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  • Subfloor flatness

     Chuck updated 1 month ago 2 Members · 5 Posts
  • Chuck

    Member
    August 6, 2021 at 3:40 pm

    Joe,

    I’ve removed carpet and other flooring from my living room, dining room, and kitchen. My main question relates to the living room. I’ve attached a marked up layout of the room illustrating the subfloor (non)flatness. The subfloor is 1/2” particle board on top of 5/8” plywood, with joists running north/south and resting on an east/west beam down the center of the house.

    In order to get an accurate picture across the 24’ x 27’ L-shaped area, I shot a laser line from wall to wall set at the same height on both walls, and then I measured the floor’s deviation every foot along the beam. Those are the green lines on the picture.

    My biggest concern is area #1 in the living room. When shooting east/west across the joists, I get a trough that’s up to 5/8” deep in the center and runs left/right across the room. I think I could bridge the area with a 12’ screed, but that seems like an awful lot of material. Is that the right approach?

    Shooting north/south across the areas (along the joists), there’s minor deviation, but it’s flat enough to deal with the small spots easily, I think. I’m not showing the dining room & kitchen results on the layout.

    The red areas represent humps in the subfloor, but it looks like those should sand down relatively easily.

    Does what I’ve described make sense? If so, do you have any particular suggestions for handling it apart from lots of thinset?

    Thanks

    Chuck Royalty

  • Joe

    Administrator
    August 7, 2021 at 8:06 am
  • Chuck

    Member
    August 7, 2021 at 2:45 pm

    Joe- Thanks for your fast response. I neglected to include some of the background you need – after all, I’m familiar with what I’m doing ;-). I asked the question about the undercutting the hearth a while back, so this is the same project. I’ve attached the layout from that in case it helps. The partial layout I sent earlier is rotated 90 degrees from the whole upstairs layout.

    In answer to your question about the direction, I need to run the plank east-west in order to make the transitions between living room / dining room & dining room / kitchen work. So that leaves me looking at doing something with the subfloor, and replacing the particle board looks like the route I might need to go.

    Before settling on that, though, I have a couple of questions. Would it be possible to lay plywood on top of the particle board – basically saving having to tear up & then replace the half inch of wood? So I’d be using, say, 7/16, 3/8, & 1/4 layers on top instead of a lot of thinset. And to reduce the chance of the particle board soaking up water & swelling, would it help to seal it with something? The particle board seems to be in good condition, given that it’s 42 years old.

    I haven’t discussed the dining room yet, but years back oak parquet was replaced with bamboo, and the installers appear to have made heavy use of thinset (up to 1/4″) to level that floor. I’ve chipped up some of that to clean things up, and the particle board underneath looks to be in good condition. I wonder if it’s because of residual glue or just that they got lucky.

    If it would be easier to discuss this on the phone, or if you need photos or other info, I’m glad to do that. I appreciate your insight into the … situation I’m facing.

    Chuck

  • Joe

    Administrator
    August 9, 2021 at 8:22 am
    • Chuck

      Member
      August 15, 2021 at 7:46 pm

      Joe-

      Thanks for the feedback. Sorry for the delayed response. We put things on hold temporarily in order to make a quick trip to Canada, since we hadn’t seen our daughter-in-law in something like forever. I think I’ll go with building up the worst areas with plywood, and then fill in the edges & any remaining dips with thinset. I’m more comfortable working with wood than concrete, and that seems like a good compromise. I don’t think a phone call is needed, but I appreciate the offer. Feeling much more comfortable about it now.

      Thanks

      Chuck

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