Uneven subfloor


Old 07-14-09, 07:33 PM
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Uneven subfloor

I'm installing hardwood floors for the first time so I'm unsure what to do in this situation. My subfloor seems to be uneven and if I press down on one end of the hardwood board, the other end doesn't touch the subfloor. Some ideas I had was to shave down the higher subfloor until it's even with the lower or apply several layers of tar paper until it's even. What is the best way? See the pictures of what I'm talking about below.

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Old 07-16-09, 07:57 AM
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A couple of solutions

Hi btbowden,

An uneven subfloor is indeed a frustrating problem. However, there are a number of ways to can tackle this problem.

Firstly, you can buy self-leveling compound that can be laid on the uneven parts of the floor. This is like quick drying concrete that you see in posts and can be applied just to the parts that you want to level.

It's best to add small layers and then check with a spirit level. You can then lay the floor directly on top of the leveling compound. This method is much simpler than screeding, which is where you add concrete to the whole floor to level it.

Self-Leveling Wood Flooring Compound

The second way of leveling is to add battens, soft wood that you lay over the whole floor. Since the battens stretch the length of the wood floor, this should level out when you put the wood flooring over the top.

Check out some battens over at Real Oak Floors: Wood Flooring Battens

Hope this helps!

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Old 07-16-09, 08:46 AM
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Looking at the photos, it appears you are installing a solid floor, to be stapled or nailed. In that case, self-leveler,concrete, screeding the floor are all bad ideas...they are not suitable for mechanical fastening, only for glue down or floating installations. You definitely would want to grind/sand any high spots, then level the low areas with tar paper.
Old 07-16-09, 01:39 PM
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3/8"?? I'd also be looking at support from underneath to see if the subflooring is actually sitting on something solid. I can't imagine it being off that much without a structural boo boo. Gotta fix the fault first.
Old 07-24-09, 08:53 PM
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floor leveling

take a 6'- 8' straight edge and go over the floor with it( perpindicilar/ right angles to the joists). that will show any low/and or high spots. your subfloor is osb board and i would definity sand/grind the seams as this subfloor seems to swell more at the seams. we use 30 lb roofing felt and shingles to level with, and we never go over 2 layers of shingles. some rolls in the floor will be there and you may just have to live with them.
it looks as though you will be butting into an existing floor so you have to keep it the same height at that point. not a lot of flooring companies bother to level, so i would imagine your other floors have rolls in them.
when installing i would put down 15 lb roofing felt and mark the floor joist ,( i use sidewalk chalk) so you can nail into them,as this makes a stronger floor.and helps with squeaks down the road. if you are using a floor machine put tape on bottom plate as this helps prevent scratching when installing floor. keep some of the box behind you to put your equipment on as you are installing the floor, and as a path to where you are cutting to keep as much dust off floor as possible
good luck and take your time

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