Control room and "live" room on adjoining joists

Hi all. I'm sorry but I don't have any drawings. I've started building a non-professional recording studio in my basement in the woods. Neighbors aren't a problem but I'm hoping to get some separation between the control room and the "live" room. some specs: cement floor Most of the live room is under ground The control room is 10 by 17 with ceiling height of 8 feet "Live" room is slightly bigger. The "live" room shares a wall with a room we boxed are oil heater in. I'll just turn the heater off when tracking. We floated the ceiling on Hat channel and sic clips and sealed the parameter with sound caulking. We'll do the same in the control room. The two walls separating the "live" room and control room we'll be covered in two layers of sheetrock with green glue in between and two layers of glass different thicknesses. Here's the question, unfortunatly, we couldn't build a room within a room, so we built our separating walls on adjoining joists. There is closed cell rubber between the headers and the joists. So, knowing we did things wrong due to financial and space considerations, would you have any ideas on what to do within this 14 inch space between the walls which will hopefully be our "dead air space"? pics attached Any help would be greatly appreciated, Thanks, Tom

Two things you can do. One is to remove the hard connection with the overhead joist for both walls. The closed cell rubber between them probable is of no use . This is a short circuit area that allows vibration to go from one wall, up into the overhead floor system and back down into the opposite side wall. You can understand how this is defeating your purpose? The other would be to add mass into the overhead cavity of this 14 inch space and then install insulation after that as usually.

Hi Xspace, Thanks for the help. So obviously your first suggestion is a dig, which I deserve for doing this in the first place. There is no way to remove the header from the joist at this point so mass is my friend? If I were to use a green glue sandwich a couple inches below where the header meets the joist and fill it upstairs with rockwool, would that be my best bet? Also, to do this I have to add more contact to between these walls in the pic above the neighboring joists for nailers to put the rock on? I'm trying to make the best of this bad situation.

What xSpace was telling you is not an "either/or" option. It is a "both" option. You need to do BOTH of the things he said, not choose between them!!!

There is no way to remove the header from the joist at this point so mass is my friend?

Well, mass is your friend, but flanking is your enemy! :) And in this case your enemy is going to beat your friend, unfortunately. The war is already lost. Your friend is already defeated, before the battle even starts. Mass will only help up to the point where the flanking path transmits more sound around your mass, than your mass is stopping. Think of it like a leaky roof in a thunderstorm: you can apply all the plastic, sheet metal, tar, tiles, bitumen, sealant, caulk and everything else you can think of, all over the roof, but until you fix the six-inch hole in the middle of the roof, the rain is still going to come in. The rest of the roof might be fantastically sealed (mass), but the hole in the middle is the problem (flanking). Your direct mechanical connection between the two walls (called the "flanking path") is the acoustic equivalent of a six inch hole in your roof. Unless you can fix that, no amount of mass is going to help much, just like no amount of sealing is going to stop the rain coming in with the example of the roof. You have to fix the hole, to stop the rain. You have to break the flanking path to stop the sound. You cannot beat the laws of physics. Not even by wishing them away! I'd seriously consider ways to break that flanking connection, and re-build at least one of those walls, preferably both. If not, then you have put in a lot of effort that is going to go to waste. And you will have to put in even more effort, knowing that it will not bring any useful return. Not to mention the money... What is the reason that prevents you from taking down those walls and re-building them correctly? Time? Money? Pride? Lack of workers to help you? Lack of space to build what you want? There are solutions to all of those... - Stuart -

stelladat wrote:

Hi Xspace, Thanks for the help. So obviously your first suggestion is a dig, which I deserve for doing this in the first place. There is no way to remove the header from the joist at this point so mass is my friend? If I were to use a green glue sandwich a couple inches below where the header meets the joist and fill it upstairs with rockwool, would that be my best bet? Also, to do this I have to add more contact to between these walls in the pic above the neighboring joists for nailers to put the rock on? I'm trying to make the best of this bad situation.

Like Stuart said, it isn't a dig, it is what it is, a hard connection/flanking path. "If I were to use a green glue sandwich a couple inches below where the header meets the joist and fill it upstairs with rockwool, would that be my best bet? " No sir. Apply the mass directly to the plywood sub-floor overhead...NO space. If you cannot or will not remove the connection between the joists and the walls then this is a history lesson for you. I think you can break it[the flanking connection], but then again, I also have a saw-zall. So these little boo-boos don't stop the flow, they just broaden the time frame. After you install mass in this cavity and insulation, you can look into that green glue sandwich thing you mentioned above. But I would add mass to the upper floor first, then insulate...then put in the second leaf you described.

EDIT Reading comprehension: Low

It isn't that complicated really. If I had it to do; I would get a saw-zall with a 10-12 inch aggressive toothed bi-metal type blade placed directly at the connection between the bottom of the upper most plate and the top of the lower plate. Cut it from one end to the other horizontally to release the nails that are binding them together. Safety glasses are a MUST. Once you make that cut you may have to wrestle the top most plate out, but it will come out. Assuming there are no nails going from the >joist< into the top plate. If so, I would cut that loose as well. But I would really have to be in that room to get a better understanding of how this is fabricated from top plate to floor joist. Ymmv,

Boy do I feel like a dummy. We already hung the live room ceiling's sheetrock on hat channel and sic clips,mudded and sanded. It is NOT touching the header of the wall other than by caulking closing the 1/4" gap we left. So, If I remove the one header attached to the joist, the wall will be free standing on the studs and the one bottom (top) header. But, flanking will occur now from the walls. I think at this point, I'm just screwed. I guess I'll live with headphones or buy an iso booth. What about building another free standing wall in the control room like I should have done from the beginning? Thank you all for your help. I'm going to go jump off a cliff now.

