John Sayers' Recording Studio Design Forum Archive

On page 116-117 of the USG Construction Handbook,

http://www.usg.com/Expert_Advice/Constr ... en)_03.pdf
(845kb)
it says...

At inside vertical angles, only the overlapping base layer should be attached to the framing to provide a floating corner.
Omit all face-layer fasteners within 8" of vertical angles.

• 1. Does that mean that sheet A is not attached to the stud (or any framework) in the corner and is held in place only by sheet B?
  
  2. What might be the acoustic advantages of a "floating corner"?
  
  3. Why would they say to "omit all face-layer fasteners within 8" of vertical angles". I don't understand the thinking behind this suggestion either.

I'm building a two layer wall, direct fixed to the stud (no RC) and am trying to get clear on the various fastening options.

Most other sheetrock manufacturers suggest fastening around all outside edges and in the field of the sheet.

USG is the only manufacturer (I can find) who suggests the above methods

Any thoughts on this appreciated.

Dave

Dave, I'm gonna have to think about this a bit - first, are you saying you're building a single framed wall and NOT using anything to decouple one side from the other? If so, why? What is the application? Steve

My problem is the reverse of most people here - I'm trying to keep noise out.

The house is a small 1960's timber framed cottage, good location - 200 yards from the beach and surrounded by trees - but it's become very noisy in recent years.

There's a main road about 50 yards away that gets busier each year and my nearest neighbour has turned into a hell man - added a big deck right near my house, a new dog with a big woof and a thumping new stereo - he likes to party hard.

I've been researching this whole acoustic building thing for about five months now and tied my brain in a knot so many times I've lost count.

Man, I was so relieved when I found this forum - thought I was the only one grappling with all these different standards, minutiae construction details and conflicting information from different suppliers.

Regarding RC v direct fixing, I seriously considered RC for this room and bought a length to get familar with it. The room has three exterior walls and a low slope metal roof. After listening to all the different types of noise coming into the room, the ceiling is the main source of the most disruptive noise - the neighbour's place - which sits higher than mine. The three exterior walls get the traffic noise.

So for the ceiling I'm using rubber isolation (resilient) mounts to suspend furring channel and fixing two layers onto the furring channel with 125mm of insulation in between the new lower ceiling and the metal roof.

This is what the mounts look like...




According to the test results, these mounts increase STC ratings by about 5 points. This is the supplier of the mounts http://www.gyprock.com.au (The "System Selector" on their site is a good source of tested wall systems and there's masses of PDF's with construction information.)

Getting back to the exterior walls, I'm aiming for an STC of about 45 - more would be good - but I think that will take the edge of the traffic noise.

The interior wall (which faces the neighbour) is getting the same treatment to deal with noise which comes through the roof and any open windows in other parts of the house.

The cavity bewteen the wall studs, I've filled with 75mm Rockwool and am planning to direct fix 2 layers of different types of materials - one layer of 1/4" (6mm) fibre cement (10kg/sq mtr) plus one layer of 5/8" (16mm) fire plasterboard (or sheetrock) (12.5kg/sq mtr).

I'm not sure what you guys call fibre cement in the U.S. but there's info about it here http://www.csrfibrecement.com.au.

Test results for this fibre cement/sheetrock combination are the same or better than a straight sheetrock/sheetrock combination. It also helps keep the wall thickness down which saves me having to move the door, deal with an even smaller room and various other issues.

Here's a sample of test results for this wall system.

(The link had to be cut into three lines to avoid horizontal scrolling in this thread. Copy and paste each line into your browser address window so they make one long link.)
Windows are being upgraded to match with a double window of 6mm and 4mm glass and an 80mm air gap. I've also built an 8ft air duct (with similar insulated walls and insulated ducting) on the side of the house to bring air in fresh air.

Hi, welcome to the board (and the "I hate noisy/bitchy neighbors" club...)

Since sound isolation is a two-way street, the same techniques apply whether you're trying to keep it out or in -

The sound clips and channel are as good or better decoupling as Resilient Channel. You still need to terminate channels about 1" away from adjoining surfaces so you don't couple them, for best flanking noise control.

The fibrecement stuff sounds like the oz version of "wonder-board", basically fiberglass-reinforced concrete of sorts. They show in their PDF using it for the exact same applications; more mass than gypsum per unit thickness but (here, anyway) also more expensive. Also a bit more difficult to work with in some ways.

Are you saying that your roof right now is just bare metal, and that you intend to make only one 2-layer inner addition and then fill the gap with insulation? If so, we REALLY need to discuss this to death.

Window plans sound fine, probable weak link here would be one-piece framing from inside to outside with no decoupling of surfaces.

8 feet of duct, even heavy walled and lined properly, may not be enough to attenuate sound - would this be straight, or with a couple of bends included?

