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

debndulcyJune 1, 2011

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.

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brickeyee

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.

    Bookmark   June 2, 2011 at 12:28PM
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HandyMac

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.

    Bookmark   June 2, 2011 at 12:46PM
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debndulcy

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.

    Bookmark   June 5, 2011 at 2:10PM
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