o.c. max. at each
end of the face layer. Drive type G screws as shown in diagram."
Same thing, excepting that USG is using the word "strips" of compound, implying that a deep notched trowel be used to generate the strips for this lamination process. The compound in this instance is used to laminate or "glue" the layers together, with screws being used sparingly.
It should not surprise you that you do not want the fasteners to bind the layers up on the same support material. Everything that is looked at in these builds is about decoupling, flexing ability, etc.
wtf :shock:
the first time i read this.
has rod mentioned anything about this in his book?
c.
The type G screws are a special coarse-thread laminating screw. After the laminating compound dries, you remove the screws from the second layer and finish the wall.
For clarification on which is permanent and which is not:
"On walls, permanently attach the top and bottom of the face layer with
fasteners driven 24" o.c. maximum. Provide temporary support
fasteners, or type G screws 24" o.c. maximum in the field of the board."
edit: This is aimed at vertical wood framed walls and does not apply to metal studs OR ceilings.
That's an old post and that method is no longer being recommended. See the comments in red here:
viewtopic.php?t=503WOW!
Thanx a bunch dfeiszli!
I guess that's a DEAD issue...
COLD CASE #276 "SOLVED"
How is it settled?
Based on what you guys are reading, with the information you are looking at, what is the method for attaching a second layer of sheetrock to the base layer?
As I read it, Rod's recommendation appears to be for half-schedule fasteners for the base layer, then full-schedule for the face layer, going through to the studs in both. In other words, flanking is not a concern between each layer of sheetrock (at least not compared to the whole thing falling down!)
Are you using green glue in this method?
I'm not building anything yet myself, but from what I can tell, that's the best method to use with or without Green Glue.
This is Steve's 2006 updated response on this subject via the link in dfeiszli's post above...
Just got off the phone with Rod Gervais, a member here; Rod also moderates the acoustics forum on RO, and has more construction experience than most entire construction companies - he and I are in complete agreement on the following, confirmed by our phone conversation.
USG, on page 118-119 of the USG construction manual, (once we deciphered it) does indeed say that it's OK to use strip lamination and laminating (Type G) screws for face layers on sound walls - they recommend only about 6 actual permanent fasteners per sheet of drywall, placed across the short end of the sheet - then, a stripe of joint compound next to each stud (placed immediately prior to installing laminating screws) and about 5-6 laminating screws per sheet (look at the manual, there is a a diagram next to the text on those pages)
Both Rod and myself do NOT, repeat NOT, recommend this type of construction - neither of us has a high enough confidence level in joint compound to trust a wall with only 6 "real" screws to stay put with building shifts due to seismic, humidity, wind and temperature changes, especially since joint compound does NOT stay flexible enough to stay strong through all the normal movement of a building.
The concerns of some over flanking noise caused by fasteners going all the way through several layers of wallboard would ONLY be valid if that wall were a single frame wall with NO separation of the two leaves - as soon as you put up RC or separate frames, you've broken the flanking path to a large degree - the addition of a full cavity of fiberglass insulation finishes the job.
As pointless as it would be to use standard, fully coupled walls for sound attenuation, the use of any glue to avoid through-fasteners becomes a NON-issue -
Since this post is locked, please direct any comments to the "glue and screw" thread, located here -
http://www.johnlsayers.com/phpBB2/viewtopic.php?t=1603
I take this as saying neither Steve nor Rod approve this type of frame/drywall construction and that unless the frame is a single frame with no separation, having seperate frames (and insulation in those frames) would break/reduce flanking noise.
In other words, you would attatch your screws for each layer of drywall into each stud.
Flanking was never a question from what I was reading or even from where I am thinking.
USG knows their business, because it is their business to know what their product can or cannot do.
As to a wall falling down, this is naive to even suggest.
A well installed base layer will not come off the wall, I don't care what you do to it. And adding sheetrock mud as a bond between the two, well, have you ever bonded two pieces of sheetrock together? It's like a metal weld. The joint is stronger then the individual pieces.
So now that we have nothing but the USG handbook and mostly confusion on the other part of who said what, I personally prefer to go with what the maker stated until no shadow of a doubt information is presented to the contrary.
Respectfully,
Brien
As far as preferences, I totally agree Brien...
