Walls Against Concrete Walls - Proper Construction?

[BradJacob]

What is the proper way to construct walls that are against a basement's concrete walls?

The control room has splayed walls - is it acceptable for these to be the ONLY walls against concrete?

Is the double 5/8 rock on metal studs (stuffed with 3-4" mieral wool) ok for control room and live room walls?

Thanks,

- Brad

[AVare]

What is the proper way to construct walls that are against a basement's concrete walls?

The control room has splayed walls - is it acceptable for these to be the ONLY walls against concrete?

Without more detail it is impossible to give an accurate answer to what you are asking.

Walls between spaces that are to be acoustically isolated are usually built of two layers that are as independent of each other as possible. Having wall layers NOT against the concrete, or connected in any way to the concrete is the optimum. So this brings up the first question: What do you mean by "walls against concrete?"

Is the double 5/8 rock on metal studs (stuffed with 3-4" mieral wool) ok for control room and live room walls?

All that we have to work with is what you write.

The above sentence implies double wallboard on one side and open mineral wool/studs on the other. Although it is quite safe to assume that that is not what you meant, we have no idea what exactly you are meaning. It could vary from, working from one side of a wall to the other:

double layer 5/8" gypsum board
metal studs (25 gauge) on 16" centers
mineral wool (2.5 lb/ft^3) between studs
double layer 5/8" gypsum board

to

double layer 5/8" mineral based board
metal studs (22 gauge) on 24" centers
mineral wool (8.0lb/ft^3) between studs
air space of unknown size
metal studs (22 gauge) on 24" centers
mineral wool (8.0lb/ft^3) between studs
double layer 5/8" mineral based board

All the variable between the two constructions have an effect on the sound isolation. One of the variables is the type of wall board. When posting it may take a moment longer, but try to as detailed as possible and avoid short terms. That is why both of the above walls have boards can be called "rock." Specificity required.

Looking forward to your posts!
Andre

[Aaronw]

Here's a good reference about walls and basements:

http://www.buildingscience.com/resource ... ystems.pdf

Also, take a look through my thread. I have several things here beside floors. There's wall construction, etc. I constructed my walls w/ Steel Studs.

http://johnlsayers.com/phpBB2/viewtopic.php?t=839

Also look at the complete section:

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=598


Aaron

[BradJacob]

Without more detail it is impossible to give an accurate answer to what you are asking.

Andre,

Here is more detail: I think I left out just 1 or 2 details:

1. Walls against concrete means this: There are going to be two walls in my control room that are going to be constructed that will face the outter concrete walls in my basement. The SPACE BETWEEN the control room walls and the basement walls is going to be about 3". So, they're not litterally going to be against the concrete walls or even touching them.

The above sentence implies double wallboard on one side and open mineral wool/studs on the other. Although it is quite safe to assume that that is not what you meant, we have no idea what exactly you are meaning. It could vary from, working from one side of a wall to the other:

...I meant just what I wrote - 2 layers of 5/8 rock screwed to 3 & 5/8 metal studs (16 Inch-On-Center) stuffed with 3-4" of mineral wool.
My question was if this was an acceptable way of constructing a wall that sits "against" the concrete walls. And being that you can't really get behind the other side to install the rock (on the side that faces the concrete walls), I wanted to know if I get away with not doing that - being that there will be concrete walls on the other side. I know that you can build the whole on the floor and then raise it up - but again, I want to know if I can get around this?

Sorry for the confusion. Does this help any?

I do appreciate all your help.

[BradJacob]

Here's a good reference about walls and basements:
Aaron

Aaron,

You've been really helpful in responding to my questions. I have a few before I get started. I 've been reading through the threads (my God - SO many....) and think I have a solid plan now. I just wanted to run them by you to see if I'm going off in the wrong direction rather than keep reading the MOUNTAINS of overwhelming info:

Like you, I'm going to float my floor. Although I'm not sure if I "Need" to. But let's say I'm going to...

1. I've Dry-Loked all basement walls.

2. Now, I float the floor making sure that it does not come in contact with the concrete basement walls. I think I'm going to "wrap" the floated floor edges with Styrofoam.

3. Next, I'll build my walls ON TOP of the floated floor (FF).
(Important)The two sides of the control room that are up against concrete walls will be about 3 inches away from the concrete walls. They will be 2 layers of 5/8 rock on metal studs with 3-4" mineral wool.

4. The other (adjacent) walls will be up against the other walls of the live room - thus making a double-wall. Where ever there is a double wall, one side will be double layer of 5/8 rock and the other side will be double-layer of 1/2 rock.

5. Floated floors of the control and live rooms will be SEPARATE floors.

6. (Important!!) Ceilings: Which method do I do?

A. Do I install RC on the joists and then hang double 5/8 rock - and
then caulk around where the ceiling rock mates with the walls
rock?

