Soundproofing Brand-new Condo

[rnatalli]

I've been reading many of the topics here and think I have possible solutions narrowed down to a few options.  Basically, I too suffer impact noise from above and some minor airborne noise through the side walls.  Talking to neighbors only helps intermittently at best and if a new neighbor moves in, it's back to square one.  I've decided the time has come to take real steps to ensure quiet as we don't won't to move into a house for our urban living.

For the ceiling, I feel the following are the best options:

1. RSIC clips which involves ripping down our ceiling in a new unit.
2. Green Glue additional drywall to the existing ceiling.
3. Attach studs or furring channels to existing ceiling perpendicular to the original studs and then attach drywall filling the space between the old ceiling and new ceiling with insulation.

For the walls, I feel the best option is to add two more layers of drywall with Green Glue in between.

My questions are, does my #3 make sense or am I making the impact noise situation even worst by doing this?  Does Green Glue really work as I hear conflicting information?  And is there a better way to soundproof my side walls.  Any help would be appreciated.  Thanks!

[rnatalli]

I forgot to mention that for #3, I'm considering adding sound clips to the new studs and double drywall with Green Glue to finish.

[Mark Daveis]

Hi,
Just adding drywall layers with green glue in between to your walls or roof wont work because sound travels by conduction and will still get into the mass you have added with not much reduction. The best way would be to have enough air gap and build a floating roof/walls - green glue will add an extra 6 to 10 stc or so to this. But still building a floating roof and walls are quite expensive and difficult to do properly so I would also consider moving as it may be cheaper. If the impact sound conducts into your walls and hence floor then only a full room within a room will help. I have built these for myself but it is technically difficult, expensive and takes time to do right to achieve good results. Whatever you decide make sure you have enough air space and float things for the least amount of conduction and green glue will certainly help if you have a proper soundproofing design.

[rnatalli]

Moving is not an option.  Why would I move to something I need to spend tens of thousands of dollars to fix up the way I want when my only issue is soundproofing?  I'd rather spend half the money on soundproofing what we have now since it's brand-new and we have no reason to move or update anything in the future.  But thanks for the suggestion as moving is certainly worth consideration.

Some more information.  I used a sound meter to find that the impact noise from above rates around 60-65 db.  I've also noticed that at 50-55db, I barely here a thump.  Certainly not enough to disturb me.  So all I really need is about a 10db reduction to be happy.  The airborne through the walls barely registers so that should be easy to kill, but the impact noise in the ceiling is the killer.

[Mark Daveis]

Hi,
I was thinking of moving to a detached house with surrounding land/garden so you wont get any impact noise and would only have to deal with airborne noise which is easier and not likely to cost much depending on your location. I am in the UK so don't know how most people live in the USA - I would imagine lots of people have flats with no land of their own.
For the roof I would go for some type of floating roof with at least 2 inches or more air space and if done properly can give you the 10 stc you need. Green glue will help add more stc to a good design so its worth it just by adding a layer or 2 of glue to get the extra. Be careful as Low Frequency sounds are more difficult to reduce and don't use a less than 2 inch air gap or the gap will act like a solid giving much less performance. Check that the roof noise is not conducting into the mass of your walls as well - see if the walls vibrate when there is noise.

[joel]

Hi rnatalli,
Attaching studs or furring channels directly to existing ceiling dry wall will not help.  In fact, it will make the problem of impact noise transfer worse.  Tear off the existing ceiling dry wall.  Add bonded cotton insulation up inside the cavity to absorb (1.15 NRC) and block sound (15-17STC) within the ceiling cavity.  Add a layer of 1/8" MLV directly to joists in a continuous layer.  Install SSP Clips and DWFC for new structurals'.  Then install two layers of 5/8" fire code dry wall with Green Glue between.  The soundproofing materials for this are $7-$9 per sq ft surface area.  Be sure to leave a 1/4" gap where ceiling meets walls and fill with acoustic caulk.  Everone who has done this procedure have been most satisfied.  The least you can expect is 60-80% reduction in current noise.

Oh, by the way, you will want to do the walls FIRST.  Right now it sounds like flanking sound is coming out the walls.  Add a layer of dry wall with Green Glue to the existing walls first.  Then do the retrofit decoupled ceiling as described above so that it fits down inside the Green Glue walls.

[rnatalli]

Well, it has been several months and things are starting move somewhat.  Since the walls and ceiling don't meet Massachusetts building code, the homebuilder is preparing to correct the situation.  They recently did a test on the unit to the left of ours which is current unsold.  They used RSIC-1 over the existing ceiling, new insulation, and new 5/8 drywall.  I told them it was a mistake to build over the existing ceiling, but they did it anyway.  Turns out that this structure does meet the STC=45 and IIC=45 so they're going with it regardless that it could be done better.  Here's the structure in our unit as it stands now:

Wood trusses 24" OC with wood strapping running perpendicular at 16" OC.  The strapping is nailed where the walls meets the ceiling so it explains how sound is getting through to walls.  The air cavity between my ceiling and the floor above is pretty deep at 24" and does have insulation already.  My plan is to remove the existing drywall and cut the strapping along the joists as close to the edges of the rooms as possible so in essence they aren't connected to the ceiling in the middle of the room.  I also plan to add an additional layer of 5/8 with GG to what they plan already.  The demolition and additional 5/8 with GG would be done at my own expense.  I plan to do the demolition no matter what, but not sure what it'll cost per square foot do put up another layer of 5/8 and how much more benefit I would experience.

Does it sound like I'm moving in the right direction?  Thanks!

[stm]

Hi,
I was wondering what sound meter you were using months ago and where you obtained it. I am interested in acquiring one due to a problem very similar to yours.

Thanks

[joel]

To meet codes a person would need to have a certified acoustic consultant/engineer do the IIC and STC tests.  The sound meters they use measure dB at each octave frequency - 125,250, 500, 1000, 2000, and 4000 HZ.  Those professional grade sound meters cost $2000-$3000 minimum.  And for the IIC field tests an additional hammer tapping machine is required to provide impact on floor above ceiling being metered.
For general purpose STC sound meter go to Radio Shack - but don't just buy the cheapest one.  They have one that is OK - their Catalog No. 33-2050 (Sound Level Meter) - and reasonably priced.