I’d like suggestions on sound-proofing an existing library wall. We’re going to remodel an office with library shelves on the wall to be sound-proofed, so we have the opportunity to add sound-proofing between the existing wall and the back of the new library cabinets.
Gary W
A 1225-sq.-ft. detached ADU uses a sloping lot to its advantage, featuring a split-level entrance and vaulted ceilings.
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Replies
What kind of sound are you sound proofing against?
As this is an office is this walls within a larger building? IE, is there suspended ceiling about the office and the the other side that can leak sound?
What are these libary shelves?
Floor standing shelving like in a Library Libary? Tracks mounted on the walls with adjustable shelves? Full cabinets?
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
The office is next to a guest bedroom in a single family dwelling. We're asked to sound-proof for talking and low volume TV or radio. The library shelves are cabinets with backs and they'll be attached to an existing, 2x4, 5/8-inch sheetrocked wall separating the office from the bedroom.
Thanks for your offer to help; I look forward to replys.Gary W
gwwoodworking.com
I would think that dense packing the walls with blown in cels would probably do the job.If not then install resilant chanel over the wall and a layer of sheetrock on top of that..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Use mineral wool batt insulation between the existing studs. Strap the studs with resilient channels and use RSIC-1 sound isolation clips. Caulk all drywall joints and openings before taping.
That will handle the noise that comes through the wall, but there may be flanking paths through the floor and ceiling that negate the gains you have made.
fingersandtoes,
Those flanking paths are virtually a certainty in an existing house where no sound control measures were planned in from the beginning.
If so then the possible gains are not great, no matter how much effort you spend on the wall surface. I'd recommend not spending too much effort on it. Add another layer of 5/8" drywall to one side, tape, sand and paint. Caulk underneath the new drywall. Install shelves.
Ron
What Ron Budgell said, but I would add a layer of Green Glue between the two layers of drywall. It acts to damp the whole assembly over the complete range of human hearing. It makes a huge difference when it dries. Before it dries, it sounds no better than the added drywall without it. It can take a week or 3 to dry, but when it does, the difference is amazing. Green Glue adds about a dollar per square foot to your materials cost, and makes a huge difference. Their website is also full of good information.Definitely do NOT add RC over the wall, and then another layer of rock. It will do almost nothing for you, and be a huge hassle. Adding just the drywall is not only easier, but also more effective than RC in this application.Bill
You are both probably right about the flanking path, but don't you think it is a good idea to get into the wall and insulate? Extra layers of drywall on a hollow wall aren't going to do much.
In terms of measured STC ratings, resilient channel with sound absorption clips gives you a much larger increase than any combination of mass added products, glues or layering of drywall in the wall assemblies I have seen measured.
Actually, extra layers of DW on a hollow wall do quite a bit. It is the fluff in the cavities that does very little to attenuate sound, only helping in the highest frequencies where an adequately air-sealed partition already does okay.The reason is that the sound excites the assembly itself, bypassing the stud cavities.Resilient channel works well on a raw wall, that is, mounted to the studs with drywall over, provided none of the screws bridge between the RC and the studs/plates. Sound clips are better than RC.To understand why DW-RC-DW is not very helpful, do a Google search on "triple leaf effect".Ordinary glues do nothing for acoustic performance. Green Glue and its direct competitors are viscoelastic compounds that do a lot.Persnickety air-sealing does the most for the least money for reducing high frequency transmission. All gaps have to be sealed, even tiny cracks and pinholes.Bill
To be honest, I haven't done any soundproofing to existing walls. All my experience has been in designing party walls between residential units using tested wall assemblies.
I do know that adding sound attenuation components on an individual basis often has unpredictable consequences. Sometimes even diminishing the wall's rating. By removing the drywall on one side and then using the method I suggested, you end up with a wall assembly which has a rating of 50+.
I have looked at a lot of wall assemblies, and never seen one without insulation. In fact most of the assemblies make the distinction between different types of insulation used - and it affects the STC significantly.
My feeling is that if a client has asked you to do something about the sound between two rooms, he is not going to be content with seeing you do work on it and not get significant diminution of the sound passing through it. The only way that I could guarantee that is to reproduce a tested assembly. You, having more experience with this in real world conditions, might do very well with your suggested solution.
