Taking the advice of a local HT friend, I've invested in some of the DC04 clips to decouple my walls from the joists for my basement theater.

To that end, I've seen a couple different methods of mounting the clips on the forum, but the only recommendation I've seen from the manufacturer is as below:



with 3 clips supporting each stud (I guess they want to sell clips).

Here is a drawing I did representing one mounting style, with green arrows being the mounting screws. In this method, it seems similar to the standard hammering a nail vertically into a ceiling joist. The shaft of the screw takes care of lateral (side to side) movement of the wall and several screws are into the flat side of the clip to attach to the wall.

In the second method, the DC04 clip is mounted "sideways". The flat side is screwed into the joist and the rubber isolator is attached to the side of the wall with one screw.



I'm not a civil engineer or anything, but it seems like a potential concern regarding the lateral load on the wall - ie if someone pushes against it, there is only one screw holding the wall up per clip.


I am curious what the more structural knowledgable folks think about this, and what building inspectors have had to say. It would be much easier if PAC offered acceptable alternatives, but without approved drawings from them I wonder if there are improper mounting methods to use?

I don't have an answer for you, but I would like to know where to get a few of those clips to experiment with. I may be ignorant, but I don't see how these are beneficial to isolating sound, by decoupling. You have a metal bracket with rubber grommets, and a screw that gets tightened down through the middle? Is this just to keep the wall from vibrating? I guess I'm thinking if you put a screw in a floor joist and smack it with a hammer, you hear it upstairs, right? O.K., same screw, with rubber on it, what's the difference. I think there is still a transfer of sound through the screw no matter what. Like I said I may be ignorant, and I defiantly don't intend to ruffle any feathers. Scott

Are you using RSIC, hat channel, and drywall on the ceiling on both sides of the wall? If so the ceiling drywall will be more than adequate to hold the wall laterally in place and I would use the minimum number of DC-04 needed to stabilize the wall during the construction process.

Like this...

http://home.comcast.net/~scottj0007/theater/empire_wall.jpg

I don't have an answer for you, but I would like to know where to get a few of those clips to experiment with. I may be ignorant, but I don't see how these are beneficial to isolating sound, by decoupling. You have a metal bracket with rubber grommets, and a screw that gets tightened down through the middle? Is this just to keep the wall from vibrating? I guess I'm thinking if you put a screw in a floor joist and smack it with a hammer, you hear it upstairs, right? O.K., same screw, with rubber on it, what's the difference. I think there is still a transfer of sound through the screw no matter what. Like I said I may be ignorant, and I defiantly don't intend to ruffle any feathers. Scott
ScottJohnson,
The pac-international resilient sound isolation clips (RSIC) have been independently tested to be very effective in sound isolation. See this link (http://www.pac-intl.com/tests_wl_wood.html) for some of the test results. Almost all of the professional theater designers who are on this forum use or recommend them where appropriate. I used them, along with GreenGlue, in my construction and I have to say that I am amazed at how well the combination works!

- ScottJ (another "scott")

What PAC doesn't show in any of their drawings (but I have confirmed via an email which I can't find right now) is to build the wall in the standard way, but about a 1/4 to 1/2 inch short. Stand the wall up and mount the clip with the grommet attached through the top plate of the wall and the metal part attached to the side of the joist. I used about three per standard 8 foot wall section (never less, sometimes more if it looked like it needed it).

I found working alone that the easiest way is to MEASURE (then measure again, then measure again), then make the first cut. Then lay the top and bottom plates on the floor under the joists the wall will be under. Take the cut piece and place it on top of the two plates and under each of the joists to check the measurement. THEN make all of the cuts for the studs for the wall section. Nail the wall together (which is the fast and easy part with a framing nailer) and stand it up in place. Run a long, coarse deck screw through the top plate into a joist in about the center of the wall. The wall should stand by itself now. Square the bottom plate and run a couple of screws through the bottom plate (I have a dricore floor so I have the luxury of moving things around later if I have to). Then go back up top, loosen the screw and plumb the wall and run the screw back in so the wall is plumb. Then attach the RSIC clips.

I found that it is pretty easy to lay the clip on the topplate so that the metal side is touching the side of the joist, then using a drill with the right size bit (as big as the whole in the gormmet (I forget right off hand the size but the whole ends up a little larger then the diameter of the screw), eyeball it from the bottom of the topplate and drill up through. Drop a 1/4" 4" long lag bolt with a washer in from the top and then a washer, lock washer and nut on the bottom and tighten up.

THEN REMEMBER TO REMOVE ANY SCREWS THAT YOU'VE RUN THROUGH THE TOPPLATE INTO THE JOISTS, or you defeat the whole purpose!

Good luck,
Tom

Empire,

I am still building mine, but I have finished 3 of my 4 double walls and used the 2nd method.
As explained to me by Bryan (bpape), you want to understand which way the wall would move under the load (sound waves here), and put the rubber section aligned to absorb that motion. As in your second drawing.
I will try and get a photo and post it.

ScottJohnson- big difference between hitting a screw with a hammer (Impact load) vs such a small surface to absorb the vibration from sound, especially when that screw is shielded by 2 sheets of drywall/GG.

Paul

O.K. now i see how it would work wit the rubber grommet on the wall and not the floor joists.

tlogan---good description.

