I am trying to understand which underlay provides the best sound proofing for an engineered click-lock floating floor in a second story condo. The subfloor is 50 year old concrete slab. Our condo docs do not specify any particular material but in consideration of my down stairs neighbor, I would like to use which ever is best. I have asked an assortment of hardwood sales people, and it is a toss-up, general they tell me which ever product they happen to have is best.

Does it make any sense to glue 1/4 cork and on top of that use a product like Sound Muffler? Does 1/2" cork provide twice as much sound proofing as 1/4" cork?

Thanks for your expert advice.

Yes and I am not sure about the latter, although it would seem logical. Not fond of the floor muffler myself.

High rise condominiums in Las Vegas require Whisper Mat HW.
I just completed an installation on the 24th floor. I'm impressed with the product.

www.protectowrap.com

Although it may SEEM logical that adding twice as much cork would double its effectiveness as a sound barrier, it doesn't work out that way in lab testing OR field application. You will gain improvement but it really isnt necessary. IIC ratings are based on specific construction methods including thickness of concrete slab, is there a dropped ceiling below what type of flooring is being installed, etc. Not just the underpad used.
Most Condos establish their own requirements once the building is turned over to the corporation, check with building management for a list of approved underlays for the buiulding. And follow their guidelines! If there is a complaint from your downstairs neighbour, you want to be sure that you used an approved underlay.

Hi Dennis, believe it or not, I'm on the Board and we have no such requirements in our docs. We are a very small complex and the docs were drafted in the 70's when everyone had carpet. My condo had very cheaply installed tile with numerous voids under it when I bought it, it sounds terrible in the downstairs unit. This being said, I would rather install the maximum sound proofing underlay as an alternative to what a typical condo association might think is a minimum requirement. So the focus here is not necessarily deflection, but floor to floor noise transference. I'm removing the old tile prior to installing the wood floors.

Would you say cork is a better choice in this situation or a foam or rubber type underlay? If cork, is 1/2" significantly better than 1/4"? For the latter, which specific manufacturer would you say does a better job? Thanks!

The cork products we use here can be found at: www.jelinek.com
This is a fine product, and made specifically for sound abatement.
There are other synthetic products out there, but in general are not manufactured from a completely renewable resource, nor are they any more cost-effective.
Some products you COULD look at are: Regupol, Acoustitech, and Durason.
These are all highly rated, i.e. greater than IIC 60, so are approved by most condo boards. You may; given your position, approve any of them for use in your building, lol.

As to doubling the thickness of the cork, in general, going from 6 m.m. to 12 m.m., will double your cost with at best a 10 percent increase in efficiency, if any.

It sounds like the key here is making it sound better than it did previously.....so, obviously, no matter which underlay you choose, your downstairs neighbor is going to benefit alot over the tile that was there before. That being said, Regupol is the one I tend to see more often than not for condo projects.

Thanks everyone for your good advice. I think I have enough info now to make a well informed decision. This site was a great help!