If the neighbor-from-hell is really into subwoofers, you might need a full-on room-in-a-room construction to get the lows under control - all that bass, since it's pretty non-directional, could be invading from any and ALL directions. Once it gets into your structural frame, only resilient decoupling will help much.

Not trying to make you wanna slit your wrists, just letting you know this may take a bit of work - but it can be done, so let's get started... Steve

OK let's start with the ceiling...

Are you saying that your roof right now is just bare metal, and that you intend to make only one 2-layer inner addition and then fill the gap with insulation? If so, we REALLY need to discuss this to death.

Yes.. that's right. Here's some test results from a similar system but without the resilient mounts.



Test results from here...

(The link had to be cut into three lines to avoid horizontal scrolling in this thread. Copy and paste each line into your browser address window so they make one long link.)
Must admit I find this test result hard to reconcile with the reality of listening to the bare metal roof - it sounds like it has an STC of about 15-20. The old internal lining was just one layer of 3/32" (4.5mm) fibre cement fixed 2" (50mm) away from the metal. That sounded like an STC of about 25-30. (...wish I had a sound meter).

So according to this test result, the extra mass and what looks like about a 6"-8" gap, produces an extra 15-20 STC points.

Currently I plan to lower the ceiling by about 4-1/2". The ceiling panels sit bewteen 6" exposed timber beams. I experimented with lowering the new internal lining to the underside of the beams (fixed one sheet up there temporarily), but it felt too low.

So that's how I got to the current ceiling plan.

The 80mm window gap was arrived at with the help of this page http://irc.nrc-cnrc.gc.ca/cbd/cbd240e.html ...and this diagram.



Re the duct, It has two 90 deg bends at the moment. But on the inside of the room, I plan to fit a "muffler" box (yet to be designed). I think the technical name for them is "plenum chamber".

btw... what have I posted in this thread that creates the need to scroll horizontally?

To try and answer your original post questions, first of all, the quote is from LAMINATING two sheets together.

The inner sheet is only attached in the corner on one side only to stop flanking betwen the two walls.

Same reason for floating the corner.

The outer sheet is still held in place by the glue.

In the figure you copied you identified base layers on both walls as A and B. The base layer is the first layer.


I hope this helps.

Andre

Your comments have helped Andre... it's coming clearer.

Here's how I now understand it.

1. Both base layers (A and B in the above diagram) get fastened as if they were single layers.

2. Then the top layers are fastened using

• - adhesive applied in vertical strips to the vertical edges and field of the sheet
  - screws/nails along the vertical edge that is NOT in the corner
  - screws/nails along the top and bottom horizontal edges EXCEPT not within 8" of the corner.

Is that right?

If so, I'm still confused by the phrase "overlapping base layer" (7th line below)

And I still don't understand the acoustical advantages of having the top layer "floating" in the corners.

Here's the relevant section from pgs 116-117 of the USG Construction Handbook...

Double-Layer Adhesive Lamination

In multilayer adhesive systems, the base layer must be attached with the same fastener, fastener spacing, and framing spacing as for a single-layer assembly of the same thickness as the base layer.

In fire-rated assemblies, permanent fasteners and the type of board used must be the same as in the particular tested assembly (see specific design for complete description).

Application of the base layer may have long edges either parallel or perpendicular to the framing. Plan the layout of the face layer so that all joints are offset a minimum of 10" from parallel base-layer joints. It is preferable to apply the face layer perpendicular to the base layer. At inside vertical angles, only the overlapping base layer should be attached to the framing to provide a floating corner. Omit all face-layer fasteners within 8" of vertical angles.

Apply laminating adhesive in strips to center and along both edges of laminating face layer board. Apply strips with a notched metal spreader having four 1/4"x1/4" minimum notches spaced max. of 2" o.c.

Position face layer against base layer; fasten at top and bottom (vertical application) as required. For laminated ceilings, space fasteners 16" o.c. along edges and ends, with one permanent field fastener per framing member installed at mid-width of board. Press board into place with firm pressure to insure bond; reimpact within 24 hr. if necessary.

The scrolling problem is caused by the long, unbroken links - I think there's a way to defeat that by breaking them, but don't know how.

The method you're referring to is for LAMINATED multilayer construction, which is NOT the most effective way for sound control. You get better isolation by letting each layer act as its own mass. Also, gluing drywall can get tricky especially if you use laminating type screws (Type G) - if you wait too long, the glue can soften the panels and cause failure of the laminating screws. Because of that, we've recommended NOT to use this method.

