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?
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
: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
: 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
: 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
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.
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.
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?
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
Sounds like you get a lot of customers similar to what we deal with hehe.
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.
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.
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