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sanding marks in a fresh hardwood floor

toler's picture

Drum sander marks in a freshly laid/finished 3/4 oak floor. I gave the sub a chance to resand and finish but highly visable sanding marks remain. The installer is now claiming that deflection in the sub floor and joist is causing his machine to bounce and that the problem is mine.
The floor is built as follows. 2x10 joists 16" on center, 11' span, x brasing, 3/4" cdx T&G sub floor. As far as I'm concerned If there is any
bounce in the floor, and there isn't, it's besides the point. He accepted the sub floor as adequate when he put down the firs plank.

Any one know what is causing the sanding marks?

I gave him a chance to fix the problem and he failed, should I tell him to take a hike?

(post #68545, reply #1 of 8)

Sounds like he may not be going up to a 80 grit but doubt any floor guy is that stupid. Or his machine is F'd. If there was bounce you wouldn't get scratches, you'd get chatter marks. I'd tell him to walk. Sounds real basic unless there's something I don't know.

Be floored?


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(post #68545, reply #4 of 8)

chatter marks? I wouldn't call them that per say. they are not patterned that way. They are also not what i would call scratches more like drum divets from stopping and pulling back. Could this be my fault even if there is bounce in the floor? I mean I wouldn't set tile over a floor with movment and then tell the costomer the reason ther grout is falling out is do to a bad sub floor and thats there problem. right?

(post #68545, reply #5 of 8)

Sounds like he does not know how to sand a floor.  Sanding marks will be marks such as lines left by the granuales that are on the paper itself.  These are easily taken care of by going progressivly to a finer grit.  The last floor I did, which was by own, I went down to 180 grit and finished it out with a 6 " palm sander and 220 grit.  Lot of work but the finish was excellent.  The fact he is saying that the sub floor is bad is a "pass the buck" syndrome.  No floor with the spec. you gave is going to bounce and cause ripples in the floor from a floor sander.  I would tell him to fix it or get lost and maybe a 6 pak of beer for his trouble. 

(post #68545, reply #2 of 8)

Rookie on the sander. It happens. It's his bust. Completely. The business you hired needs to fix it. You shouldn't have any sanding marks visible at all.

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(post #68545, reply #3 of 8)

Tell the idjit to go buy himself an R.O. floor sander if he can't run a drum. Cripes, Aunt Mazie could do a perfect job with one of those....



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foolish men call Justice....

(post #68545, reply #6 of 8)

Loose nut behind the wheel ...I did a fir floor for the first time in my life at 26 years years old, did the same as what you describe..dropped the drum too radically and didn't feather out the divots.

I saw it before finish and belt sanded the hickies out....arrgh.

You got a newbie I suspect.  Sounds TOO familiar.

BTW, that floor was just 3/4 t&g over 20" spaced 3x10's spannig about 11' , exposed on the underside. No "bounce", just my operater error.

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(post #68545, reply #7 of 8)

Clearly operator error.  With a reputable floor installer we still get an inexperienced guy who leaves divots and we call them back to fix the problem.  After the first call back we'll fix it ourselves and back bill them.  Hopefully you have a little financial leverage and they'll fix it for the final payment.


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(post #68545, reply #8 of 8)

Sounds like what we call 'stop marks', they're from when the big sander stops moving forward and momentarily stops and starts moving backward. Anybody worth hiring knows this and will feather out the drum as they approach wall and raise it off floor as they stop. Then as we backup, we slowly relower the drum. If they didn't do this, they shouldn't be for hire. And if they refuse to fix it, they shouldn't get paid.

A second possible cause would be if they used a drum sander and the drum is not adjusted perfectly. This acn cause the machine to set up 'dynamic harmonies' (for lack of a better term) where the machine is vibrating and the right tone matches the floor and you can get waves but they will only happen in certain spots across a floor. If they are consistantly about a foot off the wall, this is 'stop marks'!