Hello everyone...
I'm reading the "sticky" written by you Steve, about applying multiple layers of sheetrock to a wooden frame. here's the quote:
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. 5A - replaces 5, above -
Fastening a second layer of wallboard to a first layer, when the first layer is mounted on WOOD studs: First, if building a SINGLE frame with wallboard on both sides, it's STRONGLY recommended to use Resilient Channel on ONE of the sides of the frame – otherwise, you lose several dB of isolation at mid and higher frequencies (above 100 hZ typically) – follow the rules for mounting wallboard to RC on this side – no screws in line with studs so you don't accidentally "short out" the RC.
Fastening a second layer when there is NOT RC under, the most practical way is to mount the first layer using half as many screws as normal, same with any following layers EXCEPT
the outer layer – this one should have full fastening schedule used, and with long enough screws to penetrate all layers and solidly fasten to the studs.
now, this one really throws me off. Is this the valid statement, or is there another update of this procedure??The shortening of all the layers and into the studs just doesn't sink...please help
Thanks Steve...
If I read it correclty, he is advocating (on a single wall construction) fastening the direct layer(s) to the studs and fastening the other layer(s) to the RC.
So you end up with one side of the wall affixed to the studs and the other side affixed to the RC
Giles is right about a single frame, RC one side wall system.
Originally, I had thought that ANY fastener that penetrated all layers AND wood studs would be a problem, and that would be true if both leaves of the wall were solidly mounted to the SAME studs - to a lesser degree, same with single frame, staggered stud walls.
Because of that, I had followed my interpretation of the USG handbook, which (to me) sounds like it's OK for walls (not ceilings) to use strip lamination and Type G laminating screws for face layers on sound walls. I STILL think that's what the USG handbook means.
However, Rod Gervais (who has built things I can only DREAM of) contends that the Type G fasteners are only temporary, and does NOT recommend using this method - he is concerned about glue not being strong enough NOT to cause premature wall failure.
This isn't over as far as I'm concerned, and I intend to have another phone conversation with Rod over just this subject, with both of us reading and discussing the same laminating section of the USG manual during the conversation.
I was told (by either Rod, Eric, or Wes Lachot, don't remember) that any flanking caused by penetrating all layers would be mostly eliminated by the insulation fill - the recommended method in that case is half as many screws as normal for all under layers, then full schedule for the face layer.
Bottom line is this: If you build walls before this is settled, I would stick with separate frames, or at least RC on one side. Either method negates the worry about flanking through fasteners, because of the isolation gained with separate or resilient decoupling of the two leaves of the wall.
Once this is settled between Rod and me, I will (again) edit that admittedly confusing section, and alert everyone to the fact... Steve
Is there a diagrham of the procedure on the USG site or can you get one posted when you get the final word ?
I am also ready to start building some walls and this is going to affect what I do .
Jim
Page 117-119 of the USG manual, linked in the Construction forum - it's the bottom "sticky" - if you want detail, go for the high res version (21.63 MB)
BTW, what type walls are you doing where this would affect them? Steve
Hi Steve,
I had just posted over on RO about this very topic...(again, nice to see this site is up again...hope it stays up better now.)
So, I have two separate wall frames, the one in the iso is floated (as per your instruction-thanx!), the other wall, which is inside the control room, has RC...so, that being the case, you think its ok to screw the 2nd layer of drywall in the iso booth directly through the first and into the studs? This is my understanding of this according to the post above.
So, I have two separate wall frames, the one in the iso is floated (as per your instruction-thanx!), the other wall, which is inside the control room, has RC...so, that being the case, you think its ok to screw the 2nd layer of drywall in the iso booth directly through the first and into the studs?
Am I reading this correctly? You two sets of (I assume 2x4") frames, one of which is floated to make one wall?
If this is the case, the RC on either wall will make the isolation worse.
"If this is the case, the RC on either wall will make the isolation worse." -
Andre, I thought I'd seen something to that effect also but don't remember where - got a source?
Dean, I still need to get with Rod and discuss this live - hopefully in the next day or two. Meantime, if you already have wallboard fastened on the RC side, just make sure your insulation presses somewhat firmly against the panels (if you're using standard house type fiberglass batts, fill the entire area between leaves) - using fasteners through the double layer on the second side won't hurt anything, and it's not worth taking the chance of not doing the strip lamination thing correctly.
As I interpret the USG manual (pages 118-123 IIRC) it's OK to use strip lamination/type G screws, but you need to use regular fasteners into the framing across the ENDS of each panel, no further apart than 24" - this method is NOT recommended by USG for ceilings, period. Rod has said he does NOT recommend this even with walls, but I think he mis-read the USG manual in that section, it's a bit ambiguous there for sure. This is the main area of confusion, and after I talk with Rod again I hope to clear it up. He's built a few thousand more walls than I have so I would tend to go with whatever he says after our talk.
Now I'm really CONFUSED!!! When laminating two layers of 5/8's sheetrock on a wood stud wall AND on wooden truss ceilings, are we to laminate WITH drywall compound and Type G screws WITHOUT SCREWING TO THE STUDS and TRUSSES only to the first layer of drywall, or are we to SCREW TO THE STUDS?? In my case NO RC is being used.
Later this week I'm planning to start the second layer, I concerned that it won't be done properly!!!
Andre, I thought I'd seen something to that effect also but don't remember where - got a source?
I don't remember any specific reference, which is frustrating. The theory is that once you get to a certain point in isolation (in this case, provided b the double stud walls, with one wall floated), the RC separates the Wall board from the studs, which would add additional mass to the leaf.
I hope that last sentence made sense. It reads to me like a perfect example of run on sentences. Unfortunately I can not think of a better way to write it without writing a short essay.
Tom, under NO conditions should CEILINGS be put up without screws through ALL layers and into framing, period. This is probably the ONLY non-ambiguous part of the USG manual.
How are you achieving a 2-leaf system for your ceiling?
As to walls, can you tell us exact construction details from one side to the other? Better yet, a drawing - you're saying no RC, so what framing plan? single, staggered, double, double staggered, wood, steel, ??!?
Good, not a problem - your inner layer(s) can be reduced fastener schedule (typical schedule is shown in the USG manual, download it if you haven't already) and the face layer must be full schedule. Flanking won't be a problem, because you will have insulation in the cavities and separate frames for isolation... Steve
I'm still somewhat confused. Let me see if I've got it straight.
Ceilings... screws through both layers of drywall INTO the rafters(trusses).
Walls...... screws through both layers of drywall INTO the studs.
Now do I use Type G or regular drywall screws long enough for 2 layers, with at least 3/8 of an inch into the wood?
For several months while doing all the other work necessary to get to the point of drywalling, I was sure I had this all correct, glad I caught this before the second layer is started!
