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Bouncing Floor

MarkVB | Posted in General Discussion on August 30, 2005 07:08am

I have a laundry room 6 feet by 12 feet that houses a side load Bosch clothes washer and dryer. There’s 3/4 inch tongue and groove subfloor glued to the joists. The joists are accessible from the basement. On top of the subfloor is a plastic try with drain should the washer spring a leak. The entire floor except the tray is is covered with 1/2 inch plywood glued down. And on top of that is 1/4 inch hardy board. I am tiling the floor and don’t want the grout to crack or tiles to lift. Sometimes, the spin cycle of the washer causes the floor to rumble a little. I don’t want to install posts in the basement because they would be located in the middle of a valuable work space. What can I do to reduce the floor bounce and protect my tile from cracking, grout cracking? Thanks, MarkVB

Edited 8/30/2005 12:10 am ET by MarkVB


Edited 8/30/2005 12:13 am ET by MarkVB

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  1. YesMaam27577 | Aug 30, 2005 03:17pm | #1

    What can I do to reduce the floor bounce and protect my tile from cracking, grout cracking?

    You can determine if the joists are sized correctly for the span, and for the allowable deflection that you desire. For most tiles, the deflection should not exceed 1/360 of the span.

    And if they aren't, then you can add blocking, or more joists, or a beam and some columns.

    There are on-line span charts to look this up -- I seem to have lost thelinks, or I'd include them. I'll bet that a Google search will find them easily.

     

     

    Unless you're the lead dog, the view just never changes.

  2. FastEddie | Aug 30, 2005 04:12pm | #2

    Why did you not remove the washer & dryer and install plywood over the entire floor?

     

     

    "When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it."  T. Roosevelt

    1. custombuilt | Aug 30, 2005 05:56pm | #3

      I'm wondering what eddy said too......?  Usually I Cover the whole floor with 3/4 plywood and screw down with 3 inch screws.  then i put my cement or hardibacker.  The 3/4 usually stiffens things up a lot.....then you could put some blocking below, if it still shook, post and beam

      Also wondering, you said the plywood is glued down.....how you screwed it down too! or else it doesn't help you much

      When in doubt, get a bigger hammer!

      Edited 8/30/2005 10:58 am ET by custombuilt

    2. MarkVB | Aug 31, 2005 03:56pm | #7

      I removed the dryer because that was easy. The washer was in a tray that was secured to the floor with a center drain connection. At the time, I didn't think I wanted to get into changing the plumbling under it to extend the drain connection 1/2 inch. Now I regret not doing that. Before laying the tile, I probably should just do it and glue down the 1/2 inch plywood and install a new tray. Thanks for the suggestion. MarkVB

      1. Piffin | Aug 31, 2005 05:13pm | #10

        I don't know that doing it now will help that much, since you will still have a break around the edges. The point of the ply is to spread the load over a larger span to involve more joists in the load sharing. Furring on bottom will help that too, but more plywood on top would have to spread across the area rather than breaking at the edges of the unit. 

         

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

    3. MarkVB | Sep 01, 2005 08:47am | #11

      This is a remodel job....placing Italian Porcelain tile on 1/4" hardy board over vinyl which is glued to 1/2 plywood which is glued to 3/4 inch tongue and grove underlayment which is glued to the floor joists.I removed the dryer. I left the washer in the tray and only then realized that the tray was really resting on the 3/4" tongue and grove underlayment. The remaining floor around the tray already had 1/2 inch plywood glued down. Taking out the tray and raising it 1/2" with plywood wouldn't help much because the underlayment insert (32 X 32 inches) would not be connected to the adjacent plywood. The 1/2" insert would be seamed on all sides. Hence, the vibrations from the washer during high speed spin cycle would not be distributed over the entire area - mostly on the tray area.

      1. Dave45 | Sep 01, 2005 04:59pm | #13

        "1/4" hardy board over vinyl"

        This could be an issue.  A few weeks ago, I replaced a tile kitchen floor that had been laid directly over the old vinyl.  Demolition was almost easy since much of the vinyl had never really adhered to the underlayment - lol.  Make sure you nail/screw your hardibacker per the manufacturers recommendations.

        I also had a flex problem with my own entry floor a few years ago.  Some blocking between the floor joists stiffened things nicely and the tile hasn't budged for eight years now.

         

        1. MarkVB | Sep 02, 2005 07:33am | #16

          Thanks Dave, I understand the benefit of blocking based upon what you wrote. MarkVB

  3. JeffSmallwood | Aug 30, 2005 06:42pm | #4

    http://www.johnbridge.com/vbulletin/deflecto.pl

    is the deflection calc that was mentioned earlier in the thread.

    1. MarkVB | Aug 31, 2005 04:15pm | #9

      I not sure how I would be able to calculate the deflection other than using charts available on the web. As it exists now, there is a total of 1.5 inchs of flooring that makes it level with the rest of the home and still leaves room for the exterior doors to swing in.3/4 inch tongue and grove plywood glued to joists
      1/2 glued on top
      Vinyl flooring 1/16 inch - removed any loose spots
      1/4 inch hardy board, with latex thin set screwed every 6 inches.The only potential problem is that the clothes washer tray is attached to the subfloor. Perhaps I should raise it at least 1/2 inch by gluing and screwing down plywood. Your thoughts?

      Edited 8/31/2005 9:16 am ET by MarkVB

    2. MarkVB | Sep 02, 2005 07:39am | #18

      Jeff, I really don't know the formula to calculate the floor's deflection. I went onto Google and most of what I found was for engineered wood. I have solid joists... no open trusses or I beams trusses. If you know the formula, I'd really welcome the informtion. Thanks, MarkVB

  4. sharpblade | Aug 31, 2005 03:33am | #5

    >>> And on top of that is 1/4 inch hardy board.

    I hope you set this in thinset before you screwed it down to the ply, right?

    1. MarkVB | Aug 31, 2005 04:01pm | #8

      Yes, I applied a latex thin set because I was going over inlaid. Thanks for the affirmation. MarkVB

    2. MarkVB | Sep 02, 2005 07:37am | #17

      Yep, latex thinset and screwed every 5-6 inched all ways. Thanks for the comment. MarkVB

  5. Piffin | Aug 31, 2005 06:22am | #6

    The plywood should have covered the whole floor to spread the load out and create a stable diaphragm for resisting vibrations.

    What you can do now is to sister up the joists from under and then run furring at 16 or 12 inches on center perpendicular to the joists down under at the cialing level.

     

     

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

    1. MarkVB | Sep 01, 2005 08:57am | #12

      What size furring strips? Thanks, MarkVB

      1. Piffin | Sep 01, 2005 09:30pm | #14

        1x4 or here, we get a product called strapping which is spruce 1x3 at actuall 3/4" x 2-5/8" with an eased edge 

         

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

        1. MarkVB | Sep 02, 2005 07:30am | #15

          Thanks. How do 1 X 4' nailed or screwed across the joists (perpendicular) reduce the springiness of the floor. I've heard about this before and don't really understand the physics. Thanks. MarkVB

          1. Piffin | Sep 02, 2005 07:43am | #19

            Two things. They function similarly to blocking or bridging.Load sharing is one. The lods placed on any one or two jioists is shared with their neighbors.Anti roll to keep joists upright so they can each do their job at their best. 

             

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

          2. MarkVB | Sep 03, 2005 12:45am | #20

            Got it and thanks. MarkVB

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