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Thread: Spongy floors

  1. #1
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    Question Spongy floors

    I plan to install hardwood floors in my new house. The subfloor is 3/4 OSB on manufactured I beams. I noticed when someone walks on the floor you can feel the floor move through out the room. Will this damage the hardwoods I am installing? I am thinking of adding support to the floor but donít know if I should install an extra layer of OSB board on the original subfloor or install 2x2 cross supports between the I beams joists like they do with 2x10 joists?

  2. #2
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    Default Re: Spongy floors

    Quote Originally Posted by fuehrer View Post
    I plan to install hardwood floors in my new house. The subfloor is 3/4 OSB on manufactured I beams. I noticed when someone walks on the floor you can feel the floor move through out the room.
    You are experiencing what is usually referred to as "bounce" which is the up and down flex of the floor system. Even with the 3/4 OSB and the I joists there still can be bounce depending on the span and the spacing of the joists.


    Will this damage the hardwoods I am installing?
    Not really but you may find the fasteners ( nails or staples ) might work loose from the hardwood and causing squeaks in the floor. This may be more likely since OSB doesn't hold fasteners as well as plywood. I guess the worst case being if the planks become too loose the tongues may be damaged.


    I am thinking of adding support to the floor but donít know if I should install an extra layer of OSB board on the original subfloor or install 2x2 cross supports between the I beams joists like they do with 2x10 joists?
    If you do add another layer of sub floor a suggestion would be to use plywood screwed through to the joists. The plywood will hold fasteners better than OSB.
    Just remember if you decide to add another sub floor consider how much it's adding to the overall height to the floor with the hardwood on top.

    With I joists adding 2x2 wood "X" bracing is something I wouldn't use ... there are metal bracing available for these types of joists. The tops of the joists are tied together by the sheathing of the sub floor and the idea of "X" bracing is to help with the bottoms of the joists from moving side to side and only provides a little help with the up and down flex. In cases simply attaching 1x3 or 1x4 strapping every 4 feet to the bottoms of each joist ( tieing them together ) will help similar to the "X" bracing.

    If you want to really stiffen the floor use plywood glued and screwed to the sides of the joists from the top web to the bottom web.... almost creating a solid beam. This would be done the entire length of each joist. Then attach full height cross blocking to each joist at least every four feet of span. This will help a lot though it may not eliminate the bounce completely it will stiffen the floor and because they are solidly attached to each other will allow the floor to flex as a single component rather here and there. This is one method to stiffen floors that will have tiles and would make a difference for your situation.

    Hope this helps.
    Last edited by canuk; 11-06-2007 at 08:46 PM.

  3. #3
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    Red face Re: Spongy floors

    It does the same thing in my kitchen where I'm installing Travertine on the floor. I thought with the under layment and weight of the stone it wouldn't be an issue.

  4. #4
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    Default Re: Spongy floors

    You didn't mention the spacing of the floor joists. If the joists are 24" on center you should have used at least 1" OSB or plywood. I prefer plywood glued and screwed to the I beams. Installing 3/4" hardwood will stiffen them up quite a bit.
    Jack
    Last edited by JLMCDANIEL; 11-06-2007 at 04:16 PM.
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  5. #5
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    Default Re: Spongy floors

    Quote Originally Posted by fuehrer View Post
    It does the same thing in my kitchen where I'm installing Travertine on the floor. I thought with the under layment and weight of the stone it wouldn't be an issue.
    If you have " bounce" in the floor putting more weight on top won't help .

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