I don't have an answer for you, but I would like to know where to get a few of those clips to experiment with. I may be ignorant, but I don't see how these are beneficial to isolating sound, by decoupling. You have a metal bracket with rubber grommets, and a screw that gets tightened down through the middle? Is this just to keep the wall from vibrating? I guess I'm thinking if you put a screw in a floor joist and smack it with a hammer, you hear it upstairs, right? O.K., same screw, with rubber on it, what's the difference. I think there is still a transfer of sound through the screw no matter what. Like I said I may be ignorant, and I defiantly don't intend to ruffle any feathers. Scott

You can buy them from Bpape. I bought 8 to mount my 2 garage doors in my new house, and it did help to quiet them down. You can still hear them, but not near as much.

Thanks for the insight guys, that definitely helps me better understand.

To answer the question of where to purchase them, first here is the manufacturer's website PAC International (http://www.pac-intl.com/decoupled.htm)


I purchased mine over the internet from Professional Acoustics Co (http://www.professionalacousticsco.com/)

They got the clips to me from the west coast in about a week.

Armyman, I see your (and Bpapes) point about aligning the rubber grommet like a spring action to damp out the sound vibration. I wonder though why PAC shows their standard mounting then as mounting the clip vertically (as in figure 1)? Sitting here playing with the RSIC clip it seems like it has more "springiness" moving the rubber grommet side to side rather than up and down. Using the method you employed however has a distinct advantage (for me at least) of connecting my wall offset from the joist without installing blocking between my top joists.

Tom,
Thanks for the detailed explanation. It sounds like the method you employed is the most robust utilizing lag bolts to hold it all together. Was you email from PAC I guess?

ScottJ0007,
Excellent point on the holding effects of the drywall, I hadn't considered that.


Has anyone run into trouble with the framing inspector on the "wrong" way to install these?

And don't get me wrong, I am not passing judgement on anyone's installations, just trying to compare the pros and cons. This is why engineers never finish anything, we are always overanalyzing things to death first!

For what it’s worth, I’ve actually used all of these installation methods in my room. Different spots in the room (paralell to floor joist vs. perpendicular) and various obstacles in the way necessitated different installation techniques. So far, they all seem fairly equivalent.

Has anyone run into trouble with the framing inspector on the "wrong" way to install these?

I'll let you know when I have the inspection. I'm doing electrical now. :)

I don't know if it's right or wrong but I did pretty much the same thing as Tom, spaced the clips every 4 feet. Walls feel pretty solid.

Andy

I'll let you know when I have the inspection. I'm doing electrical now. :)

I don't know if it's right or wrong but I did pretty much the same thing as Tom, spaced the clips every 4 feet. Walls feel pretty solid.

Andy

Sounds good. Considering I am (ahem) side stepping the whole permit thing, if your inspector is happy, then the mounting style must be ok.

Tom,
Thanks for the detailed explanation. It sounds like the method you employed is the most robust utilizing lag bolts to hold it all together. Was you email from PAC I guess?


Yes. As an FYI, I STILL can't found the actual email, but I HAD referenced in a now archived post if you are interested:

http://archive2.avsforum.com/avs-vb/showthread.php?t=521860&page=2&pp=30

Tom

Armyman, I see your (and Bpapes) point about aligning the rubber grommet like a spring action to damp out the sound vibration. I wonder though why PAC shows their standard mounting then as mounting the clip vertically (as in figure 1)? Sitting here playing with the RSIC clip it seems like it has more "springiness" moving the rubber grommet side to side rather than up and down. Using the method you employed however has a distinct advantage (for me at least) of connecting my wall offset from the joist without installing blocking between my top joists.


I think you just answered your question in that statement. The extra "springiness" in the side-to-side motion translates to extra energy dissipation in shear than in compression. Hence, they show that particular installation detail.

Hi everyone,
I have some updates... I contacted PAC international through their website, and they are extremely helpful, they got back to me in less than an hour.

I sent them the first method diagram and responds excerpted as follows:

"The 36 pound design load is for Pull and Shear.

However, in you application, as I understand it, the loads which you are applying are lateral loads. These loads are functionally fail safe Steel to Steel with a rubber isolator.

Assuming you use a #14 x 2.5" Minimum Fasteners to attach the RSIC-DC04 to the joist with Predrilled mounting holes in to the joist to avoid splitting the joist. You will have no trouble with placing the RSIC-DC04 at 24" center to center or less. Be sure to stagger the RSIC-DC04 from side to side to create a balanced installation.

If you are based in California or any of the western states you have a earth quake (dynamic) safety margin you should add into your design which would be to place the RSIC-DC04 on each side of the wall every 24" for safety.

"

Also, regarding fastening the steel plate to the side of the wall:

"I would use #10 x 1-1/4 to 1-1/2" long. Preferably NOT drywall screws. Four per RSIC-DC04 will provide more than enough hold for your application as I understand it."


So, I will be installing using method 1 probably every 24", with #14 x 2.5" wood screws through the rubber grommet into predrilled holes in the joist, and #10 x 1/2" wood screws to attach the side plates to the side of the wall.

I should also install clips on either side of the 2x6 stagger stud wall to balance, but I don't have a joist on that side to attach to. I may put in blocks between joists to attach to that side, so all the RSIC clips are not all on one side of the wall.

I'll post photos when completed as another possible method for forumites to use that "seems" to be approved.

Dave