Nails or Screws for Attaching Underlayment

Discussion in 'Floor Preparation' started by mauibumm, Apr 9, 2009.

  1. mauibumm

    mauibumm Member

    I have yet another question. When ever I read about attaching a plywood underlayment to a subfloor it talks about using nails. I can't find any instruction or installation guidelines that note using screws.

    I have read on this forum that it is possible to utilize screws but I don't understand why all the direction leave out using screws as an option.

    I will be using a 3/8" plywood over a 2x6 TG subfloor if it matters.

    Is there an advantage to using nails. Can I get away with screws? Is the fear of screws that they will be over driven????
  2. Jim McClain

    Jim McClain TFP Owner/Founder Administrator

    Some of the problems with screws is the heads - they sometimes don't get driven flush, they break when being driven through denser materials or they get over-driven. Nailing (ring shank, non-coated, long enough to go through underlayment and well into subfloor) or stapling (1/4" crown, divergent points, long enough to go through underlayment and most of the way through subfloor) is the acceptable method and economical to boot. With a floating floor, you don't have to worry about the dents a hammer head makes, but they can be filled easily with patching compound for other types of flooring (like vinyl, etc.). Staples generally don't need to be patched, but you do need to make sure they are flush with the surface - not over-driven either.

    Remember you are dealing with a thin piece of plywood. The screw head would tax the thickness of the plywood quite a bit, but the nail head not so much. A staple, even less (in 18 gauge).

    I'm sure there are other pros who like the screw, but I never found the benefits worthy of the effort and possible liability (screw heads might not break immediately). But regardless of what you use, the fastening schedule (how many fasteners per) should be adhered to.

  3. stullis

    stullis Charter Member Senior Member

    Use a narrow crown stapler.
    Rent one or better yet hire a pro to install your underlayment.
  4. kwfloors

    kwfloors Fuzz on the brain Charter Member Senior Member

    Years ago Armstrong had a ulay guideline sheet on how to fasten the plywood to the floor. They said nailing with ringshanks no deeper than what you are nailing to or a mallet driven stapler. We also got a recommendation sheet on how much to nail a particular thickness of plywood to the floor from Plum creek which is our local mill. They had it down to how many nails to use. I use a 1/4 inch air stapler and am very picky on how to use it. You have to hold the sheet down with your foot and staple next to it to have the sheet tight to the floor. You can use screws but don't use any that are oiled and don't break any when you suck them down or else you have to get it out and drive another one.
  5. Kman

    Kman Tile Expert I Support TFP Senior Member Published

    I don't use nails, but I also don't put down anything less than 1/2". A ring shank or screw shank nail would work fine. You could probably rent an air nailer pretty cheap for the weekend.

    One note on KWfloors advice, I agree that you have to hold the ply down with your foot, just make sure you don't nail too close to your foot. If you accidently hit a nail in the subfloor, the nail you're shooting could curl up and end in your foot, I've seen it happen.

    Also make sure that your nails actually hit the subfloor and don't go between the planks.
  6. mauibumm

    mauibumm Member

    Thanks, for the advice. I will have access to a stapler, a nail gun, or a screw gun. What I don't own my neighbor will have.
    I am just trying to figure out what is the best method to secure the underlayment. I am not looking for the fastest or the cheapest, but the best. Perhaps there is no difference ???? When I discuss this with everyone locally they tell me to use screws. Their impression is that the screws are more secure and will adhere better. I get the impression they believe the nails may loosen or back out over time making the board loose or more susceptible to squeaking.

    I was thinking of using screws based on what everyone told me, but looking up the installation instructions it only mentions nails or staples.
    From what I gather on this board the method of attaching it probably doesn't ultimately matter so long as it is done properly (ahh and that screwing them is an acceptable method).
  7. rusty baker

    rusty baker Well-Known Member

    Professionals flooring installers use a stapler. It holds better and gives you a smoother surface.
  8. Barry Carlton

    Barry Carlton I Support TFP Senior Member Published

    Staples are coated usually, increasing their holding power.
    Staples are usually either convergent (meaning the 'legs' pull together as they are driven in), or divergent (meaning the 'legs' spread apart as they are driven in) thus, increasing their holding power.

    That and they are usually less expensive, faster, and easier than nails or screws.

    Many pros to using staples and few cons.

  9. mcbrides

    mcbrides Canadian Installers Senior Member

    Whether you screw, nail or staple your 3/8ths underlayment depends completely upon what flooring product you are planning to put over it. The purpose of an underlayment for vinyl is to have a glass-smooth surface to glue to (1/4 ply is the industry standard), whereas an underlayment for ceramic tile is to add strength (and 3/8ths isn't thick enough). Nevertheless, we would only fasten either 1/4 or 3/8ths with subfloor staples, 4" apart in the field, 1" apart on the seams, make sure to stagger the corners and do not use ripped edges anywhere but at the perimeter.
  10. Daris Mulkin

    Daris Mulkin The One and Only Charter Member I Support TFP Senior Member

    One of the problems with screws is that once set tight there is no give and take with the movement of the house in weather changes and such. It could cause the heads to shear off. Nails or staples are the best choices.

    My opinion and I'm sticking to it-maybe.

  11. mauibumm

    mauibumm Member

    "My opinion and I'm sticking to it-maybe."

    That was funny!
  12. Kman

    Kman Tile Expert I Support TFP Senior Member Published

    If I was going to use nails I would use a ring shank or screw shank nail. They have much better holding power than regular nails. Did I mention this in an earlier post? :hmmm: Sorry, senility setting in fast. :help:
  13. kwfloors

    kwfloors Fuzz on the brain Charter Member Senior Member

    3/8ths isn't thick enough? I see 1/4" and ditra mat all the time. Make sure the staples are close to the edge of the sheet, no farther that a strong 1/8" from the edge and you can't have too many.
  14. what are we installing over this plywood? Im just curious!
  15. Barry Carlton

    Barry Carlton I Support TFP Senior Member Published

    Laminate flooring.
    And for her purposes I think she decided on Halex 4X4 9mm sheets.

  16. stullis

    stullis Charter Member Senior Member

    1/4" ply is not considered structural. 3/8" is structural for ceramic.

    They are installing laminate and in this situation they really don't need to add any UL. All it will do is accentuate the uneveness of the joints if they do not sand the joints prior to installing the UL. Once they sand the joints they then won't need the UL. :rolleyes:

    Screws will hold better than staples or nails but you have to use the proper screws or you will have heads popping off. Dry wall screws are not what you use. ;)
    Also they don't hold significantly better and again in this situation other fasteners would be the fastner of choice.

    Whatever fastener you use you need to follow the fastening schedule for the thickness of the plywood and the intended us of the panel.
  17. Barry Carlton

    Barry Carlton I Support TFP Senior Member Published

    I couldn't agree more!!!! But ultimately this is the homeowner/DYI's decision.


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