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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8 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?

  5. Sherry Says:
    January 1st, 2015 at 5:56 pm

    Hello. We’ve had a stack of particle board in the garage for 9-10 years (live in Houston and it was bought to board up windows during Rita Hurricane storm). I have a relative wanting to floor her attic for extra storage space in her home and asked if she could have it, I said yes if it’s useable.

    We keep our garage extremely clean, wash it out all the time and this pile of particle board has gotten wet over the years and where we live is either extremely humid in the hot months and damp in the cool/cold months. Is this something that should be given to someone? It looks fine, was never used, but it’s been in a humid and/or damp garage for almost a decade and I’m sure the strength/integrity of the boards aren’t what they should be even though I’m sure they were treated when they were new.

    If you can help or give any advice regarding this situation, I’d appreciate it.

    Happy New Year’s day, have a wonderful 2015, and best regards.

  6. RICHARD Says:
    February 14th, 2015 at 3:33 pm

    Take a piece of the particle board with you to the lumber yard. The dimensions of plywood and particle board have changed over the years and you want to make sure that you’re getting the right thickness. Being 1/16th of an inch off doesn’t seem like much, but it’s a lot when you’re dealing with floors.

  7. Trish Says:
    February 18th, 2015 at 7:45 pm

    There is a musty smell in parts of my house. It is carpeted. There are some bulges in the particle board flooring under the carpet. I wonder if the smell is coming from the floor? Has anyone else experienced a smell like this? It doesn’t smell like mould. The house has underfloor insulation installed six months ago.

  8. Nick Says:
    March 2nd, 2015 at 1:25 pm

    We recently bought a townhouse that was built in 1963 and was “remodeled” in 2012, some of which was new carpeting upstairs. Despite this, all three upstairs bedrooms were very loudly creaking. We were told by multiple parties (inspectors, appraisers, realtor) that it was 99% just loose joist nails that could be remedied with some strategically placed decking screws (yeah right).

    To make a long story short, we ripped up some of the carpet (which we were replacing anyways) and saw that the entire subfloor was composed of 3/4″ particle board (not just the top layer, the only layer). It was totally warped in a few places and had extensive water damage in others. I couldn’t believe that the people that had put $30k into the remodel didn’t replace these ridiculous subfloors when installing the (hideous) new carpets, but a massive tension headache and a few grand later we now have plywood in all the bedrooms.

    Just wanted this to be a PSA for people buying older homes with creaky floors. Yeah, it might be a few dollars to fix or it might be a few grand for new subfloors so that you don’t fall through a layer of particle board into your living room.

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