Large subfloor gap. Need expert opinions please.

Discussion in 'Floor Preparation' started by V-Unit952, May 6, 2014.

  1. V-Unit952

    V-Unit952 New Member

    I'm in the process of having a home built and when I stopped over to take a look at the progress, I noticed a 7/8 in gap between two of the sheets of subfloor in one of the upstairs bedrooms. The gap runs for 4 feet and is in the middle of the room. I was a little concearned about it being that is seemed pretty wide, and ended up bringing it to the builder's attention. After some back and fourth, they agreed to have the gap caulked prior to the carpet and carpet pad being installed Does this seem like the proper remidy for a gap of this size or should something else be done? If caulk is the correct approach, do I need to be concearned about the type of caulk they use (sillicone vs. polleurothane)? I live in Minnesota where it can be cold in the Winter and humid in the Summer, so I'm assuming a small gap in the subfloor material is necessary for expansion, but 7/8 in seems pretty wide. I just want to make sure that the floor doesn't start creaking down the road because of it, or a divit starts to form in the carpet. The carpet is set to go in in a few days, so any advise you can give would much appfeciated. I've included a picture of the subfloor in question. The measired gap os 7/8 in by 4 feet.
     

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  2. Kman

    Kman Tile Expert I Support TFP Senior Member Published

    My first question would be, what are the joists made from? Are they 2x's, are they engineered I-joists, or are they floor trusses that are about 3" wide, maybe more?

    If they're 2x's, I'd want a section of that subfloor taken out and replaced to correct that problem. There's not enough width in a 2x to allow for a gap that wide. At best, you'd have 5/16" for each sheet to set on the joist, which just ain't enough to nail/screw into.

    If they're engineered and wider than the standard 2x joist, I might still want at least one side pull up where I could see how much surface the plywood has to sit on. You really don't know without pulling one up.

    Heck, how'd they even get a gap that wide to begin with? :hmmm:
     
  3. Jim McClain

    Jim McClain Owner/Founder Administrator

    If that is an end seam that is supposed to sit over a floor joist, I would be concerned that there is enough "meat" of the panels being properly supported by the joist on both sides. If it's a standard 2x joist, they are only 1½", which means one or both sides of the subfloor may be resting only a fraction of an inch on the joist.

    If I were building that place, I'd think, oops, there's a mistake I need to fix. My first thought is to cut a section of subfloor out on each side of that seam - if the joists are 16" OC, then that means a cut centered over each joist approximately 16" from that seam. You might even have to add a couple of 2x blocks to support the sides of a new section of subfloor panel. Then cut a new panel 48" x 32" (aprox), glue and screw it in place. THAT is how you fix it, not a glob of caulk that has no structural integrity at all.

    You just can't be assured that both sides of that seam is supported adequately. Unless you got x-ray vision, V-Unit952. ;)

    Jim
    PS: oh, looks like teh Kman posted as I was composing. Great minds... :)
     
  4. Kman

    Kman Tile Expert I Support TFP Senior Member Published

    To build on what Jim posted: In a subfloor repair, which this has the potential to be, you never want the patch to span two adjacent joists. You want it to span three joists at a minimum, i.e. one on each end of the patch and one in the middle.

    And you would definitely need something to couple the joints that run perpendicular to the joists where the tongue & groove has been compromised, as well as any other cuts running in that direction. I like to use 2x material for that, but I know others like to use 3/4" plywood.
     
  5. V-Unit952

    V-Unit952 New Member

    Wow, thanks for the quick responses guys! The builder uses I joists which are 2 1/2" wide and are 16" OC. I will contact them and see if I can get them to pull up the sides of the plywood to see how much of the joist has been hit. Anything else I need to be looking for when I'm over there?
     
  6. Bud Cline

    Bud Cline Tile Expert Charter Member Senior Member Published

    I would be curious to know how thick this subfloor material is and is it "tongue and groove" as it should be? Not seeing tongue and groove in that gap.
     
  7. federer

    federer Well-Known Member

    this subfloor doesnt look to be plywood?
     
  8. Jim McClain

    Jim McClain Owner/Founder Administrator

    It is OSB - Oriented Strand Board.
     
  9. federer

    federer Well-Known Member

    wow you are like superman.

    plywood is better than osb right
     
  10. Jim McClain

    Jim McClain Owner/Founder Administrator

    Depends on the plywood, but generally, yes. And I ain't anything like Superman - not in terms of flooring or anything else. Maybe closer to the Flash - I just answered what most pros know faster than anyone else. But there is so much I don't know about flooring. What I do know is miniscule compared to the collective knowledge of the pros that make this a community. I only got them to come together in this website, which happens to be 8 years old today. [​IMG]
     
  11. federer

    federer Well-Known Member

    you know, i was wondering about Bud's signature.


    hooray! i think a birthday gift should be more ads. or something to monetize it more. it will benefit the members too....say instead of researching outside, we can have vendors come in and showcase their products. everyone wins?**


    **just my opinion dont ban me please
     
  12. Kman

    Kman Tile Expert I Support TFP Senior Member Published

    If that's a joint that runs directly over the floor joist, there won't be a T&G joint there. They run perpendicular to the joists.

    If there was one there, then it would be cause for concern. :eek:
     
  13. Bud Cline

    Bud Cline Tile Expert Charter Member Senior Member Published

    Huh?!?!?
     
  14. Jim McClain

    Jim McClain Owner/Founder Administrator

    Subfloor panels are unsupported on the long side, not the short ends - unless they are not T&G, in which case, blocks need to be added to the joist structure to support the long sides between each joist.

    In other words, be worried if there is no joist under the 48" width of the panels. Be worried if the panels are not T&G and there are no supporting blocks along the sides either.

    Jim
     

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    Last edited: May 7, 2014
  15. Kman

    Kman Tile Expert I Support TFP Senior Member Published

    I mean it looks like that's a joint that lies over a joist, so there's no T&G there. If there was a T&G over the joist, then the panels are run in the wrong direction.

    For whatever reason, they took advantage of the fact that the joists are 2 1/2" wide and left a gap there. Still haven't figured out why they did that.
     
  16. federer

    federer Well-Known Member

    this is one reason why i want to diy the new floors. this stuff is unacceptable
     
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