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In my bedroom, the plywood subfloor has a depressed region near the middle (roughly (roughly 10ft x 10ft). The depression is about 1/2 inch on average, and up to 3/4 in a small area. I want to put down laminate flooring, but am not sure what's the best way to level the depression. I read about leveling compound, but read it may be cheaper to patch with plywood pieces. Could I use 1/4" thick plywood pieces for this? If so, are there additional steps besides nailing it down?

Forgot to mention, this is a second floor condo unit.

  • Do you know what has caused the depression in the first place? For example, if you have joists below the floor that are sagging, I'd worry about whatever structural issue caused the joists to sag before I put the additional weight of leveling compound on top of it. – Eric Lippert Sep 16 '16 at 22:27
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    Wow a 1/2" over a 10x10 area that is a lot of leveling. I would fill the center with underlayment and level to the edges . But what caused the drop is the more important question. – Ed Beal Sep 16 '16 at 22:47
  • I don't know what's causing the sag. This is a second floor condo built in 1967. I suspect it was just poor construction. – user7014 Sep 16 '16 at 22:50
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First you need to address and fix the sagging issues before proceeding with any thoughts of next steps. Get under the house and see what's going on. If it is not severe (ie. rot/mold) then get proper bracing in there.

After that, you should most certainly be dealing with a much more level floor. As for liquid level vs. replacing the subfloor. It is much more cost effective and ideal in laying fresh particle board on top and have a nice new surface to start with. Liquid level will work well when no more than 1/4".

Could I use 1/4" thick plywood pieces for this? If so, are there additional steps besides nailing it down?

I would go with at least 3/8" particle board and as for nails, DO NOT USE any. Screw it all down, or the nails can get loose over time and make the floors squeak.

With that, make sure to screw off all areas that squeak, or you will live to regret it.

Update Based on it is now a Second Floor Condo. Are both floors your condo and do you know much about history?

I apologize if this type of reply is not allowed. As I will remove this portion or answer in full depending on info to come.

  • I do appreciate all your help. I do not own the first floor. I don't know much about condo history, but I do know from other condo owners that this seems to be a common problem in the nearby complexes. – user7014 Sep 17 '16 at 15:16

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