Help needed on sub-floor prep

[WT21]

I need to attached a sub-floor, and I could use some advice.

I am remodeling a smallish master bath (11X7). The room is gutted to the sub floor. This mid-1970s colonial has 1X6 boards running diagonally to the joists, nailed into joists, as the sub floor. These boards (and even the joists) are kind of brittle, but we decided not to pull those boards because of the way walls sit on those boards, and the amount of work this would have triggered (this is a tight budget).


The plan: over the 1X6s will go 1/2" underlayment ply, and on top of that will got 1/4" birch ply with a vinyl flooring on top of that. The flooring sub will install the 1/4" and the vinyl. My job is to attach the 1/2"

The 1/2" underlayment is cut and ready to be put down. My question is how would you propose putting these down?

1. Screw the 1/2" directly to the joists with screws that will reach through the 1X6 boards (I think that would need to be 2 1/2" screws, as 2" might be too short?).
2. ring shank nail (maybe 1 5/8") to the boards
3. glue and ring shank to the boards (the 1X6s are not tremendously even, though, so the glue will have mixed effect)
4. glue and screw to the boards
5. glue to the boards but screw to the joists

My GC is suggesting #3, but I'm wondering why not screw into the joists and skip the glue (#1).

Also, although 1/2" ply keeps it floor-level to the rooms next door, I wonder why we didn't use 3/4", as that would have been stiffer. Do you think that would have mattered? Or maybe 3/4" play would have been too stiff, and 1/2" will conform to this floor better??

So, which attachment method do you think is best, and any comment on 1/2 vs. 3/4" ply?

Thanks for any help! I am supposed to attached this later today or maybe tomorrow

 

[WT21]

Any opinions out there? There must be some

Or is this the wrong forum for sub-flooring talk (as opposed to finished flooring talk)?

 

[Floorist]

The 1/2 should be OK. The underlayment should not be nailed to the joists and should not be glued. The rest sounds fine.

 

[WT21]

Why not nail to the joists?

>never mind. I just googled the idea of nailing underlayment to joists. The idea is the subfloor is (supposedly) firmly attached to the joists, and (again supposedly) permanent, and then the underlayment is only attached (non permanently) to the subfloor. Nailing only to the subfloor (and not the joists) allows for movement of the wood.

Too late, though, as I had already nailed into the joists. Luckily the flooring is sheet vinyl, so I think I'll be OK from any movement issues.

 

[Nick]

nail the underlayment every 1" on the edges , and every 6" in the field .

 

[DennisT]

I would run screws. Even if it is already nailed, I would add screws into the joists. Nails will eventually move and squeak. Screws don't.

 

[johnmet]

Proceed with the flooring installation. Once your subfloor is clean, dry, level, and structurally stable, you can install the hardwood floors. Make sure to install a moisture barrier underneath the flooring if specified by the manufacturer.

 

[woodfloorplanet]

glue to the boards but screw to the joists

The glue secures that connection and the screw locks it in place.