Basement Studio - Isolation on Walls

[veatch]

Steve and crew,

I have some questions concerning double walls and isolation.

An old design is below (i have an update, but i can't get it uploaded to my ISP... ). It's off in a number of ways, but it's close enough to get me through these questions:



The CR and Tracking Room will be on seperate floated floors. The Machine Room will be on a raised floor, but no neoprene (it's up just for water protection, not sound iso...). The inner walls on these rooms will be built on these floors (room in a room).

The Iso Booth, Utility Room, and Machine Room will have (i hope) a single wall seperating them from the CR and Tracking Room, not the double walls shown in the picture.

Q1 - I'm thinking (can't calculate it, maybe someone here can...) that a single 2x4 wood stud wall with double layer of drywall (1/2 and 5/8 ) and 2.5 PCF insulation, and *no* RC would be at least 40STC. Will that be enough to keep Machine Room and Furnace/Blower noise out of the CR? (i would think so, but i've never taken an SPL meter into an enclosed utility room... just looking for a sanity check here... )

Next, i'm trying to eliminate the need for double doors ($$$). So, for the Tracking Room main door (at bottom) and the CR door (bottom right), i would like to make those walls a single stud as described above, but with RC.

Q2 - Is this OK to do? If so, exactly how?

Let's use the CR as an example (since that's the only part of the diagram that really hasn't changed between the diagram above and the current design ) Does the right-hand wall of the Machine room come all the way up to the inner wall, leaving a 1/4" gap to calk with acoustic caulk; the CR right-hand outer wall stop with the inner wall, turned back in within 1/4" and again caulked?

Q3 - For these two walls that will get RC, i'm thinking the RC should go on the outer wall, correct? My logic being that i will definitely be hanging traps on the inner walls, and hanging too much on RC walls is (i believe) a no-no...


Hope the Qs make sense. Hopefully i is bright 'nough to 'splain thangs without current pictures.

[knightfly]

A-1 - standard stud wall with 5/8 rock both sides, STC42 - this dips down to a TL of 21-22 dB from 100 hZ on down, so it would depend on the frequency of any rumble your furnace has - a spectrum analysis would help there. If you don't have such a beast, here's a free gold mine -

http://www.moonaudio.com/softwar5.htm

Use the Spectrum analyzer module to see what your furnace is REALLY putting out, so you'll be able (or I will) to determine what type wall construction NOT to use to keep from exacerbating the problem -

"The Machine Room will be on a raised floor, but no neoprene (it's up just for water protection, not sound iso...)" - say what?? Does your basement regularly flood or smell damp? If so, you need to do a LOT more homework before building things there - check this out -

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

A2 - The basic rules of isolation are pretty well laid out in the "sticky", "complete section" - you want two leaves of mass separated by air/insulation - the more isolation between leaves, the better - the more air gap the better, the more mass the better; the preference for isolation as far as frame type, from worst to best - single studs, no RC - staggered studs/same plate and cap or single studs WITH RC - light gauge steel studs (not load-bearing, and finally completely separate stud frames with no hard contact between them.

A3 - if you're gonna hang stuff on your walls, you're right about where the RC should go - with RC, you are building a "sprung" system - any change to the weight will affect the spring rate, which will change the characteristics of that wall from what you thought it was to an unknown quantity. By making the side you're gonna hang stuff on solid, you at least minimise, if not eliminate, that problem.

"Does the right-hand wall of the Machine room come all the way up to the inner wall, leaving a 1/4" gap to calk with acoustic caulk; the CR right-hand outer wall stop with the inner wall, turned back in within 1/4" and again caulked?" - not sure if it's just sleep deprivation, but none of that made sense to me...

Keep in mind, too, that when you add traps to a wall construction you lessen the isolation of that wall somewhat, so you should over-design your walls by a few dB to compensate for that loss of isolation... Steve

[veatch]

... here's a free gold mine -

http://www.moonaudio.com/softwar5.htm

Use the Spectrum analyzer module to see what your furnace is REALLY putting out, so you'll be able (or I will) to determine what type wall construction NOT to use to keep from exacerbating the problem -

Very sweet. This will take a while to get a measurement (we're not in the house yet), but it helps greatly!

Does your basement regularly flood or smell damp? If so, you need to do a LOT more homework before building things there

No water problems. I wouldn't dare put this in a basement that wasn't dry. By "water damage", i am concerned about 3 things:

1 - Hot water heater bursts - that's 50 gallons of water on the floor. A 2" lift is plenty to save your stuff....

2 - Sump pump(s) fail... yes, we'll have a backup (water pressure, probably), but hey, stuff happens...

3 - Severe weather, and water backs up through the sewer (there are some ways to protect for this...)

I've seen each of these happen to friends of mine - one lost both kick drums on a vintage Ludwig kit (hot water heater...)

The doc referenced is a great doc, and i do have it. Tanx again.

Bottom line, in Michigan, there are two types of basements: Those that have had water, and those that will....

Keep in mind, too, that when you add traps to a wall construction you lessen the isolation of that wall somewhat, so you should over-design your walls by a few dB to compensate for that loss of isolation

Great point - i'll definitely over-design (to the extent that i can afford... )

Regarding the use of RC, i just wanted to make sure that mixing a room's isolation won't cause disasterous results. The more i'm thinking about it, the more comfortable i am with it.

Tanx much for all of the great info! I'm sure i'll be a real pest in the coming months....

[veatch]

Duh... I just saw the "Add Attachment" function for posts....


The current design. Note the lower walls for the CR and Tracking Room. Here is where i'm concerned. I will use RC on the outside leaf of these walls, so i don't *think* anything will be shorted out....

[Aaronw]

In reference to hot water heaters...put a pan under it and find a way to add a drain pipe to it. It's doable, but you may have to raise the water heater. I wish now, that I had when I just installed mine 6 months ago.

Aaron