soundproofing with a layer of cork under hardwood.

I am building a house for a customer who is planning to do his own hardwood flooring installation (above grade, installed on 3/4" plywood.) He recently informed my that he intends to install a layer of 1/4" cork, then a layer of 1/2" plywood, then his hardwood strip flooring (nail down).
I have two concerns about this: first, wouldn't the fasteners that you use, both to fasten the 1/2" plywood and then to staple down the hardwood, penetrate into the subfloor and negate the soundproofing qualities of the cork?
Second, what do you think of nailing hardwood flooring into 1/2" plywood? I am somewhat skeptical about the nail holding ability of just 1/2" plywood.
Anyone done this or know about this?
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use 3" nails and go through the whole mess.

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wrote:

I suspect the sound will travel very nicely through all the nails.
Would you consider using a floating floor - Pergo type?
Richard
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<RCW> wrote in message

How much noise are you talking about?

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RCW <> wrote in

Aren't modern adhesives up to this sort of job? I read, for example, that wood glue is stronger than wood itself. So it seems to me (not that I know much of anything...) that one could easily question using nails in the first place...?
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Yes, but not totally. Is that why he's doing it?

Assuming we talking about 3/4" oak, I don't like that at all. I'm picturing premature squeaking at least, which would be kind of ironic.
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MichaelB
www.michaelbulatovich.ca
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Michael Bulatovich wrote:

Yeah, would just glue work? I find Carpenters glue is very strong. We basically use screws until the glue sets and then they're unnecessary. Ken

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:I am building a house for a customer who is planning to do his own : hardwood flooring installation (above grade, installed on 3/4" : plywood.) He recently informed my that he intends to install a layer : of 1/4" cork, then a layer of 1/2" plywood, then his hardwood strip : flooring (nail down). : : I have two concerns about this: first, wouldn't the fasteners that you : use, both to fasten the 1/2" plywood and then to staple down the : hardwood, penetrate into the subfloor and negate the soundproofing : qualities of the cork? :
It will probably short any isolation ability the floor had to airborne sound traveling through the floor but will have no effect on the impact reduction the cork will provide on reducing footsteps from traveling through. If he is interested in reducing the sound transmission coefficient of the floor ceiling system there are much better ways to get more isolation at a broader range of frequencies than you are trying.
start here http://www.recording.org/forum-34.html
peace dawg
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Plain wood glue the cheapest water soluted pva poly vinyl acetat --- think about the surface it engage and, you will not have metal rods transmitting the sound.
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Right that nailing through cork will negate much of the benefit. There are engineered wood floors that can be floated on top of the cork. It is tricky to isolate nailed-down hardwood. This is one specialty product that can work by floating the nailers with minimal extra thickness.
http://www.soundseal.com/impacta/soundeater.shtml
Isolating footstep sounds on wood frame construction can be very difficult, and you will always be left with a low-frequency thump to some degree no matter what you do.
For best results he needs to also isolate the ceiling from structure and install sound absorptive material in the cavity. These steps also help for airborne sound such as speech or music. The cork or other material under the floor surface is primarily to control the tapping sound of feet on the hardwood. It does not do much for airborne sound.
If he is serious, he should get professional help from an acoustical consultant experienced in wood-frame condo design.

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"Noral Stewart"> wrote

There ya go. Install a suspended acoustical ceiling on the 1st floor and blow the cavity full of insulation.
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yeah, i suggested resilient channel and sound batts as a much cheaper way to go (he is trying to save money) and perfectly adequete for a residential situation. But he has been doing internet research and has been told by companies that sell various fancy soundproofing products that resilient channel or dropped ceilings aren't the most effective way to soundproof. Which is true if you were building a recording studio, but for a house?
Oh well, he is going to be putting in 2000 sq ft of wood, after laying down cork (now it's acoustical glue under 1/2" plywood) and 65 sheets of 1/2" plywood. He doesn't have a clue of how much work he is up against. I get to sit back and say "I told you so".
Someone suggested spraying an inch or so of foam (either icynene or two part urethane) onto the bottom of the subfloor. Comments?
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"marson"> wrote

How thick is the cork and how is it packaged? Sheets, rolls? Why cork as opposed to say styrofoam?
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That's one way to make sure you've plugged all the air gaps.
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marson wrote:

Hey Marson, May be OT or not, but how is the double walled house you asked about a while back going? I remember you were asking about how to seal VB to windows in DW construction and have many times wondered how that project went/is going?
Sounds like you get a lot of customers similar to what we deal with hehe.
Mark
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really it's been going pretty well. they've been excellent customers. it's frustrating sometimes to deal with the profusion of "expert advice" available on the net. never know who knows what they are talking about and who is selling snake oil.
i got it dried in just over a week ago. it's a dang tower--30' to the eave on the walkout side. shelled it up with the outer 2x4 wall, and now we are going back and doing the inner walls and parts. it'll take a semi truck full of cellulose to fill those walls.
I oversized the ro's by 1 5/8ths and am boxing them in with 1x pine. will seal the window to that and the vb to the 1x box.
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marson wrote:

Wow good for you. Glad to hear its going well. Would love to hear more as it progresses.
Mark
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1/4" cork is an effective soundproofing. Where the most sound transfer will take place is at the perimeters, where the wood meets the walls- that is transfer of sound into the walls and down from there. The fasteners will transfer a smaller percentage of sound. Even with fasteners, the cork would help quite a bit.
I don't understand why the 1/2" layer of plywood on top? Why not just glue down the cork, then nail the wood directly on top of it into the 3/4" subfloor?
Also, there is 1/2" inch cork, and more expensive and thinner sound proofing membranes available that have higher sound proofing qualities and are denser if needed.
For a correctly done job, he should glue down the cork, then go directly over it with a 'floating' wood floor such as wood laminate (pergo). Then there wouldn't be any transfer of sound with fasteners, and since the flooring doesn't touch the outside walls- no sound transfer.
Many condo's here require 1/2" of cork, which makes a great sound proofing material and is inexpensive, and the pergo type floor can be laid directly over it.
I'm guessing at all this though since my subflooing/soundproofing experience is all with ceramic/porcelain tiles and I don't use fasteners (not for the tile anyway :-) In tilework the floor needs to be extremely strong so....... in my case I would add the 1/2" plywood to the 3/4" plywood, glueing and screwing those two together, then glue down cork (when soundproofing is required), then thinset down tiles.
thetiler
marson wrote:

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