I wanted to clarify that the isulation in the cavities is not without merit. In remodel situations it can be very expesive to do a destructive upgrade, and even blown cellulose is somewhat destructive to do on an existing wall.In new work, cavity fill is a given, the denser the better. On remodel work, dollar for dollar, the surface-applied solution makes far more sense if it alone can give the needed results.The STC ratings are also problematic, since the standard fails to account for some very significant bass tones, which are the easiest to hear through an assembly.Like you mentioned, stripping one wall face will allow you to create a rated assembly of known perfomance, ignoring flanking paths for the time being. That will perform a lot better than the DW-RC-DW sandwich discussed earlier.Personally, I dislike resilient channel, having done a few jobs with it. It introduces a host of new headaches, is not very flaw-tolerant, and is a pain to do right. I much prefer the double wall, or a stagger stud wall. If a client hangs bookshelves later on an RC wall, the RC is bridged, the screws in the DW can pop, and the shelves may fall off the wall. It is a minefield in the real world.Anyhow, if you reproduce a rated assembly, you should be okay, and have legal coverage, too. I mostly wanted to warn you off the triple leaf that some were suggesting be done.Bill
"The STC ratings are also problematic, since the standard fails to account for some very significant bass tones, which are the easiest to hear through an assembly."
Thank God for Ipods. The most significant change in sound attenuation since the 70's is probably the disappearance of fridge sized speakers in every teenagers room.
We just finished a project and used Green Glue between 2 layers of 5/8's and can foam to provide some sound insulation between a bedroom and a living room. To my ear, it worked way better the the RC/DW/sound insulation/homosote methods I've used in the past.
I know, it is amazing stuff. How long did it take on your job until the damping effect really kicked in? When I did the subfloor in my own bedroom it took 9 days until the damping was noticable. When that happened, it blew my mind. Suddenly walking on the upper layer of plywood was like walking on a beaten earth floor, as far as the sound it made.Bill
if the wall is 5/8" drywall already... use 1/2" IF IT'S 1/2" USE 5/8" any sound that will pass one will pass another like it... that why the change...
any one part polyurathane liquid nails type product pl200 i think is common... glue and screw it... glue on a 1ft x 1ft grid.... screw it up... let it set then remove the screws (use as few screws as you can...) caulk all the edges... have no outlets in the wall... put up the book cases attach them to the floor and ceiling only if you can... fill with as many books as you can... full is best... books have huge mass
prob the best you can hope ......
p
What I would do is add RC-1 channel over existing rock, then another layer of rock leaving 1/4"gap all around and sound caulk it. Also would consider pumping cellulose in the wall first. Maybe even use Quietrock.
Lots of information out there.
Mike
Trust in God, but row away from the rocks.
Add a layer of QuietRock - that is your best option. It will out-perform all other options.
It IS $300/sheet however
Jeff
I am thinking about using quiet rock and insulating my wall with safe N sound roxul insulation to abate traffic noise.
http://www.quietsolution.com/html/quietrock.html
# A single layer of QuietRock 525 is equivalent to 8 layers of standard drywall (acoustically).
# 10x more reliable than resilient channel with no resilient channel liability risks.
# Use like standard drywall
http://www.roxul.com/sw47802.asp
Roxul Safe ’n’ Sound™ insulation is 25% denser than thermal, exterior wall insulation and the higher density makes it very effective as a barrier to sound. In addition to the density factor, the non-directional fibre structure of each batt creates thousands of tiny, inter-connected voids. These voids trap vibrations created by sound waves that penetrate the wall. Once these vibrations are trapped the sound energy dissipates, significantly reducing the transference of noise from one room to another.
http://www.cmhc-schl.gc.ca/publications/en/rh-pr/tech/02-108.html
SamT
CMHC publishes tons of great research. You can even call them up and usually you can talk directly to one of their dorky scientists.
Hi Sam, and everyone else who replied to my question.
Work has tied me up and prevented me from writing a timely reply, and I've also been digesting everything posted here. There's less work out there right now, and I'm scrambling to find the next project and write proposals.
I've also been talking with my sub-contractor about what I'm learning. We're leaning toward the simplicity of foaming the existing stud bays and sandwiching green glue between the the existing 5/8 rock and another, new layer of 5/8 rock. My client has lived with the lack of sound proofing for years, and just wants to take advantage now and add some. One thing I find interesting is that sound proofing improves after a few days allowing the glue to set.
I'll let you know what we decide to use and how it works. Gary W
gwwoodworking.com
SamT