Why should a subfloor be screwed down?

Discussion in 'Flooring' started by acolic, Aug 2, 2019.

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  1. Aug 2, 2019 #1

    acolic

    acolic

    acolic

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    Hi

    I’ve installed a subfloor in my basement. Essentially it’s DeltaFL with a layer of T&G OSB on top.

    I’ve seen instructions that I should Tapcon each sheet of OSB down.

    Why? The floor is not going to shift. And why would I want to drill holes through the DeltaFL.

    Just wondering.

    Thanks

    Alex
     
  2. Aug 2, 2019 #2

    Gary

    Gary

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    What type of flooring do you plan to put over it?
     
  3. Aug 2, 2019 #3

    acolic

    acolic

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    Still being debated. Top options are:

    Cork flooring;
    Laminate flooring; and
    Engineered hardwood.
     
  4. Aug 2, 2019 #4

    Gary

    Gary

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    I just assumed best practice was to screw it down with sealer on the screws. I guess I never thought of going without. I'd be interested in the technical reason myself. I can see it if the flooring requires a stable subfloor, but if it's a floating floor covering???
    Since it's suggested it be screwed down, I'm sure there's a good reason. Maybe someone will stop by and let us know.
     
  5. Aug 2, 2019 #5

    Snoonyb

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    Who suggested it or was it a utube video without regard for the Delta substrate?
     
  6. Aug 3, 2019 #6

    oldognewtrick

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    I'm wondering why the need of OSB if your going over a substrate like concrete? What is under the Delta?
     
  7. Aug 3, 2019 #7

    acolic

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    It was a couple of YouTube and DIY websites.
     
  8. Aug 3, 2019 #8

    acolic

    acolic

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    The OSB was just extra for warmth. My last house had a subfloor made up of something similar to DeltaFL and OSB and it was quite warm.
     
  9. Aug 3, 2019 #9

    acolic

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    I forgot to add the DeltaFL instructions say to screw each sheet down with 6 screws. Drill a hole, add some silicone caulking and fasten the board down.
     
  10. Aug 3, 2019 #10

    havasu

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    Did you include a vapor barrier if you place that wood substrate directly on the concrete? In wet or moist conditions, it will turn into a breeding ground for mold.
     
    joecaption likes this.
  11. Aug 3, 2019 #11

    acolic

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    Yup I added a vapor barrier then the DeltaFL then the OSB.
     
  12. Aug 3, 2019 #12

    havasu

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    I just did this to level out my concrete floors before adding my vinyl plank flooring. I floated Mapei 995 adhesive and built in vapor barrier, then added 5/8ths OSB tongue and groove, and nailed it to the floor every 12" for rigidity and to secure properly to the glue. I then layed the planks throughout my house. 15648593331496488325950119368221.jpg
     
  13. Aug 4, 2019 #13

    Rusty

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    Mold can still grow under the vapor barrier. Most moisture in concrete comes from below. That is why I prefer floor coverings that can breathe. They allow the moisture to vapor off.
     
  14. Aug 4, 2019 #14

    havasu

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    True. It needs to be noted that this slab is on ground, not underground. For below grade, Rusty is absolutely correct. Let it breath, and do your homework on all exterior water run off to include all drainage to go away from the home.
     
  15. Jan 1, 2020 #15

    acolic

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    Happy New Year

    And after a year of no work in my basement I am back at it.

    It’s all painted just waiting for a floor to be installed.

    I’m back on the why I need to screw the OSB down and why I would put a hole in the vapor barrier question?

    Thanks
     
  16. Jan 1, 2020 #16

    nealtw

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    Maybe so it doesn't go bump when you walk on it and the silicone is to repair the hole in the VB
     
  17. Jan 1, 2020 #17

    Rusty

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    Some guys loose lay the subfloor, but I have never done it. They claim it works great.
     
    Last edited: Jan 3, 2020
  18. Jan 2, 2020 #18

    acolic

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    I just hate doing things without knowing why.
     
  19. Jan 2, 2020 #19

    Jeff Handy

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    If your subfloor system is tongue and groove, it should be able to just float.
     

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