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Help with floor thickness problem

JeffHeath | Posted in Construction Techniques on December 20, 2005 05:25am

Came over here from the Knots to get some help.  First off, Happy Holidays to all.

Since this isn’t a piece of furniture, I thought I would ask how to solve a problem I’m having.  I am rehabbing My Old House, and just started working on the oldest section of the original home.  It is a 24′ X 17′ room, and is on it’s own level.  It was the original kitchen, dining room/family room of the original home, and is now going to be my son’s bedroom/bathroom.  I gutted the room and finally discovered why the floor seemed so “mushy”.  The deck was made of 1/2″ plywood, most of it scraps nailed and fitted, not all in 4’x8′ pieces. 

Since this room has it’s own staircase, and is the only room on this level (split level), can I just put down 3/4″ plywood over existing floor without issue, or do I have to pull the 1/2″ plywood up first.  Losing 3/4″ ceiling height is not an issue, as it’s over 8′ anyway.  All doorways will be new construction when I’m finished.  Joists are 2 x 10 construction, 16″ OC, with a steel beam running down center in sub basement.  Floor is currently “a little” bouncy, but not any worse than any other part of this old house.

Thanks for your help.

Jeff

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Replies

  1. Lansdown | Dec 20, 2005 05:57am | #1

    The advantages of pulling it up, is that you can glue down your new ply directly to the joists. Having said that, I have put new subfloors over an existing if it was in decent shape and not pieced together.

  2. Brian | Dec 20, 2005 05:58am | #2

    Jeff, other than matching floor heights with trim etc, the only issue I see would be squeaking.  If I were confronted with the same issue, I'd use 3/4" osb, and liberal amounts of subfloor adhesive, screwed with long screws (9 per row) at every joist. 

    Leave the current subfloor in place - much less work than tearing it out.

    edit: actually I would use ring shank nails from the nail gun, but thats me...

     

    Treat every person you meet like you will know them the rest of your life - you just might!



    Edited 12/19/2005 9:59 pm ET by Brian

    1. JeffHeath | Dec 20, 2005 09:14am | #7

      Brian

      What adhesive would you use?  Would something like liquid nails work well, or is there something better that you guys use? 

      Also, I have a framing nailer.  Would ring shank nails be better than screws?  I definately don't want squeeks.

      Thanks, and Merry Christmas

      Jeff

  3. Piffin | Dec 20, 2005 06:05am | #3

    Other than those sqeaks they have mentioned, my thoughts go to the stair/steps entering this area. There should be no more than a 3/8" diference between any two riser heights in th esame flight to avoid creating a trrip/fall hazard.

    So say if there are three risers now, all equall, and you raise the lower floor an exrra 3/4" then the lowest riser will be too short and need rectification

     

     

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

    1. JeffHeath | Dec 20, 2005 08:48am | #6

      Piffin, and All:

      The stairs lead up to this area.  There are 5 total.  The stairs are a joke, and I was going to take them out and rebuild them, anyway, when the job is finished in the room.  At the top of the stairs is the entrance doorway to the room, which will have carpet.  The main floor which leads up to this room is our back entranceway and kitchen entrance.  The floor is going to be 3/4" Santos Mahogany, and I will be rebuilding the stairs, anyway, and creating 5 equal steps, so I don't think it will be an issue. 

      Taking up the old sub-floor was going to be a grizzly bear of a job for me, so it sounds like the construction adhesive and extra screws to hold the new flooring down, and help stop the squeaking is the way to go.

      Is good old liquid nails adhesive good, or is there something better that I should use. Thanks for the help on this one, and I'm sure I'll have a few more questions when I get to putting in the shower tub.

      Merry Christmas,

      Jeff

      1. Piffin | Dec 20, 2005 02:36pm | #8

        liquid nails is fine for hanging crown or sheetrock, but for structural there are far better adhesives in th ePL line, Used to use PL 200 or 400 but now all we use is PL Premium, a polyurethenme construction adhesive that practically welds things together, even in damp and cold. It expands slightly to fill voids so it fgoes further than regular, and is the strongest I have ever used. 

         

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

        1. JeffHeath | Dec 20, 2005 06:47pm | #9

          PL Premium.  Got it.  Where can this be purchased.  Is it available at one of the big boxes, or do I have to order it.

          Thanks

          Jeff

          1. Piffin | Dec 21, 2005 12:38am | #10

            I shop at real lumberyards so I don't know what big boxes carry.
            I'll bet the manufacturere coulod give you a hint who sells it retail thohttp://www.stickwithpl.com/http://www.stickwithpl.com/where/where.asp
             

             

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

          2. JeffHeath | Dec 21, 2005 04:16am | #11

            I found the PL Premium.  Last question, is 3/4" OSB T & G good, or should I use plywood.  Thanks again in advance.

            Jeff

          3. Piffin | Dec 21, 2005 04:49am | #12

            I favour Advnatec over either, but any of the above would do for your application 

             

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

          4. Brian | Dec 21, 2005 05:16am | #13

            OSB is good stuffTreat every person you meet like you will know them the rest of your life - you just might!

          5. Piffin | Dec 21, 2005 05:29am | #14

            for what? 

             

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

  4. andybuildz | Dec 20, 2005 06:07am | #4

    Ditto on leaving the floor down then gluing and screwing the new 3/4" sub floor to the existing after cleaning it nicely. Using Advantech T&G would "really" be a really nice job!

    Be well and happy new year

    andy

    The secret of Zen in two words is, "Not always so"!

    When we meet, we say, Namaste'..it means..I honor the place in you where the entire universe resides, I honor the place in you of love, of light, of truth, of peace. I honor the place within you where if you are in that place in you and I am in that place in me, there is only one of us.

     

     


     

     

  5. DanH | Dec 20, 2005 06:09am | #5

    Yeah, an issue is the stair riser height. I think there's a special exemption for the first and last step, but you'd be advised to double-check that.

    If ignorance is bliss why aren't more people

    happy?

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