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Installing Underlayment Questions

geoffharris | Posted in Construction Techniques on February 9, 2007 05:40am

I am installing underlayment for a hardwood floor over very old squeeky 5/4 x 6 planks.  I have a few questions that I need answers to:

1:  What size wood, type wood species would work the best?  I think Tongue and Groove 3/4 plywood installed with screws.

2:  What size and type of screws are best to use?

3:  How do I prevent squeeks?  Before I shoot the new underlayment down, I am going to throw 2″ drywall screws through the old planks to reduce the amount of squeeks.  In between the planks and the new underlayment, I am using PL-400.

4:  I know between the underlayment and the hardwood floor to use rosin paper, but what about in between the underlayment and the old planks?  And if I should put it between those 2, what side of the paper should I put the Pl-400?  Both sides or none at all?  Rosin paper or felt paper?

Thanks for your help.

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Replies

  1. calvin | Feb 09, 2007 05:54am | #1

    Why are you going to put down another layer over the subfloor?

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    1. geoffharris | Feb 09, 2007 06:32am | #3

      The old floor is around 50 to 60 years old.  The floors' nails are pulling up and the entire floor is extremely squeeky.

  2. Piffin | Feb 09, 2007 06:03am | #2

    I doubt you would need 3/4" for this. 7/16" or 1/2" should do it. If 3/4" is needed for strength, thenyou probably need to be tearing up that old planking anyhow.

    There is pine 1/2"underlayment made with a wax on the edges so it is less likely to sqeak itself.

    Forget teh drywall screws. They are made for drywall and will cause you grief on a floor. Use structural screws. for 5/4 palnks, the screws should be 2-1/2" to tighten to the joists. That should eliminate half your squeaks.

    Then with using enough glue and screws to fasten the underlayment to the subfloor, you are likely to eliminate the other half of them.

    You can leave one sqeak in the wholefloor just becaue...

    It'll keep the mice from being lonely.

     

     

    Welcome to the
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    Excellence is its own reward!

    1. geoffharris | Feb 09, 2007 06:35am | #4

      Piffin,

      It's not for strength, it's to reduce all of the squeeking.

      Does the pine underlayment with wax come in tongue & Groove or is it Square Edge?

      Thanks for the help with the structural screws.

       

      1. Piffin | Feb 09, 2007 03:31pm | #5

        square edge. 

         

        Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

  3. Danno | Feb 09, 2007 04:22pm | #6

    I agree with what Piffin said. Definitely no drywall screws. Use deck screws or possible ring-shank nails in a nail gun. Glue will help keep it from squeaking. I've also heard of isolating the new sub-floor from the old using rosin paper. Make sure old floor is secured to joists--screws (and construction adhesive if you can force some between the planks and the joists--also sometimes shims driven in will tighten things up and stop that from squeaking). I guess if I used rosin or felt (don't really know which is better, but just feel that rosin paper would slip better and make for less sqeaks) I wouldn't use glue (between the new sub-floor and the old planks). Seems like I even remember talk of using two layers of rosin paper so it really can slip.

    Piffin has more experience with this, so listen to him--I am sort of just thinking out loud.

    1. Piffin | Feb 09, 2007 04:30pm | #7

      This is not one where I would use a slip sheet.Half his noise is coming from plank to plank wood rubbing each other as it moves up and down under foot. The other is at the joist connection which he can secure with the screws.but to stabilize those edges together, he needs to glue the planks to the plywood above. I'd be running a bead every six inches or closer, and then fastenening down with ring shanks at 4"OC or screws at 5-6" OC.Thgat way, the planks down beneathe and the plywood underlayment become "As One" and are less subject to movement.With resin paper, you eliminate squeaks between old and new, but not the existing squeaks between planks. 

       

      Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

      1. Danno | Feb 09, 2007 04:41pm | #8

        What you say makes sense--is there anything he could spray between the planks to stop their qseaking (I suppose onde everything is screwed and glued, there will be no movement to make squeaks). I have heard of talcum powder, but would imagine it would work it's way out after a while--dry slide?

      2. tealwood | Feb 10, 2007 12:04am | #9

        I agree with your assessment that the goal is to make the new and old subfloor become  one.  Two questions:  one, when fastening the field area (i.e. not over the joist) should the screw or nail penetrate through the bottom surface of the old subfloor or sized so it doesn't?? and two, since it is an underlayment for a new wood floor wouldn't the new subfloor having a greater thickness (i.e. 3/4" vs. 1/2") provide better holding power for the fasteners of the new finished wood floor??

        Thanks for your thoughts............

         

        1. Piffin | Feb 10, 2007 02:29am | #11

          I guess to decide all that, I would wantto see what is there now. calvin and Beckman would be taking the old subfloor up I think and laying in 3/4" . I've done both ways dependiong on what condition the existing is in. How to remove from under the walls is a problem sometimes if taking up the old...But in general, the nails should go clean through the old in the field.You mioght have a point on that last line about holding power. 

           

          Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          1. TomC | Feb 10, 2007 06:26am | #13

            You mioght have a point on that last line about holding power.

            1/2" with 5/4 under, you have more than enough meat for the cleats of the finished floor.

            Just throw in my 2 cents, should take into consideration of the finished floor height as well.

  4. User avater
    RichBeckman | Feb 10, 2007 01:41am | #10

    I would just remove the old subfloor. It is a variable you don't need.

    Rich Beckman

    This signature line intentionally left blank.

  5. vinniegoombatz | Feb 10, 2007 05:36am | #12

     

    just gun ringshanks thru the old planks to quiet it down     ply adds lotta weight, skip it     use plenty of 2 inch fasteners on floor    u dont say if planks are laid diagonal across joists   if they are, ok    if perpendicular to joists, flooring haz to be laid on diagonal to joists over the planks    if both planks and flooring are perpendicular to joists, the flooring will open up on the long seams, or use plywood over the planks to solve that

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