[Greenbuilding] second floor wood floor over insulation layer - questions

[John Salmen]

Any mechanical connection (screws, nails) transmits sound – also anything
rigid (sleepers, framing blocking, plumbing etc.) so you are best off
floating the next floor assembly and building on top of it (as is done
commercially). 

 

What you are trying to do is convert sound energy into heat basically. So
materials that absorb and reduce the transfer of sound by interfering with
it (reducing vibration). Layers of dissimilar material can work much better.
Initially I would look at something like a cork layer adhered to the hemlock
decking with acoustic sealant and then a layer of foam adhered with acoustic
sealant to the cork followed by a layer of drywall (cheap and the weight
holds down the foam and cork. I would then laminate ¾ sheathing to that with
acoustic sealant – I might even consider two layers of thinner particle
board sheathing with acoustic sealant between (changing the orientation of
the sheets between layers). The acoustic sealant (vapour barrier sealant) is
key as it doesn’t ever set or harden so allows each material to float
reducing transfer of energy by vibration. 

 

The assembly has to be thick enough to isolate nail penetration of the
flooring above which usually sticks through the sheathing by ¼ to ½ “. Floor
plates for walls should ideally be glued with minimal nailing or use a
gasket – don’t let wall drywall touch the floor (its not just the floor
think of the room as a giant speaker – compressing some insul batts along
the floor line in walls – anything that can absorb sound from the room
before it hits the floor). Edges of the floor sheathing should be isolated
from touching the exterior walls. Everything has to float like a boat. The
nails through the oak flooring into the sheathing will hold everything in
plane.

 

I would look at the weight of that assembly see if it worked with the floor
structure and the budget and then tinker with it. Dissimilar materials in
layers that both provide both high density for absorption and low density
for isolation.

 

 

From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org]
On Behalf Of Reuben Deumling
Sent: December-10-12 5:46 PM
To: Greenbuilding
Subject: [Greenbuilding] second floor wood floor over insulation layer -
questions

 

I'm going to be remodeling a two-storey house where 1/2 of the upstairs will
become a ~ 600 sq ft apartment. To that end I'm planning to add a layer of
something  to the floor (in between the existing decking and future finished
floor) for both sound and thermal insulation. All that is there now is 2x6
T&G Hemlock decking. I want to install an oak floor above the insulation but
have not done this before and am curious to hear your suggestions.

The only thing I've come up with so far is rigid foam with T&G plywood on
top screwed through the insulation? 

Thanks very much. 

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