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I'm first time homeowner and bought a house (built in 1999) in fall of 2015 (Philadelphia suburb). During inspection of the house I noticed squeaky floors and inspector said its due to nails rubbing against the joist making the noise and its minor issue.

The other day I was in the basement (unfinished) to check floor sections which squeaked the most. Just out of curiosity I put 4 feet level at the bottom of the joists (across joists) and to my surprise there were gap between joists and the level (for the most joists I checked) - it range from 1/8 to 1/2. I don't see any sag on length of the joists but level is off across the joists. Joists are resting on sill plate and its in good condition (no rotting or anything). Joists are 2X10 (not engineered joist) and they do not span more than 16 feet. To me it seems like joists are of different height/depth. When you look at the cross section of the joist - it appears they have bend slightly (like forming letter C if you see the end of joist - but very slight). I don't see any signs of house settling, basement is poured concrete and no cracks or anything like that. Basement is currently dry but I'm not sure if previous owner had any moisture issue in the basement in past or not (although quite elaborate battery backup sump pump for unfinished basement may be due to some water issues in past, will find out in spring). Floor sheathing is 3/4" (i think plywood and osb). Most of load bearing walls (like second floor wall) tend to line up against perimeter of the foundation or the metal beam that passes through middle of the basement.

We started notice that some section of the main floor is uneven and we are observing similar issues on second floor as well (first floor and second floor unevenness do not match). I'm guessing its due to joists of having different height. In general house is leveled - inspector checked with level at few spots. I checked with 4 feet level and found some high and low spots on the floor (may 1/8 to 1/4 hi/low spots) and those spot run across the joist.

  1. Is there any way to fix this? Is this a very serious issue - like house is falling apart - this is my first house so I don't know what's normal and what's very serious issue. I know foundation settling is a big issue and I ask inspector to check on it during house purchase process and he thought house foundation and framing is pretty sound (what ever his opinion worth...).

  2. Most of the house is carpeted - so I was thinking about using those squeak end kit (where you drive the screw in joist and take off the top part). But with uneven joist - would it make the floor even more uneven? Is there any other way to stop squeak?

  3. Carpet in some area is really bad and I thought I would install laminated floor in near future. But with uneven floor I don't think it will work well. what would be best flooring option for uneven floors (other than carpet and vynal)?

  4. I'm not in finical situation to hire a contractor or a structural inspector to access the situation in near term, if this is a serious issue what time frame I should consider to address it?

Thanks in advance.

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Dimensional lumber when green can vary in size depending on the day it is cut as it dries it gets worse because some beams are tighter grain than others. Since you have good access you could shim the areas that have the squeak with wood shims. Put some gorilla glue or wood glue on the shims and slide 1 in from either side. Don’t drive them in two far or the squeak will move. This is normal for dimensional lumber joist. Many builders now use LVL I beams to create a squeak less floors. By taking a few hours and shimming the gaps your floors will feel solid and the cost is minimal. If you screw down without the shims the problem will get worse and your floor will show the uneven surface.

  • Thank you. For some joist gap between sheathing and joist is such that I can insert shim (narrow part of the shim). But for the majority of the joists - gap between joist and sheathing is very narrow - in that case should I drive the shims with some force in to the gap? – bob Feb 19 '16 at 15:57
  • You can drive them but not much or it will make a new loose area. – Ed Beal Feb 19 '16 at 17:10
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This is probably just a sign of low quality construction, but nothing to worry about. A 2x10 over a 16' span will commonly have some cupping where it is bent slightly in one direction. With a long level, a slight difference between two boards may be magnified depending on how you hold the level, so I'd only be surprised by a 1/2" difference if that's between two other joists, rather than one of the ends of the level. You may also need to account for load from furniture above which may be deflecting some joists.

A better quality builder is going to do two things that will make this less visible. First, they'd use glue and screws. They take longer to install, but the result is no squeaking. Nails are faster to install, and that time is money for the builders. Second, the builder is going to check each of the joists for cupping before installing, avoid using the worst joists, and make sure all the cups are facing the same direction, up in the middle. They may even install wood blocking between the joists to transfer the load, which would reduce any difference in deflection from one joist to the next under load.

