My kitchen floor has developed a soft spot in front of the sink. While we have no water leak at this time a few years ago the dishwasher leaked a bit of water on the floor because of a bladder crack. I am not sure of what to do but was looking for some ideas.

I thought about going under the floor and placing a piece of plywood over the spot secured with liquid nails but I would appreciate any ideas or suggestions on how best to make a repair without having to replace the whole floor. Also, if my idea is a good one how do I prop or secure the plywood in place until the liquid nails dries.

Thank you in advance for any help provided.

  • Are you sure that the spot is from the leak from "a few years ago" or did you notice it then and are just now getting to it?
    – WarLoki
    Aug 30, 2015 at 11:43
  • Just noticed it. Wasn't there before.
    – tfrost2002
    Aug 30, 2015 at 12:24
  • 2
    If your leak was that long ago it maybe something new. Putting the plywood on maybe just a band-aid on a much bigger problem.You may need to find what is the root cause before it is to late.
    – WarLoki
    Aug 30, 2015 at 12:28
  • 1
    Unfortunately, as soon as a subfloor is compromised, there is little to do that is not just a time-bomb. If you support from below, it will still crumble, potentially hold mold, etc. Aug 30, 2015 at 17:55

3 Answers 3


It may be easier to repair the sub floor from below depending on the space available. From under the floor you would install the plywood repair piece so that it (if necessary) fit between two floor joists. Good idea when you mentioned applying construction adhesive to the new piece. As a final step have some lengths of 2 x pieces ready and fasten them to the floor joists so as to support the newly installed plywood patch. There is a chance for the joists to be made of steel in which case carriage bolts would be substituted for wood fasteners (and pilot holes drilled in the steel).

  • I have the space as the home is on a block foundation. I will check this out and see. Thank you for your help.
    – tfrost2002
    Sep 10, 2015 at 7:35
  • Your welcome. I hope you found the information provided for your answer helpful. If so, as per Stack Exchanges instructions to all new members.."Voting is central to our model of providing quality questions and answers..". So it would help others whom might have a similar question if you voted for any answer you found helpful.
    – ojait
    Oct 13, 2015 at 18:06

I mostly agree with ojait. But, I'd nix the plywood on the joist cleats. Plywood's great & all but it ain't stiff like wood. Oak shelving or stair tread as your backer, with or without glue, can't be beat...grain perpendicular to the joists.


Old post but I thought I’d add for new readers. There’s a product at Home Depot that will harden dry rotted wood and prevent mold. I think it’s called Rotted wood Restorer by Bondo. I wouldn’t recommend on huge areas or support beams but may do the job for a smaller area.

  • 2
    "Wood hardener" is the generic name. It restores some bearing strength. You would likely still need to undergird the bad spot. If the wood has taken on a cork-like compressibility, however, then the hardener would work to mitigate some of that compressibility.
    – popham
    Mar 19 at 6:23
  • Agreed. Wood hardener is more appropriate for small areas, and even then you usually need to first remove the worst-damaged material and fill in the space later with something else like a epoxy filler. More useful for surface trim than for anything structural.
    – keshlam
    Mar 19 at 14:39

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