We bought this house, it was almost all carpet except the kitchen and bathroom which were sheet vinyl. The house smelled musty and the carpet was OLD. It has all been torn out now.
I've read dozens of articles, forum posts, and blog posts and I'm concerned.
There are many "particle board is trash" or "it's worthless" posts and while I can appreciate that point it doesn't help me. The house is over 40 years old and the floor hasn't rotted out, so obviously something is working. But since carpet is not a vapor barrier there are plenty of stains and swells throughout the house I don't want to leave things as they are. Northern California is not an excessively humid environment but we do get a fair amount of rain during winter and spring so obviously this floor has seen a lot of moisture.
Our hope was to replace the carpet in some of the rooms and do a water proof vinyl floating floor in others. But looking at the water stains and the uneven nature of the floor I didn't really like the idea of just putting flooring down on the subfloor without some sort of future proofing. My contractor is currently planning on installing 1/4 ply over the whole of the floor in preparation for the aforementioned flooring.
One article I read said that sealing the particleboard would accelerate the deterioration since any moisture from below would no longer be able to evaporate into the living space.
So is there a question in all this?
I don't like the floor as it is now, it's noisy, uneven, and slightly stinky. But I don't want to seal it, cover it, or level it if that will cause it to fail faster.
Tearing out the whole sub floor of the house and sistering on new joists to hold new flooring is not an option.
Right finally the question.
Should I just let my contractor do his thing?
Should I ask him to seal it first?
Several manufacturers require OSB or Plywood for their flooring, fortunately those were all hardwoods or laminates which I won't be using. A number of places indicated that particle board subfloor was only suitable for carpet and floating floors. But other sites indicate that any floating floor gets its strength from the subfloor which in my case is not the most ideal of surfaces.Livingroomfloor

  • As long as the particle-board isn't deteriorating (the glue bonding the particles together failing), then there isn't any need to replace it. The vapor-barrier is usually provided on the underside with "Kraft Faced" insulation used between the floor joists (and potentially an additional plastic barrier). The concern with putting laminate or wood floors on top of particle board is particle board doesn't have much tensile strength (nails into it can simply pull the area of particles holding the nail out). Sealing with a cheap polyurethane is an option and it will help with the musty smell. May 5, 2022 at 1:38
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    "Tearing out the whole sub floor of the house and sistering on new joists to hold new flooring is not an option." Why tear out the subfloor and sister new joists? If the joists are failing/improperly sized, they'll need to be sistered or replaced anyway. If they're not, there shouldn't be any reason to replace them when replacing the subfloor. 1/4" plywood won't fix a wavy floor, it's thin enough it'll just conform to the dips. Maybe not on initial installation but give it a winter and it'll match what you've got now.
    – FreeMan
    May 5, 2022 at 11:31
  • Particle-board and water do not mix nicely. If it kept dry it will last, but if it gets wet then it is a remove and replace job for that section/s. Mention swells in the the question, swells will need removing, typo for smells is different.
    – crip659
    May 5, 2022 at 15:01
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    My comment about new joists would be my poor way of addressing the need to make sure there are joists to mount to since the walls sit on top of the sub floor. Any new floor would require something onto which it could mount and if the joists are under the wall I would need something new. May 5, 2022 at 15:18
  • Would recommend replacing any particleboard found in bathrooms or other areas subject to water exposure. There is no sealing method in the world that will prevent wetting of bathroom flooring. Such wetting of particle board will result in unfixable swelling and eventually turning into something resembling peat moss.
    – kreemoweet
    Dec 26, 2023 at 11:57

2 Answers 2


If you're not going to remove the particle board I would suggest grinding the humps and swelling down. Any soft spots should be removed and repaired.

Seal with Zinsser Odor Block or something similar and then glue and screw (or use ringshank nails) your 1/4 plywood down. This should eliminate some of the squeaking and the smell.

Installing new flooring over this shouldn't be an issue.

  • Thanks that makes sense. The plan is to use screws to hold down the new plywood because of the difficulty getting old particle-board to hold nails. Also it should help with squeaking. May 5, 2022 at 15:20

5/8" or 3/4" Particle board is typically installed ON TOP of 1/2" minimum plywood sheathing. No one should ever be putting particle board over joist. That is sh*t construction. The plywood is fastened to the joists and the particle board is fastened down to the plywood/joists. If you have squeaking floors, it's usually the plywood that is not firmly fastened to the joists, or the nails have backed off/become loose. Not everyone installs flooring using good fasteners. Most just use what is cheapest. You want something to stay tight? Use ring shank nails or screws. When I pull carpet, if there's any doubt about the flooring, it gets replaced too. The plywood gets new fasteners and the new particle board gets countersunk screws on a 12" grid. If I were installing real hardwood floors (not laminates), I would pull up the particle board subfloor and install 3/4 or better plywood. Having a layer of 1/4" plywood on top of poor condition 3/4" particle board, which is on top of 1/2 plywood sounds like installing hardwood floors on top of a sh*t sandwich, and is likely to be a future of problems..

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