Each of us takes in the info, evaluates it and come to our own conclusions. You may decide to do it one way, I may do it another. As long as you, (and I or anyone else) knows the consequences of what we decide "to do" or "not to do", I'm personally ok with that. After all, it's our own individual projects right??
High five to you & wishing you many Blessings!! :)
Yes sir, I think you are most correct. It would be a most welcome addition if Steve or Rod would shed some light on this gray area.
xSpace wrote:
Flanking was never a question from what I was reading or even from where I am thinking.
USG knows their business, because it is their business to know what their product can or cannot do.
As to a wall falling down, this is naive to even suggest.
A well installed base layer will not come off the wall, I don't care what you do to it. And adding sheetrock mud as a bond between the two, well, have you ever bonded two pieces of sheetrock together? It's like a metal weld. The joint is stronger then the individual pieces.
So now that we have nothing but the USG handbook and mostly confusion on the other part of who said what, I personally prefer to go with what the maker stated until no shadow of a doubt information is presented to the contrary.
Respectfully,
Brien
I installed the second layer of drywall using joint compound trowled over the entire sheet and hung it with type G laminating screws. I removed the screws and finished the wall. Had no problems. If you laminate the sheets with drywall compound, it's not coming apart unless you rip it down.
Which is another option that USG recommends, excepting that fasteners of sufficient length be used to penetrate both layers from the face layer into the framing members at very top and very bottom of a two layer panel, 24 inches on center.
I did mine like that two years ago as well.
Hmm... I just re-read that thread and the one below and now I'm not sure exactly what Rod is suggesting in place of the strip laminating method.
In the last post in this thread:
viewtopic.php?p=12665
Knightfly says not to bother laminating layers, just screw each one to the studs without bonding them together, and he mentions falling walls as a consequence of the laminating screw method. I can't claim any expertise on this stuff, just trying to pass along what I hear from people who seem to know what they're doing.... Of course this thread pre-dates the other one I linked to, so it's possible the above may be subject to rethinking as well. I thought I remembered reading a consensus between the two of them on what exactly the recommended method was in detail, but now I can't find that anywhere.
I'm with ya. Knightfly also says this:
"Viscoelastic stuff - really expensive, hard to get uniform, questionable benefit. "
That is green glue :)
edit: Many here and else where think that green glue is the be all end all. Me personally, having nothing to compare to, don't see any lose on my end and may not know it if I even used it!
xSpace wrote:
I'm with ya. Knightfly also says this:
"Viscoelastic stuff - really expensive, hard to get uniform, questionable benefit. "
That is green glue :)
That's funny, I didn't even catch that part! Hmm....
OK, here's some related info on the reasoning behind avoiding lamination:
viewtopic.php?p=32330#p32330
I'm not going to read the link, because I already had it explained to me once.
I'm just going to do what I do until a bigger name explains a better way:)
edit:Ok I did peek at it. You will notice that as you keep looking for the "final" on this, the date gets more current.
edit01:bigger name meaning someone other then the few of us AND with current information not something from four years ago that may have now been rethought out.
As to a wall falling down, this is naive to even suggest.
So you think Rod and dfeiszli are naive when they say that using a grand total of only six screws to hold up two layers or 5/8 drywall is not a good idea? so you think it is fine to do that, and no amount of settling, movement or earthquakes could possibly tear lose those six screws?
Hmmm.... Thanks for the opinion, but I think I'll take Rod's "naive" advice on that one!!
:)There is a huge difference in a wall falling down and a piece of sheet-goods becoming lose enough to fall down.
Don't mix up the words.
In any event, you sir are free to do as you see to do.
Anyone interested could do a simple test: get a couple of 4'x4' pieces of drywall. laminate them, and see how hard they are to separate - then decide if delaminating is a concern.
I mounted mine on RC. The first layer is not going anywhere because it's screwed on. The second layer has been on for several years without issue. The wall I tore down and replaced with the current was also laminated in a similar manner and it was pretty much impossible to separate the layers. I wouldn't do a screwless face layer for a ceiling or perhaps a 20' high wall, but an 8' wall is not a life-threatening safety issue.
I don't think it's worth arguing over. Everyone has different levels of experience and comfort levels with construction methods and execution, and so will make different choices based on such.