Patching old polyurethane floor with new polyurethane

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gzt

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#322818 24-Sep-2025 15:11

Old polyurethane floor worn through to the particle board in high traffic pathways. It is a source of dust so something needs to be done to seal it.

I'm not terribly keen on sanding because more dust. Is there any alternative method to prepare old polyurethane for a new coat? The finish does not need to be anywhere near perfect and won't be. The aim is to seal it. It will likely be covered with carpet after sorting out this issue. I don't want it to continue to generate dust or flakes underneath a covering.

If not I guess I'll hire an appropriate sander and an oversized dust extractor.

richms

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#3418543 24-Sep-2025 17:07

Poly will not bond to itself once fully cured, it needs mechanical keying. If you do not sand you will get a nice shiny layer that just peels up like a sticker once the bond breaks with the old stuff. There will also be a crapload of household cleaners sitting on it like pledge and floorwax and also things like embedded skin grease from people shedding that will prevent adhesion.

I am not aware of a solvent that will make it go tacky again to accept another coat like you can get for some paints and plastics as adhesion promoters, I would just clear the room out, block the gap under doors and go for it with sanding. Have had to do this twice in my loft now when I made the mistake of using some water borne crap garage floor paint instead of the prior solvent polyurathane based stuff that I used in the past as it did not adheire well even with the sanding I did. The cleanup is not that bad in an empty room, just clean it off the tops of skirting and windowsills incase it gets blown into the wet poly. I was not using transparent poly, which thankfully hides all the sins.

Richard rich.ms

mdf

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#3418550 24-Sep-2025 17:48

If it is flaking, you can probably get it up with a linbide scraper (so flakes rather than dust). That might be okay for a small area but for anything large will be more effort than a floor sander and dust extractor. You'd also need to be a little careful not to gouge particle board since it will be obvious under the polyurethane.