Sound Rated Walls

Architect

I have a wall in a school between two offices. Single stud wall to the underside of the concrete slab with sound batt insulation and 5/8" type 'X' gypsum wall board each side. I am calling for the gyp. bd. to go to the underside of deck on both sides to maximize the reduction of sound through the wall (over the ceiling). Another architect is telling me we only need to run the wall board to the deck on one side and stop the other side 6" above the ceiling. This is not a fire rated wall. Will stopping the wall board on one side still prevent sound transmission while reducing costs? Assume reducing sound transmission is more important than money, is it beneficial to run the wall board to the deck on each side?

Boycer88

run it all the way up esp in school, and the demising wall doesnt need to be fire rated?

and how much money will it cost to run the rock up another 2' ?

stuperintendent

Depends on the design of the ceiling as well is it a drywall ceiling? acoustic ceiling? is the ceiling insulated? are you using soundboard or resilient channel to acheive wall soundproofing? a good place to start is to find out what the sound transmission rating of the wall is, and design accordingly. the contractor will appreciate the savings if its not required to run the drywall up to the deck to get sound rating.

bh54

before you make up your mind look in a product called quit rock fro mthe us its is very expense but if you are not talk large areas it is what up are looking for

Chris Johnson

Why is a licensed architect asking us contractors this question? We build what you design and you get upset with us contractors if we question your working drawings!

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Chris

Architect

Thanks for the responses. I think running the wall board up on both sides will minimize the amount of sound traveling room to room. It should bounce the sound back rather than trying to absorb it in the sound-batt. The lay-in ceiling should reduce sound reverberation inside the room itself.

Chris: I, unlike many/most architects, value the best construction methods and don't have an ego so big that I can't take constructive criticism (no-pun intended - unless it's funny...) from someone on-site every day. I think the best thing an architect can do is go to sites regularly and talk to the guys laying the brick, installing the drywall, etc... and not just the contractor. Too many architects don't actually know how buildings go together; and that is a very sad fact.

BTW, I'm also a licensed contractor.

DavidNTX

Why not ask for an alernate to deduct 2' of gyp from 1 side of that type of wall. Then you will be able to compare cost savings vs the gained noise reduction. This might also be helpful if the job winds up over budget or if you want to involve the customer in this decision.

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Ted White

You will want that wall to be heavy and sealed. So drywall each side completely and seal up penetrations.

drywallr41

I think that should be a prereq. of all Archit.who are in school and part of their curriculum every year.I cannot tell you how many I have met that don't what actually goes on in the field.

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Sound Guy

Hi,
Your wall with board on both sides will be approx. STC 40 and it will be only approx. STC 22 with the single layer of board. The main problem is that drywall is stiff and rings at certain frequencies and it will pass through most low end voices etc. If there is any level of expected privacy they will likely not be happy with the single layer.

Ted White

Not exactly that large a spread in the STC curves. You have to compare data from the same lab to get a good picture. This data from the NRC in Canada:

Standard wall:

16" OC wood studs
Single 1/2" rock on both sides
light R13 insulation

STC 33-34

Add another layer of 1/2" drywall to each side and you get STC 38

Mass Law does not accomodate an 18 point gain as you described. A doubling of mass will give you only 6 points.

Sound Guy

Hi Ted,

You are right. Here is the raw data for a 1/2" drywall panel on its own.
Table 1: STC standard gypsum board panel ½ inch thick

Freq 125 250 500 1000 2000 4000 STC
Gypsum board 15 20 25 29 32 27 28


Bill Wilkinson

Darren@Partners

So what is the best way to stop the bass? Had a client inquiry last week about the same sort of thing.

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www.partnersconstruction-drywall.com

Ted White

First decouple the framing. Can be done with staggered studs, double stud walls or resilient clips. I would avoid resilient channel.

Next introduce a small amount of insulation. R13 is fine.

Add mass. Standard drywall is great for this. Double 5/8"

Add damping. Some damping materials work better than others.

Those are the 4 elements that you have available to you.