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hardwood floor sanding w/diff't grits- affect finishing?

Posted by debndulcy (My Page) on
Wed, Jun 1, 11 at 20:21

Hi, (I figured woodworkers probably easily know the answer to this, though it's about wood flooring.)

I'm in the process of sanding my oak hardwood floors with a rental sander, using 100 grit. They were totally re-done/taken down about 10 yrs ago, so I'm trying to get out scratches and get a clean, new poly finish. Some scratches are deeper and I've been using my hand sander w/80 grit trying to get them out.

The poly previously applied was pretty worn out in a lot of places and wood not sealed, (I've worked on the place a lot unfortunately AFTER the floors were done) - so altogether
I'm concerned now about what it will look like with the first coat of polyurethane on it. Does the underlying finish need to be totally uniform - to have a uniform looking finish? Is there a sealer or conditioning product I should use that might insure that?

THANK YOU very much for your input and advice.


Follow-Up Postings:

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RE: hardwood floor sanding w/diff't grits- affect finishing?

Any variation in the wood surface (even the scratch pattern let by different sanding grits) can affect the appearance of the finished floor.

A final sanding pass should be made over the entire floor to get an even finish.

I had a guy once who had a helper apply the finish to half a large room.
Sure enough, they had enough difference in technique applying the finish that the floor looked different on each half.

Time for another coat.


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RE: hardwood floor sanding w/diff't grits- affect finishing?

When I installed the unfinished flooring in our house, I started with 80 grit. Then 100 grit and finished with 150 grit. That was using a sander called a U-Sand. It has four large rotary sanding discs much like random orbit sanders.

The flooring I installed is hard maple and I used only oil based floor poly as the finish, no coloring. And it is gloss.

The reason I finished with 150 grit is because I am a wood worker and 150 grit is generally the last step for obtaining a good finish on any wood. That grit as the final step allows colorant(stains/dyes) to be absorbed by the wood well and still eliminate scratches.

Three coats of most finishes is the recommended amount. That helps the final look and protection.


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RE: hardwood floor sanding w/diff't grits- affect finishing?

Thank you, all. Was having computer problems and thus not able to see my question (re duplicate above) or any responses, until now.

After reading and inquiring more, I stayed with the sanding at 100 grit (and am applying 2 coats of poly). I was trying to get the same effect as w/screening. My understanding is that the 2 coats will sufficiently cover any small spots/areas where I went down to the wood to get deeper scratches out. It's also all I'm able to invest at this time.

Reading the can of Minwax's fast-drying poly, it says it levels well and isn't as (extremely) sensitive to stirring/not stirring (though of course I'll be doing it regularly). I believe with different people (responding to brickeye's comment) working on the same large floor, the topcoat probably matters most, - and consistent stirring for a consistent finish.

What a job! 'Wish I could have had pros do it, but doing it myself, am very grateful for input of forums like this. Thanks again.


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