Home Improvement Expert Danny Lipford

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How to Remove and Replace Rotten Particle Board Subflooring

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When replacing the flooring in our house, we found rotten spots and bubbles in the particle board subfloor. How do we repair the damage before the new flooring goes down? -Lisa

Hi Lisa,

Particle board is easily damaged by moisture and water, making it a poor choice for subflooring. Unfortunately, that hasn’t stopped it from being used. The only way to repair deteriorated or rotten particle board subflooring is to remove the damaged areas. Here’s how to go about it.

To remove damaged sections of particle board subflooring:

  1. Safety: Wear an approved respirator or dust mask, safety glasses, and earphones or earplugs before cutting into a particle board subfloor; and close or cover doorways and HVAC ducts to contain dust. Particle board is often made with formaldehyde glue, and cutting it generates a lot of fine dust, so it’s important to protect your lungs. Safety glasses are important, too, since you may hit unseen nails while cutting through the subfloor.
  2. Locate Floor Joists: Determine the location of the floor joists using a stud finder or by the seams in the existing subfloor.
  3. Mark for Cutting: Use a chalk line to mark the area to be removed, making sure the end cuts are centered over floor joists.
  4. Cut Damaged Subfloor: Set a circular saw to the proper depth, so it cuts just through the thickness of the particle board, and make the cuts.
  5. Remove Damaged Subfloor: Use a flat pry bar to remove the damaged particle board. Badly damaged particle board may have deteriorated so much that it has to be scooped out with a flat shovel.
  6. Remove Nails: Pull out any remaining nails in the area where the particle board has been removed.
  7. Cut New Subfloor: Mark a piece of plywood, that’s the same thickness as the particle board, to the correct size using a chalk line or straight edge; then cut it to size.
  8. Attach New Subfloor: Attach the new plywood subflooring to the floor joists with construction adhesive and screws.

If your time and budget allow, I would remove all the particle board subflooring and replace it with plywood. But if you feel the undamaged particle board will remain in good condition, you would only have to tear out the areas that need replacing.

If you’re installing tile, put a layer of cement backer board on top of the subfloor, or use a waterproof underlayment membrane, so the tile will adhere properly.

Good luck with your project,

Danny

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4 Comments on “How to Remove and Replace Rotten Particle Board Subflooring”

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  1. Michelle Mitcham Says:
    April 30th, 2012 at 2:43 pm

    Thanks Danny–this was an excellent article, and just the kind of information I was looking for. I bought a late 50′s house that had a large room addition along one whole end of the house. Unfortunately, they cheaply used particle board for the addition. Of course, between dogs and grandkids, I have several ‘humps’ in the floor under the carpet. I will look for you about my squeaky old solid oak flooring in the rest of the house too.
    Excellent advice–Thanks again!

  2. Patrick M. Says:
    May 4th, 2013 at 2:19 am

    Hi,
    We have particle sub-flooring in our home that was not properly installed to prevent moisture damage. As a result 10 years later, we have rotten spots and warped spots all over the house and is delaying installing vinyl hardwood like plank flooring.
    Because our budget will not permit replacing the entire sub-flooring in the house and installing beautiful vinyl flooring that looks like hardwood, is there an effective and cheaper way to replace the rotten spots seal the warped spots and prevent the rest of the subflooring from moisture damage so that we can install our flooring. Please HELLLPPP!!!!

    Sincerely,
    Patrick M.

  3. Bart Says:
    July 25th, 2013 at 7:10 pm

    Patrick.. Particle board is like a sponge to any moisture. I’ve got the same problem.. slowly replacing each room.. 1 room at a time, but also working on the vapor barrier system under the house. “under house ventilation and moisture barrier” -that’s the dirty work. The only way to really fix it.. tear up the old flooring and replace it with Good Wood. I don’t recommend throwing ply on top of it. Under your house you should also have a Vapor barrier to protect the sub-flooring from moisture which rises from the ground up, incorporated with flooring insulation system. If not.. that will slowly destroy any sub-flooring system.
    -Bart

  4. Evelyn Bobo Says:
    January 2nd, 2014 at 10:44 am

    Is there anything special we should do to replace the bathroom floor that is rotten? Do you consider this a DIY project or should we hire a contractor?

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