Sound Isolation in Condo - AIIC of 60 Needed - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 5 Old 03-30-2020, 10:31 PM - Thread Starter
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Sound Isolation in Condo - AIIC of 60 Needed

We have a condo project with a simple and straightforward challenge. First off - I've already recommended a great acoustician to the Client, as we always do in situations like this. So no need to advise me to hire an expert :-), one has already been recommended.

In the meantime I did a little research on it myself. The requirement for this building is an AIIC of 60 between floors. To achieve this, a 3" or so floor build-up is required per condo specs, and the Client does not want to lose 3" when the ceiling height is already around 8'. So we'd like to come up with a floor assembly that can hit 60 AIIC, uses real wood and doesn't eat up 3".

The floor is an 8" concrete slab which measures 32 IIC. Having looked at numerous underlayments, they all top out around 25 DB (using Delta IIC and not the bogus IIC ratings most of them provide). So 32 + 25 = 57. The Client has had a few different underlayments tested, and the highest IIC they've been able to achieve is 59, one short!

So the question is, are there any underlayments out there with a Delta IIC of 30 or so, that can be used with hardwood floors, and help us to get past 60? I've looked but have not been able to find one.

Thank you in advance for any assistance.
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post #2 of 5 Old 03-31-2020, 07:29 AM
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The most aggressive floor design I've come across is to lay down a layer of 3/8 to 3/4 rubber pad, Then float two layers of 1/2 subfloor material with Green Glue between layers. Floating means no mechanical fasteners through the rubber. You stagger the sheets and screw them to each other forming one monolithic piece of floating sub-floor so it will stay in place, then do your hard wood on it, with nails that don't penetrate the rubber. Unfortunately it takes some vertical space and there might not be published data if you have to submit for approval.

Personally I've done a single layer of 3/4 T&G on the rubber, in that case you have to add glue to hold the sheets in place. DA5 adhesive with a 3/16 V notch trowel.

Here is one source of rubber mat: https://www.soundproofingcompany.com...a-mat-underlay, You might reach out to see if they have any useful test data.

The poor mans solution is to get some horse stall mats from Tractor Supply. cheaper per sq ft.
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Last edited by BIGmouthinDC; 03-31-2020 at 08:26 AM.
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post #3 of 5 Old 04-01-2020, 07:40 AM - Thread Starter
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Thanks Jeff. Unfortunately that would only get us a little less than what is currently specified, a number I should have mentioned in my first post. The "accepted" condo buildup, assuming 3/4" T&G floor, is 2 5/8". Your solution would come to 2 1/8". A worthwhile difference I think, but not acceptable to the Client.
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post #4 of 5 Old 04-01-2020, 07:45 AM
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Non-expert here but is there anything you can do in under 3" that 8" of concrete couldn't do ?
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post #5 of 5 Old 04-01-2020, 08:11 AM - Thread Starter
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Quote:
Originally Posted by HFGuy View Post
Non-expert here but is there anything you can do in under 3" that 8" of concrete couldn't do ?
You have to look at it as a whole. For instance, if you add a 3/8" underlayment with a Delta IIC of 25 on concrete, you get around 57, but if you add a second layer of underlayment on top of that, it doesn't help and you don't end up with 72, you're still going to be near 57.

Yes, a 3" buildup can get you well into the 60's, because that height allows you to use an underlayment and a couple of layers of plywood on top of the concrete.
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