what is the best type of sound insulation?

Question

what is the best type of sound insulation to put under a wooden floor. I am doing an attic conversion and have a plywood base on the 2nd floor and wish to put sound insulation between the plywood and the final pine flooring. I have heard acquistic cork is good but trojan underfloor padding is cheaper.What brand names can people recomend?
How good are they ?

Answer 1

See the links for several options. Others can be found with a Google search (floor+soundproof). The degree of "soundproofing" will depend on thickness and material chosen. Note, however, that all of these materials will only work right if there are no nails or screws from the top layer (finish floor) into the subfloor to creat bridging (or coupling of the two surfaces). The sounddeadening works by decoupling the vibration (noise) of the finish floor from the subfloor and joists. This means you should be thinking of a carpet or floating laminate or glue-down hardwood mounted onto a second plywood subfloor layer ($$) above the sound deadening material.

Answer 2

As a general rule, heavy materials reduce sound much better than lightweight materials. The heavier and thicker the material, the better the insulation. One of the best sound insulation materials I have used is a rubber and lead foil composite - I've used it to silence generator sets.
I used Boardwalk Underlay under my floor, it's a rubber and foil material. It seems to work well. There is another called Technics 5 that is slightly thicker and has higher performance figures.
For a top notch job, you could insulate between the rafters with rockwool, then between the floorboards and finish floor with a sound reducing underlay.

Answer 3

With all due respect, part of the job should have included sound insualtion UNDER the flooring, but rubber/vinyl based underlayment is as good as cork, and CORK will be far more costly. Not only more costly but degrades at a much faster rate than the approved laminated vinyl/sponge underlayment products sold today.

Another issue is the securing of both the underlayment and the floor, in the event that there are voids on each rafter/beam.

At this point your better option is more research. The underlayment by the way is NOT strictly designed as a sound deadening substance, but a cushioning one.

Steven Wolf

Answer 4

Right, if you really want to deaden the sound the best way forward is that when you have laid the plywood you then lay rolls of felt. Felt incidently is what they used to put in cars to deaden sound. I strongly advise you to be very wary of all the "sound deadening material" that is on the market and speaks of decibels in this way and that.
When you have laid the felt fix your finish flooring as you have already suggested.
Make sure you have sorted out any pipework and electrics beforehand.

Answer 5

if you put any type of soundproofing in between the ply and the flooring then you are asking for a very squeaky floor ..you should have bought some rock wool sound proofing bats ..not fibreglass and laid them inbetween the joist ..filling every space to acheive some form of soundproofing these csoundproofing bats are very dense and quite heavy but if laid tightly without any gaps they will work very well

Answer 6

Mineral wool insulation

Answer 7

the best sound insulation is the same material corks are made from! you know wine corks!

Answer 8

stirofoam.... egg cartons... I agree with the carpenter it should have an underlayment