With your existing flooring, the screws you're looking at should help a lot. For future flooring, you'd need to look at the floor without carpeting to judge how level it is from above. You may be able to improve things with an extra layer of plywood with the joints offset. And if there are any extreme dips between two joists, you can sister a second joist on to the existing one at the correct height and screw the floor into that.

  • Some framers, if the plans explicitly call for screws instead of nails in the flooring, will use screws in nail guns to save time (nailgundepot.com/…). My personal take on that practice is that I don't like it. I figure if it's a screw, it should be screwed in, not blasted in on the assumption that the helix is going to turn and bite a little just because of the force of insertion. Any other thoughts? – Craig Feb 19 '16 at 15:37
  • Thank you for your detailed explanation. Regarding the sistering the joist, space in basement is such that I can't install 16 feet new joist, is it ok - if I sister with 3/4 plywood joist on both side of the offending joist, using 6 feet sections? – bob Feb 19 '16 at 16:14
  • The load is still carried by the existing joist with this design, so you can use shorter segments of 2x6 or 2x4. I prefer this over the option of shimming the existing joists because you can use a jack to get the correct height and you have continuous flat support for the subfloor rather than individual points of supports. I wouldn't use plywood on end for this since that doesn't have much structure laid on end and less of a target for screwing from above. – BMitch Feb 19 '16 at 16:37
  • Ok - so new sister joists stays bit higher than the original joists and provide support to floor above. Is it preferable to use screws to do sister joist or nails and what size? Thanks. – bob Feb 19 '16 at 17:00
  • Once you have the right height, I'd glue with construction adhesive and then lag bolt it into the adjacent joist. Clamp them together while working and predrill the holes. Get yourself some 3/8" x 2.5" long lags if not fatter, no need to go longer. An impact driver will be the perfect tool to drive them, and I'd space them one every 12" or less and 3" from each end. – BMitch Feb 19 '16 at 19:26
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Joists of varying height are only a concern if the floor (or ceiling) is wavy as a result. It's not a structural issue.

Screws are a good way to remedy the problem of squeaks and creaks. Be careful that they don't grab the carpet fibers and zip a row out. Run them in slowly, and open the fibers to expose the mesh before you start each one. It can also help to drive shims under the subfloor from below in cases where a particular joist is low. I'd use construction adhesive as well.

I generally agree with BMitch's answer, though around here we used 8d (nominal) ring-shank gun nails and construction adhesive for the subfloor. I've never seen one squeak. Where I am seeing squeaks in my current home is where the floor flexes under adjacent walls. the smooth nails holding the bottom plates down creak. I've had to run screws up from underneath to remedy some of that.

I'd use a self-leveler where you have noticeable undulation and want to install laminate. That stuff is generally fairly accommodating

Cupping is unavoidable. It happens after construction as well. It's not a concern.

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    Please don't put screws through the carpet, you'll kick yourself when you want to remove the carpet. They make special screws that drive through the carpet, and then the head snaps off. I've never used them, so I can't attest to their effectiveness. But I'm sure they make carpet removal much easier, as compared to using regular screws. – Tester101 Feb 19 '16 at 14:37
  • The screws run all the way to the subfloor if you do it right. They might grab a bit of pad, but it's not an issue if we're talking just a few. – isherwood Feb 19 '16 at 14:43
  • Thank you for your response. If I use self-leveler - Wouldn't the liquid in the leveler get absorbed by the sheathing and sag even more? I'm not 100% sure, but flooring is made up of layer of plywood and OSB below it. – bob Feb 19 '16 at 16:19
  • Self-leveling compounds are more like dough than liquid. When mixed properly they're like warm peanut butter, and they take a good length of time to settle. – isherwood Feb 19 '16 at 16:32
  • make sense. Can hardwood floor be installed on the floor as well (after using self-leveling compound)? Thanks. – bob Feb 19 '16 at 16:58

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