hardwood floor finish

I have an oak floor that was installed in 1962, and carpeted over sometime later, probably in the mid 70's. It appears to be in pretty good shape under the carpet, aside from holes from staples and tack strips. I would like to fill in the holes and apply an oil based polyurethane.
Can this be done without sanding to bare wood? I have no idea what the finish on the floor is, maybe varnish, maybe wax, maybe shellac. How can I tell for sure? And if it is shellac, with poly stick to it? I know if its wax the wax has to go, but can it be simply stripped off with ammonia or will it require sanding to bare wood?
If a complete sanding is necessary then either the carpet will stay or I will live with the holes left in the floor! I've done a total sand/refinish once, I'm not going through that again! I have another room that needs the carpet removed and floor refinished but that one definitely needs the full sanding so maybe I will have both done professionally at some point in the future.
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Yes. If you are satisfied with the appearance, no need to sand all the way down.
I have no idea what the finish

Shellac was the most popular finish years ago, but urethanes have long since replaced it. Put some alcohol on it. If shellac, it will soften and dissolve. Shellac is also a good barrier between coats of incompatable materials so yes, poly can go right over it.

I would think it could be stripped but I've never done it myself. . Do a test in a corner where it will not be seen.
--
Ed
http://pages.cthome.net/edhome /



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We just had our floors redone last week; sanded multiple times, stained twice and polyurethaned three times. I was kind of put off by the fact that they didn't fill the holes left by tons of carpet stapes, tack strips, etc. But they said they would just come out, as it's 100 year old wood. (???) But, we got a great deal at $1.75/sq. ft. and it will be the most cosmetically improving repair we'll do; and they were done in three days. Wow...it was so nice to just walk in and have all of that done!
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wrote:

Wow, for $1.75/sq ft I would have the guy there right now. I was quoted $4 for sanding to bare wood and 2 coats of poly. Seemed like a rip off. It seemed obvious to me that the guy was high-balling me, he seems to have more work than he can handle and told me it would be 6 a month minimum wait if I wanted the work done.
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wrote:

Assuming it is a urethane I would think I could lightly sand it to scuff it and go over it with a coat of poly, correct? Would water based Varathane work okay? It dries so much faster and doesn't stink. Same question if it is shallac, can water based go over it? I suppose once I determine for sure what the heck the finish is I can probably call Varathane and ask them what they recommend I use.
Thanks
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As Ed pointed out alcohol will soften/remelt shellac and as for waterbased Varathane as topcoat it has to be DEWAXED shellac. Zinsser recently introduced Seal Coat, a dewaxed shellac in a can with a shelf life of three years! I mix fresh dewaxed shellac and it has typical shelf life of six months. Many prefer avoiding the odor and longer dry time problems of oil based finishes by using water based.
J Kelly wrote:

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