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  1. #1
    Join Date
    May 2012
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    4

    Question Leveling floors, removing old subfloor

    Hi,

    I need an advice. We just bought 100 yrs old house, everything in the basement seems to be straight, however second and third floors are sagging in the middle (about 2-3 inches), after talking to several engineers/architects nobody seems to be able to pinpoint the problem and all they say that the house is old and it's natural. I still want to level the floor, I removed thin hardwood and it looks like I have 3/4 planks as a sub floor, on the third floor somebody actually laid hardwood right on the joists without a sub floor, and in the bathroom I have about 5 inch of concrete.

    So I am planning:

    1. install 1/2 inch plywood on top of the sub floor on the 2 nd floor leveling with planks and shingles, does it make sense? would it be better to remove sub floor and replace it with plywood?

    2. remove hardwood on 3 rd floor, install plywood sub floor and then put hardwood, does it make sense? would installing sub floor add much weight?

    3. remove concrete floor in the bathroom on the 3rd floor and install plywood with cement boards, existing concrete is cracking on joists and I can probably fix it but I think if I remove it I'll reduce the weight it puts on the house.

    Any suggestions, opinions welcome.

    Thank you.

    Viktor.

  2. #2
    Join Date
    Dec 2010
    Location
    Houston Texas
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    2,509

    Default Re: Leveling floors, removing old subfloor

    Victor,

    The joists are sagging because they were undersized and too far apart from the original construction. Just like my house. To fix this its best to;

    1- Calculate the current deflection of your joists. To do this you'll need to know the joist size, span, and spacing. You want at least L360 for tile, which will make your floor feel firm enough to stay where you want them.

    2- Sister the joists or add more joists to get the desired deflection

    3- Replace the flooring as desired.

    As for the bathroom, head on over to the John Bridge TIle Forum for speedy, detailed answers, pictures, and an extensive library.
    Last edited by HoustonRemodeler; 05-24-2012 at 12:43 AM. Reason: poor spelling

  3. #3
    Join Date
    May 2012
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    4

    Default Re: Leveling floors, removing old subfloor

    Hi,

    Thank you for your answer, I'll try to do the calc, but the problem is that joists are actually rather straight, the sag is happening across the joists i.e. joist near exterior wall is higher than a joist in the middle of the house, I also have a chimney on the wall that is higher. I realize that it sounds that house should look crooked outside, but it is actually straight. Also the ceiling on the first floor is almost straight. The house had some renovations around 30-40 years ago and they leveled floors in the bathroom and they are still straight, there's no cracking although walls and ceiling have old plaster. Based on this, do you still think it's better to try to adjust joists?

    Thank you.

    Viktor.

  4. #4
    Join Date
    Dec 2010
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    Houston Texas
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    Default Re: Leveling floors, removing old subfloor

    depends on what you mean by 'adjust'

  5. #5
    Join Date
    May 2012
    Posts
    4

    Default Re: Leveling floors, removing old subfloor

    Hi,

    I mean second floor has several walls sitting on the sub floor. I am not sure if you are suggesting to do the sistering room by room? In this case I would have to cut sub floor in pieces and it would not be straight as the areas under the walls would still be lower. If I am to do this for the whole floor than I would have to pretty much destroy all walls, which sounds a bit excessive considering that I don't see any evidence that the house has moved in the last 30-40 years and all I want to do is to level up the floors a bit. Does it make sense?

  6. #6
    Join Date
    Dec 2010
    Location
    Houston Texas
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    Default Re: Leveling floors, removing old subfloor

    You can also sister the joists by removing the ceiling below and adding to the joists from supporting wall to supporting wall.

  7. #7
    Join Date
    May 2012
    Posts
    4

    Default Re: Leveling floors, removing old subfloor

    Hi, thx for replying, however even if I remove ceiling on the first floor, the only two options I have to level the second floor are to jack up lower joists or cut subfloor on the second floor near supporting wall, which one were you suggesting?

    I am just trying to understand if the house is not moving anymore, what's wrong with simply adding planks on top of joists and covering with plywood room by room?

    Thank you.

  8. #8
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,441

    Default Re: Leveling floors, removing old subfloor

    katvik,

    Let me try to explain it: if you have a slab of concrete that sags on one end, do you:

    (a) pour more concrete on top of the existing concrete to level it, or
    (b) cut out the sagging concrete, regrade, recompact, remove any water pipes from under the concrete and then pour new concrete.

    If you answered (b), you are correct.

  9. #9
    Join Date
    Dec 2010
    Location
    Houston Texas
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    Default Re: Leveling floors, removing old subfloor

    If the joists sagged, they are continuing to sag. At the very least they will bounce with every step.

    You can add more wood to the top if you'd like. Its your house and your money. You'll succeed in adding more weight to the floor without fixing the problem, only the symptom.

    To correct the problem the joists need to be sistered properly or jacked back up and supported from underneath. Which you choose and how you accomplish it is between you and your wallet.

  10. #10
    Join Date
    Jan 2008
    Posts
    1,337

    Default Re: Leveling floors, removing old subfloor

    Quote Originally Posted by HoustonRemodeler View Post
    If the joists sagged, they are continuing to sag. At the very least they will bounce with every step.

    You can add more wood to the top if you'd like. Its your house and your money. You'll succeed in adding more weight to the floor without fixing the problem, only the symptom.

    To correct the problem the joists need to be sistered properly or jacked back up and supported from underneath. Which you choose and how you accomplish it is between you and your wallet.
    What the OP wants to do is 'patch' and hide the problem, but this is the fix. What's the difference? The cost, of course, and the fact that a fix happens once while a 'patch' will keep giving trouble. If the floor line isn't straight at the ends perpendicular to the joists, you will want to shim then after you reinforce and straighten the joists. Glue the shims to the joists and let the glue dry before laying the subflooring or they may split and fall out later on. If you're going to bother with this at all then fix it right.

    Phil

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