B. Or can I actually "frame-out" a ceiling "wall" and then rock that?
Wouldn't that really make the room isolated? One issue is a loss of
height. With the FF and then a framed out ceiling - that means
precious ceiling height lost.


7. Glass will be one layer of 1/2 thick glass and the other will be 3/8 thick. These panes will be mounted on each wall of the double wall that divides the control-room and the live room. The air space between these "two" walls will be 9" (18" total thickness for all double walls).

8. All metal track will get acoustic caulking.

9. Any advice on spackling?

10. Do I make my walls 16" or 24" on center? Does this depend on the thickness of the mineral wool?


So how is this for a plan?

[AVare]

The clarifications did that great.

Yes, the construction method you describe that you want to use is correct.

Andre

[Aaronw]

If I'm reading this correctly, you don't need the gypsum on the side of the wall that is facing the concrete block. Will there be space between your block and your new wall? Or do you plan to build the framing up against the block?

[BradJacob]

If I'm reading this correctly, you don't need the gypsum on the side of the wall that is facing the concrete block. Will there be space between your block and your new wall? Or do you plan to build the framing up against the block?

Aaron,

There will be about 3 inches of space between the concrete and walls. Actually, there will be A LOT more on some of the walls because of SPLAYING them in the control room.

Could you comment on the ceiling questions? What of the two methods did YOU use - and what has been your experience?

Thanks Aaron...

- Brad

[Bassist_]

If I'm reading this correctly, you don't need the gypsum on the side of the wall that is facing the concrete block. Will there be space between your block and your new wall? Or do you plan to build the framing up against the block?

Aaron,

There will be about 3 inches of space between the concrete and walls. Actually, there will be A LOT more on some of the walls because of SPLAYING them in the control room.

Could you comment on the ceiling questions? What of the two methods did YOU use - and what has been your experience?

Thanks Aaron...

- Brad

I guess the only concern I have with this is that the sound escaping through the structure that is the "inner wall" of the control room will now bounce around in the space....

For completeness sake I would assume that there is not path out from around the structure and the concrete basement walls that hold up your house.... One possible path is upward toward the ceiling (your upstairs floor) and/or around the structure (the walls facing the concrete).

I've spent many years in isolated booths and have seen them installed and torn down. These pathways must be considered...

But I'm sure they are and I'm stating the obvious in which case... nevermind

)

Steve

[BradJacob]

Here's a drawing of what I plan to do. You can see the control room has two aisw that will face the concrete walls. The long top wall (26 foot) and the right side of the drawing are the walls that face the concrete. The left walls as weel - but this will be in the live room.

There will be points where the airspace is bigger than 3 inches - but it will never be any closer than 3 inches.

Now again, does anybody have any coments or suggestions on my original two methods of ceiling construction that I asked Aaron?

Any help in this area would be greatly appreciated!!!

[AVare]

Now again, does anybody have any coments or suggestions on my original two methods of ceiling construction that I asked Aaron?

The second is best acoustically. If you don't want give up the ceiling height then similar to what you wrote with the RC but RC is not good for LF isolation. Use RSIC or ISOMAX clips. The height loss compared to RC is 7/8". If that is tight still, use the RSIC-1 ext04 model. This can be installed to the same height loss as RC. Here is an URL on that model of clip.

http://www.pac-intl.com/rsic1_ext04.html

Of course still follow the practices of mudding and taping both layers, alternating the layer boards and acoustic caulking around the perimeter.

[knightfly]

"RC is not good for LF isolation" -

Andre, I've seen you state this a few times lately - this was my "gut feel" as well, but I haven't seen corroborating information - granted, I've not had time to sort through the 300+ walls in IRC 761 as much as I'd like - did you sift through that doc and note TL's for comparable walls with and without RC, or do you have another source?

Thanks... Steve

[Aaronw]

I have the latest pix on my ceiling construction. I just posted them this morning. Take a look...

http://johnlsayers.com/phpBB2/viewtopic ... &start=255

Aaron

[AVare]

"RC is not good for LF isolation" -

Andre, I've seen you state this a few times lately - this was my "gut feel" as well, but I haven't seen corroborating information - granted, I've not had time to sort through the 300+ walls in IRC 761 as much as I'd like - did you sift through that doc and note TL's for comparable walls with and without RC, or do you have another source?

That is exactly what I did several months ago for slightly different reasons.

The results for two wall systems, with and without RC are in this thread:

http://www.johnlsayers.com/phpBB2/viewt ... +isolation

I think I might go through IR-761 again and try and get all the relevant comparisions that are possible and post the results. Again, I will work with TL 125 Hz and lower and include STCs. This may take a day or two though.

Andre

[knightfly]

Andre, you're a real peach - any time you don't feel appreciated, it's just 'cause you're not paying attention...