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Subfloor creativity

jonny_h | Posted in Green Products and Materials on

Zone 5, though it doesn’t matter for this discussion. 

Substantial ongoing remodel project, where we’ve gutted the entire second floor of the house, down to removing the existing subfloor (1/2″ water-damaged plywood) to do some structural work.  In a bathroom and laundry room, we’ve already installed new 3/4″ tongue and groove plywood subfloor, glued and nailed, which will be tiled over (probably using a Ditra system). 

Bedrooms have yet to receive new subfloor, and plywood is increasingly expensive.  Desired finished floor is wood.  Doing the work ourselves, so contractor cooperation is not an issue.  So, a couple creative ideas:

1: Use old-school 1×6 or 1×8 pine board subflooring, installed diagonally — Looks cost competitive with plywood, possibly more available, and avoids any formaldehyde based glues (though I understand offgassing with CDX is a minimal to nonexistent risk).  The first floor of this house is done like this also.

2: Just use thicker (like 5/4) tongue&groove hardwood flooring directly on the joists.  Seems like it’d be just as robust as thinner stuff over subfloor, and would be installed in a single step, though adds a bit of complexity in terms of how interior walls would be framed.  Any major disadvantages to this kind of approach?

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  1. walta100 | | #1

    Every squeaky wood floor I walked on has had a 1x subfloor under it and the silent ones all had OSB or plywood coincidence?

    What a crazy world $2.75 a SQF for subfloor.


    1. Expert Member
      NICK KEENAN | | #6

      T1-11 is $100 a sheet. It's luxury siding now.

  2. Expert Member
    Michael Maines | | #2

    I'm currently working on two projects using lumber and sheathing boards cut on site. They are as low-carbon as we can reasonably get. But on both projects I spec'd Advantech for the subfloor--I've worked on a lot of old houses and they always have squeaky floors.

  3. Expert Member
    BILL WICHERS | | #3

    I see no problem using old-school plank subflooring. I wouldn't try to make the finished floor also the structural floor though, and that might get you in trouble at inspection time too.

    Regarding squeaky floors, I've had plenty of squeaks in plywood, even the T+G plywood used in my own home. Run a bead of glue on top of the joists prior to installing the subfloor, and use screws or scrails (or at least ring shank nails) to put the subfloor together. Squeaks happen when the subfloor can slide along a loose nail somewhere. Glue and fasteners that can't slide solve this problem.

    Note that I've often found squeaks are coming from bottom plates of nearby walls and not the floor itself. I've solved this when needed by removing the baseboard, then running a few big screws diagonally to tie the bottom plate into the subfloor or whatever else is under it. Once everything is locked together with screws and can no longer move, the squeaks stop.


  4. plumb_bob | | #4

    BC Building Code allows for wood strip flooring to be laid without a subfloor if it is the correct thickness. However, I have never seen this...not sure how it performs

  5. Expert Member

    There has been a bit of discussion on GBA of possible workarounds, mainly to avoid buying sheathing during this period of high prices. I wonder if we are g0ing to look back and think that the savings weren't worth the reduction in build quality?

    1. jonny_h | | #8

      I wonder if there will indeed be a reduction in quality though. I guess what I'm getting at is -- are construction methods like diagonal board sheathing / subfloor, or thick T&G flooring without subfloor, actually lower quality? Or did they simply fall out of favor because the labor and materials savings of sheet goods were so attractive, a balance that has been temporarily(?) tipped due to global supply chain issues?

      I'm under no illusion that board subfloor, or thick T&G hardwood, will be a low-cost option -- but the cost of plywood may have made these options slightly more economical, or at least competitive, and I wonder if there might even be some benefits to the old approaches. I doubt that 5/4 T&G flooring is going anywhere!

      1. creativedestruction | | #9

        I wouldn't call diagonal board subfloor 'lower quality', it just fell out of fashion given the speed of 4x8 sheet goods. If you're supplying the labor it'll be slow going but results will be just fine. Screws, glues & rock n roll.

      2. Expert Member
        MALCOLM TAYLOR | | #10


        I wasn't so much speaking of your idea of using an alternative subfloor, as musing in general as to whether we might be making a mistake to re-think our practices based entirely on the current prices of materials.

        However, there are some advantages in using sheet goods as sub-flooring. Off the top of my head:
        - They form a shear diaphragm and help distribute loads.
        - They are an effective air-barrier.
        - They do not swell or shrink significantly with changes in moisture levels.
        - There is less waste during construction.
        - They can be cored or cut for services.

  6. Expert Member
    NICK KEENAN | | #7

    I lived for many years in a house built in 1870. The flooring was tongue and groove, true 1" thickness, no subfloor, nailed perpendicular to the joists, one nail through the tongue into each joist. If you didn't know how it was laid you'd never guess.

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