Subfloor – what size screws and where?
hurnik
| Posted in Construction Techniques on
I’ve got “plank” subfloor laid on the diagonal in a 1950 Cape Cod house. Before laying the extra layer of plywood on top (for a tiling project), I’d like to tighten down some of the “loose” planks (they were nailed in and no adhesive).
I assume I would use 2.5″ screws for the joists (where the plank is on top of the joist)?
When laying down the 5/8″ plywood on top, I’ll be using adhesive and screws.
The question is what size screws for THAT and where?
I’ve heard to NOT screw the extra layer into the joists, just the subfloor itself.
If that’s true, I’d use like what, 1 5/8″ screws? (plank is 3/4″ thick).
??
Replies
How thick are the planks? Are they relatively uniform thickness?
Are they flat, level? If 1", your screws are more than adaquate.
For the 5/8 plywood I would use 1 1/2 screws with the
cutting nibs on the head.
larry b
The planks are 3/4" thick (I had a small section I had to cut up to move an air duct and replaced that section with 3/4" Advantech OSB, and it's the same height).The boards are flat (not cupped at the ends), but I wouldn't say that they're 100% uniform (thickness yes, but there's a few small sections where they may have warped a smidgen between the joists).
Also, pull all the loose nails...especially any that are "shining" down below.
Are you going to tile ontop of the subfloor or use a backerboard or ditra over it?
TCA has specs for laying tile on plywood where you have 2 layers and t he top layer is only to be scewed to the bottom layer.
Likewise when using backer borad over plywood sub-floor the backerboard is only to be attached to the sub-floor.
They don't spec a plywood over board sub-floor.
So if you are putting somethig over this playwood (backer or ditra) then I think that you want to attach it to the joist. But that is mostly guessing.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
The thought was (according to Ditra manual) to put 1/2" Plywood over the 3/4" structural plank flooring, and then Ditra on top of that.I'll double-check the Ditra manual to see what it suggests for putting the 1/2" plywood over the existing subfloor.Yes, all sorts of interesting finds when you see the old house. Loose nails? Never (haha). Pull those suckers out and use new screws.Ideally I would have removed the entire subfloor and put new stuff down, but to be honest that would've entailed WAY more work than I have time for (a bit hard to shuffle all the appliances around and work around the cabinets).Thanks for all the help!