Hardwood Underlay

[1990C4S]

I am installing 4" wide x 3/4" thick prefinished maple tongue and groove hardwood onto a plywood subfloor. I have zero humidity or moisture issues.

I wanted to use Aquabar B as my underlay, but it is not available in my area right now.

Other options are waxed paper, which I have used before with zero issues:

https://www.homedepot.ca/product/roberts-750-sq-ft-3-ft-x-250-ft-x-009-inch-waxed-paper-underlayment-for-wood-flooring/1000496301

Or I go with 15 lb roofing felt.

Any reason not to go with the paper? Should I wait two weeks to get Aquabar? I don't think I really need it.

[gregpark]

Wax paper or visqueen will block vapor just fine but 15lb. felt is what I would use in liu of Aquabar though. No chance of a noisy floor.

[Bugsinrugs]

I’ve used Kraft paper in a pinch.

[1990C4S]

I think I have a roll of roofing felt in the shed...I was also wondering about Tyvek.

[OK-944]

You need something with a bit of "springiness," otherwise it will be very noisy (so no kraft paper or tyvek). Don't go with roofing felt as it will smell like tar.

You should look into a foam product from HD - I used the thin pink foam (cannot remember what its called) with self-adhesive strips along one edge...to lay engineered maple in my converted basement rooms.

[1990C4S]

I have never added anything 'springy' under a nailed hardwood floor. Only paper.

[908/930]

Is the subfloor over non heated area? Over conditioned space I would do at least partial glue down, there is proper floor glue for this.

[1990C4S]

The floor is over a heated/cooled office in the house.

Instructions say nails every 9-10". That is how I did the last five floors.

[dad911]

15# felt, or rosin paper.

[gregpark]

Since this is a nail down use the felt. Any springy foam pad can lead to fastener noise eventually. And I don't use nails, I have cleat nailers using ribbed cleats. You can rent one and it's worth it on installation time saved alone. We use cleats because they will never squeak. A cleat every 9" minimum, 2" from all butt joints

[1990C4S]

Originally Posted by OK-944

Don't go with roofing felt as it will smell like tar.

I wondered about that too. Doesn't roofing felt smell like tar? Or does it dissipate quickly?

[gregpark]

15 lb. felt will emit no odor. I've used it hundreds of times over the last 50 years as a vapor barrier. I only prefer Aquabar because it's lighter to handle and cheap. No need to overlap it either as you're just blocking vapor.

[Evans, Marv]

When I had my floor laid down, I used Tyvek and an underlayment. Mine is 3/4 in. X 1.5 in. quarter sawn oak done eleven years ago now. Maybe I was in error at the time using Tyvek, but I haven't had any problems with moisture, noise, or anything else since installation.

[gregpark]

Tyvek is a moisture barrier and would work just fine under hardwood. So would wax paper. Rosin paper would be pointless though. You probably wouldn't have a noise issue with any of the suggestions. I do this for a living and don't take any chances that's all. You need nothing at all if you live in the desert and have no moisture under your house.

[mepstein]

Tyvek is a water and air barrier but not a vapor barrier. Like Gore tex, it's designed to let vapor pass through.

[gregpark]

Did not know that!
Forget Tyvek as a floor membrane then

[Evans, Marv]

Oh, great!

[gregpark]

^after 11 trouble free years I think you're fine

[1990C4S]

Originally Posted by gregpark

Tyvek is a moisture barrier and would work just fine under hardwood. So would wax paper. Rosin paper would be pointless though. You probably wouldn't have a noise issue with any of the suggestions. I do this for a living and don't take any chances that's all. You need nothing at all if you live in the desert and have no moisture under your house.

That was my thinking, thank you for the info.

[stealthn]

You don’t want to use something that can retain moisture. We used a product from Schluter Systems, I forget what it’s called but they have a bunch of good stuff.