Leaving panels floating near joints is done so that intersecting walls don't excite each other and degrade isolation - they still need to be sealed, which is done by leaving 1/4" gaps and sealing with heavy acoustic caulk/sealant. For multi-layer, you stop any reslilent mounts about 1" away from intersections and fasten to the resilient mounts within 4-8 inches from the intersection. I prefer to alternate layers; in the case of a "south-east" corner, you would put up a south layer, then an east layer and caulk, then a south layer, caulk, east layer, caulk - if you like, one of the newer flexible plastic "inside corner" beads can be used before finishing - just don't put too much mud into corners as it will slightly lessen isolation.

If you're mounting direct to studs on both sides of a single stud frame, isolation will be at least 6-7 dB worse STC than if you use resilient mounts; however, the TL at lower frequencies is mainly affected by mass-air-mass, so won't change with or without resilient mounts (or even separate frames) unless you add mass or increase the air gap.

Can you post a drawing of the exact wall construction you're planning, so we can understand what you need? Thanks... Steve

Steve, thanks for your advice... so laminating is not the way to go.

The pic below is exactly the problem I'm trying to solve - what is the best way to attach the internal face layer in a corner where the framework was designed for a single layer and the stud is too narrow for two layers?

This thread http://www.johnlsayers.com/phpBB2/viewtopic.php?t=598 ... describes how to fix two layers where there IS sufficient room on the stud to fix both layers using screws or nails.

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.

The reason this USG laminated "floating corner" idea caught my attention was because of

• - the overlapping corners (as per your south-east corner example)
  - the fact that it solved the problem of not having enough room on one stud to attach the face layer with screws/nails.
  - the implied acoustic benefits of a "floating corner"

So, if there isn't enough room on the corner stud to screw/nail the face layer to the stud, what's the best way to solve this problem?

Attach a batten to the stud to make it wider?... or screw the face layer to the base layer with laminating screws?... or let it "float" in the corner (no screws or nails) as per USG's idea?

Dave

ps... tried breaking those long links in half but scrolling still there.

Battens are probably the most durable way to do this; or, if the next stud is less than a foot away you can float the corner, caulking as you go and using plastic flexible inside corner bead. Laminating screws/glue would be my LAST choice.

I'm still wondering what the OTHER side of this frame has on it, and if you're doing anything to decouple the two leaves of that wall or not can you expand on that drawing to show what the other side of the frame will have attached to it? Thanks... Steve

On the other side of the wall frames is the exterior cladding - a 5/16" (7.5mm) fibre cement product which looks like timber boards. To do anything with the outside, I'd have to change this cladding - a major production - and part of the house would look different to the rest as you can't buy matching cladding anymore.

The other thing is that the noise that comes through the walls is the woosh-woosh of cars and occassional rumble of a truck. I'm guessing an STC of around 45 will take the edge of ths.

The really disturbing noise from the neighbour comes through the ceiling. So I figure it's the ceiling that needs the de-coupling treatment (see above).

Dave

ps... finally got rid of that horizontal scrolling problem... had to cut the long links into three sections.

I just looked up the Austrailian data for those Gyprock Resilient Mounts you intend to use, and it looks like they may be a good potential solution in my upcomming rebuild. I had looked at some of the Kinetics solutions, but they we just too pricey for us.

Searching on Google only leads to Austrailian based sites and suppliers, so I have no clue what these mounts actually cost, or where in Canada or the US we might find a supplier.

Anyone out there know who might sell these on my side of the pond, and/or what they cost???


- Ron Charles

In Australia, they cost A$3.50 each (plus 10% local tax if you live in Australia).

You could try contacting them via their contact page to see if they have a U.S. office. You'd need to be able to purchase the matching furring channel (Rondo #308 which the mount is designed to grip) in order for it to be a fully working solution.

Rondo is the manufacturer of the furring channel and I think they also may make the resilient mounts for CSR. The lot I purchased came in a plastic bag marked "Rondo".

http://www.rondo.com.au/rondo/

They may have international offices.

Have you checked out these people's mounts?

http://www.pac-intl.com/home.html

Frustration rant: how can we help you with suppliers in your area if you don't even fill in the location in your profile? Read the stickies at the top of the forum!

Searching on Google only leads to Austrailian based sites and suppliers, so I have no clue what these mounts actually cost, or where in Canada or the US we might find a supplier.

I assume you are looking for the Canadain supplier.

Company: Soundtrap
Phone: 705-357-1067
FAX: 705-357-2689
Toll Free: 888-502-1958
Address: 9 Doble Street
City: Sunderland
Country: CANADA
Zip: L0C-1H0
Contact: Roger Foulds


The Canadian supplier was just changed. Before, the price was $7.00 a piece. With Soundtrap it is $10.00. You might want to try Auralex Canadian dealers. Auralex lists them for about $5.00 US on their website.

Kinetics makes a competitive product: Isomax isolation clip: DISC. I seem to recall the Canadian price is around $7.50.