Solid Hardwood, Engineered and Laminate Flooring - subfloor repair/installation

I'm doing some subfloor repair work and need advice.

Currently, I have 5/8" plywood resting on joists and on top of that another layer of 5/8" (plywood in some areas, particleboard in others). In between both layers is black vapor barrier (I guess that's what it is). I pulled up some damaged particleboard and will replace it with plywood.

Do I need to patch any small nail holes or tears in the vapor barrier that resulted from pulling up the old board?

What size and type nails should I use for the new plywood?

On top of this, I am installing 1/4" luaun for vinyl underlayment.

What size and type nails should I use here, since I know the particleboard won't hold nails well? Should I try to go through the bottom layer of plywood with ring shanks? Should I also use liquid nails?

Thanks,
Brian

First: Rosin paper is so cheap, if you're concerned about vapor barrier, go over those spots with new. Fastening down new plywood, you want to go INTO joists. So if plywood is bottom layer, 1 1/4 ring shank nails, or coarse thread sheet rock screws will do fine. When you go to lay 1/4" luan, use some liquid nais construction adhesive. Because of particle board in some area, you may want to go up to a 2 1/4" screw or nail. Hope this helps. Good Luck.

Great -- thanks!

I haven't been able to find the barrier material, which you say is rosin paper -- I can find asphalt roofing stuff, though. I was thinking I might just patch the holes with caulk, even though ijust to be safe.

Also, it's hard to find ring shank nails in longer sizes. I found 1-3/8", but that's the longest. Do I need ring shank nails that specify 'for underlayment' or are drywall ring shanks okay?

Any home improvement store will have rosin paper. Roof paper will work too. Any ring shank nail will do the job. If the area you're doing is small, I'd opt for the 2 1/4" screws, using a screw gun. If the area is quite large, you may want to go for a rental of air compressor and framing nailer. I have to nail down 250 sq ft plywood. That's what I'm doing, using a air driven nailer, just because it's faster. Good Luck.:)

I'm doing about 550 sq ft -- one-half at a time. I may get the nail gun.

Nails = squeaks!!!!

Use screws!!

The second layer of plywood should run the opposite direction of the first layer of plywood.(This never gets done in the real world. Mostly from lack of education on the subject of expansion and dimensional stability) This adds deminsional stability. Nailing into the joist, only for the first layer. The second, layer is to be only nailed to the first layer.

Besure to leave expansion gaps around the perimeter, and don't but the panels tightly.


Acclimate the plywood for 2 days prior to installation, just the same as the finished wood flooring.

Just curious, why nail first plywood to joist and then nail second plywood to first plywood?
Why not screw?
Why not screw (or nail) top plywood through and into joist also?
Thanks
Scott

Only because I saw Perry Wright post a similar response on another board:

I believe the idea is that nailing all the way through the bottom layer of plywood lowers the nail's adhesion to the plywood and lessens dimensional stability of the entire structure. Fastening the top layer to another layer that's fastened to the frame would be more structurally sound than trying to fasten both layers to the frame, but I'm not sure the margin of difference. In a Mechanical Engineering analysis, there would be quite a bit of statics involved. I'd be interested in more detail, though.

I think screws are a different matter because of their much stronger holding power, but it's more expensive and much more time-consuming to use screws over nails using an air nailer.

Wood expands and contracts. Its dimensions dictate which side is going to expand/move more. ( 4x8 ) the 8' direction is going to move expand and contract more then the 4' side of a single sheet. Now if plywood were 4x4, we wouldn't have as much of a problem, but then wood grain comes into play. 3 ply, or 5 ply you have more grain layers going one direction then the other.


When I said nails off in the last reply, I meant fasten off.

Use the fastener of your choice, ring shank nail or screw.

I'm still confused about fastening the top layer of plywwod to the bottom or through and to the joists?

To Scooter: I'm also doing a subfloor. The idea is to get the greatest holding power and stability of the whole floor. By laying top layer of ply across the lower layer, then SCREWING it all together into the joist, you're assured of a solid foundation. I also plan on using liquid nails underneath plywood. I have too many squeaks already and I'm trying ti eliminate them without creating a new ones. Hope this clears it up for u.