I'm installing hardwood over plywood over 6mm poly over asphalt felt over concrete.

I want to use insulayment as an underlayment: http://www.mpglobalproducts.com/images/ ... sheets.pdf.

Is it better to put this just under the plywood, or just under the hardwood?

Thanks

Great product Loose lay it on top of the plywood.

What is the logic behind laying the Insulayment on top of the plywood nailing base? Would it not help insulate the plywood substrate if it were installed under the plywood? In my way of thinking, the OP sounds as if he wants to install a plywood nailing base over concrete. Since many of us prefer the floating plywood substrate, wouldn't a better way be to:

1) lay out the 6 mil poly
2) loose lay the insulayment
3) float the plywood
4) lay out 15 lb. asphalt felt
5) nail down wood floor

Of course, one could simply eliminate the insulayment if one wanted to. It is not required for this system to work well. Out side of some potential noise reduction and helping thermal loss, I do not see much value in it for this type of installation.

Well for what ever it's worth.... When Global introduced Insulayment & Quietwalk they came out and had a presentation, sandwiches, soda, you know the gig.
They stated that the "Insulayment qualities of sound absorption & insulating properties are more effective directly under foot". Meaning not under an additional underlayment.

I agree that floating the plywood is superior. Granted, installing the Insulayment under the ply should add insulation & sound proofing. But IMHO installing insulayment over the top of the ply is the hot tip.

Basically, you are then saying it is more effective to lay the Insulayment directly under the flooring ( regardless of whether it is nailed down or floated ) and on top of the nailing base. Not trying to bust your chops but my concern in that method for a nailed down floor is:
1) losing the adhesive qualities of asphalt felt
2) a "squishier" feel
3) not recommended by any flooring manufacturer I am aware of. IE: putting "Volara" foam under a nailed down floor.

Now, for a floater, I can understand the logic. For a nailed down floor, I fail to see it.

Insulayment is designed for a gluedown or naildown install. Quietwalk is designed for floating.

You would be amaized at the difference between Insulayment & 15 lb. felt,( if the installer likes their 15pound felt, then roll it out under the Insulayment . It's a comfortable, solid feel , not to mention the difference in sound absorption & insulation ( it's not a foam product, & not "squishy", or hollow ). I cant tell you how much of this stuff I've rolled out, and the difference in the floor impresses knowledgable people.

Geez, I sound like their salesman

As Howard says, it is not squishy. I used it instead of felt upstairs, for sound suppression actually, and the floor is hard. I tried it and stomped over it, noticed it was less noisy than just felt. One of the rooms is above a garage that is not insulated. This room used to be cold always in the winter. It is nice and warm like the rest of the house now. That was a nice bonus, thanks Howard!

Now what Gary says is interesting though. Because of this: I'm going with 3/4" plywood nailing base, and this means 1.5" nails. With the 3/16" insulayment inbetween, the nail will sink that much less into the plywood. Just around 3/8" into the plywood if I'm not mistaken. I remember when I goofed something upstairs in the first closet where I was using 1.5" nails, it was fairly easy to pull the cleats out (I switched to 2" after that). So I'm wondering if I'm better off putting the insulayment below the ply.

Ideally I'd like to use a 1.75" cleat, but I don't know if anybody even makes them?

The alternative would be to put another 1/4" plywood and make it enough for a 2" nail.

Thanks, Anand

1 3/4 cleats are readily available. Powernail, Primatech, and presumably most chinese suppliers all have them. I recommend that you avoid off-brand products. I have found that in a lot of cases, they are either too hard and subject to breaking under stress, or too soft and bend when going in to the floor.

Thanks (Dennis either you are an early riser or late sleeper!).

I read the Insulayment pdf closely and there is a section at the end (maybe they recently added it) that says for use with plywood floating subfloor over concrete, put it right on the concrete. So concrete -> insulayment -> plywood 'sandwich' --> 15lb felt --> hardwood.

This also makes sense because they claim the material has additives to prevent fungal/bacterial growth. (I think it's traditional use is on concrete for tile.)

For wood subfloor it would be as Howard stated, plywood subfloor --> insulayment --> hardwood.

Back to the nails, in my case as I'm looking at doing 3/4" only floating instead of the 2 x 1/2", without the insulayment inbetween, 1.5" nails would probably be OK: I get just a wee bit more than 1/2" into the plywood, and I conform to the NOFMA nailing schedule.

This is what I was trying to say.




Plastic sheeting, Insulayment, plywood, felt then floor. Any other way makes no sense.