I wouldn't go that far. Everyone has, in hind sight, made a mistake that seems like the whole project is going to be ruined. You may find there are times this room is going to be a good build. What you may wind up doing is understanding when you can do some things and when you cannot, based on overhead footfall or noise from just living. if it even becomes an issue.

Just so I understand. You keep referring to "the header". When I look at this wall I am looking at the two(2) 2X4 top plates laying horizontally. The plates attached to the joist...those plates. The header is the 2X6 (or 8 inch) laying across the cripples.

Hi Xspace, Thanks again for spending time on my situation-it is greatly appreciated! I'm doing all this work with a just a friend who dables in carpentry. Before I bought this house a year ago, I never did any building. I do make a living as a location sound mixer. I dabated for months about wether I should keep this basement as an open room or try to get some isolation. Although it is far away in the Adirondacks and surrounded by acres of woods, I do have one neighbor across the street. So, I was always planning on doing some building to keep some sound out so I could play drums or guitar and any hour of the night and no one could hear- a dream I've had since I was 12. So then, I decided it would be nice to try and make the space more like a studio with two rooms and isolation in between. I will have to download sketchup and learn it so you could see the entire build. I have been incorrectly refering to the top plates (the 2x4's attached to the joists) as headers if headers are the top of the window frame, the 2 x 6's- or a door. Can I ask a question that I haven't seen in my research because maybe it's such a simple question that people overlook it? If I were to take out the top 2x4 of one wall, the one in the control room that does not have the hat channel on it yet, the wall would be free standing? If you can't attach the "top plate" to the joist that what do you attach it to? Is it strong enough to hold up all the weight? I can't wrap my brain around this. Even if I were to introduce another 2x12 joist in between the existing ones, would it not have to rest or be screwed to something that alraedy exists to hold it into place? Also, if I remove this upper 2x4 top plate, what would i put in it's place? Thanks again. Again, this isn't a professional studio so i can handle some sound coming through I'm just trying to make the best of an aweful situation to record in. Thanks Xspace! Tom

This is a resilient connection made from a wall top to a floor joist. download/file.php?id=2079 (taken from Aaronw's thread) Here is the part of the thread on how Aaron designed and fabricated his sway braces. Here is a description of how to keep the "air" of the two areas separate.

Just a quick question- what about the walls that are running perpendicular to the joists? I'm going to assume that you connected those to the joists as well.... I'm concerned about your walls having flanking from the floor above when asking this question. Maybe I'm just introducing another "point of panic" into an already completed equation, but thought it should be addressed at least. Thanks, Andy EDIT: sorry, should have looked (and read) more closely. I now realize that you were building only two walls to separate the rooms.

Hi Xspace and all, Just spent several hours removing the top plate attached to the joists. I used metal saws all for the nails, removed all the caulking and moved the side studs up against the walls in a 1/4 inch. I secured the top plate, 1 2x4 with SIC's isoation clips on hat channel. Now there is no contact between the walls at all except for the shared concrete floor. The walls seems plenty strong enough for the two layers of rock with green glue and the two diameter windows, 3/8th and 1/4 inch. I don't know why I didn't do this from the start. So now I've got a 1 inch gap above the hat channel and the joists running parallel. So thanks for saving this project before it was too late! I made a small donation to the forum because this really was a critical mistake. Now, I'm confused as too what to fill this 1 inch gap with, and I'm also back to my original question about how to seal and fill this now decoupled 14" space between wall. You had suggested before to put mass right up against the plywood subfloor. If this mass was a green glue sandwich, should it be screwed into the subfloor or should it not touch either of the joists? -leaving a 1/4' inch on the sides? Is 3" rockwool a good choice between studs in both walls? Thanks again, Tom

You want to do the mass addition directly to the overhead subfloor. I wouldn't screw it into the subfloor, instead, use a 1X2 or 2X2 cleat and press this material up against the drywall in the overhead cavity, then screw the 1X2 cleat[or 2X2, which ever you have] to the joist(s) to support the rock. Caulk the connections that the cleat makes with the joist AND the drywall. Add insulation into the cavity. Then I would install another set of cleats as described above, only have them raised above the bottom most part of the floor joist enough to install 2(two) more layers of rock. It's kind of a two fer, maybe a three fer. This makes a mass/air/mass between your upper and lower area. It also closes the open ceiling line so that this is not a weak spot in the event of fire. Yes, I said it, fire :) "I've got a 1 inch gap above the hat channel and the joists running parallel. " I would actually have to see a pic of that to get my head around what it is you are saying verses what I may think it to be. Thanks and good luck, Brien "show me the money next time" Holcombe :)

Thanks Xspace. I'll send you a picture of the 1 inch space as soon as I can. Again, greatly appreciate your advice, Thanks :) Tom

Hi Brien, I've finally found some time to continue working on this basement studio "experiment". If you have any time at all, I'd love to pick your brain a little. Most of the the pics in this thread still apply, but we removed the top plates attached to the joists and put in hat channel with sound iso clips. I've uploaded some close ups of this. You had mentioned stuffing the area between and above the walls aka joists (between 2 joists) with mass and attaching with cleats. Could that mass be 2 layers of rock with green glue in between, cut to fit 15"? Would this be fit snugly touching the joists or should there be a 1/4" gap on each side that could be caulked? Then I would put up cut 4" thick rockwool up against that or air before the rockwool? Thanks again, Tom in Lake Placid.