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Home » Troubleshooting/Inspections » Cupping

For problem floors and inspection-related issues.
8/10/2011 9:19:38 AM

Steve Garner
Steve Garner
Posts: 5
This is a Sand and Finish Job. The home is approximately 12 years old. Hardwood throughout most of the house. New home owners wanted the main areas of the house resanded and finished. (Halls, Foyer, Kitchen, living area) Sanded at put down a quick dry sealer and 2 coats of oil poly. Now the areas we sanded and finished are cupping and the part of the house we did not sand and finish have stayed flat. No new wood, all existing. What could cause this to happen?
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8/10/2011 11:11:32 AM

Roy Reichow
Roy Reichow
Moderator
Posts: 355
What was the previous floor finish?

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Roy Reichow
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8/10/2011 11:36:01 AM

David Harrison
David Harrison
Moderator
Posts: 437
What did the floor you sanded and finished look like before you sanded it?.....why did they only want part of it sanded and finished?
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8/11/2011 8:08:58 PM

Joe Clarke
Joe Clarke
Posts: 27
Steve, One needs to know more about the previous floor finish and condition of the gaps and so forth to be of real help. Keep in mind that cupping is always moisture related. The new finish is likely sealing the floor surface more than the previous finish, and the bottom of the boards are now "loading". If enough information were available, a prediction may could be made that the cupping issue will self correct in a few weeks.
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8/15/2011 11:49:12 AM

johannes
johannes
Posts: 410
Steve,

I'm guessing that the remaining old floor/finish has been buffed and coated before once or twice.

When a floor gets sanded and refinished (thin seal and 2 coats in your case) there likely may be less finish on the refinished floor compared to the old one. With a thinner layer of finish the flooring may loose some moisture thru the thinner film and the result is some surface cupping as the floor shrinks a bit on the substrate.

Did you notice anything happening during the refinishing of the floor? between coats when buffing, did you notice edges being abtaded thru if they started to lift slightly (that's what would happen if the flooring is cupping after being sanded).

What is below the floors, a basement? Is there a dehumidifier running in the basement? Has anything changed in the basement, it sounds like the floor over the basement is afefcted and not the rest. Is the rest upstairs?

Only thing you can do is wait untill the winter and inspect the floor (along with the floor that was not sanded if that floor is also over the basement) sometime around February to see what the floor is doing. You need to know what the sanded/refinished floor does compared to the old floor and vice-versa.
If you sand/refinish now it will likely develop a crown in the winter. If you see movement that is opposite to what it is doing now you may only be able to correct it by sanding/refinishing it inbetween both variables. That would be somwhere between the end of the winter and July to allow the floor to reach a point inbetween.

As Joe is suggesting; variation in MC does this stuff.

Johannes.
edited by johannes on 8/15/2011
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8/15/2011 3:39:58 PM

sammy
sammy
Posts: 1
If part of the floor has been water damaged before and it's been sanded, and the other part wasnt water damaged are sanded and now you sand all the floor the part of the floor that allready had been damaged wont cup after sanding unless it gets a lot of moisture it usually will expand and after drying youll see gaps between the boards.
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8/15/2011 4:51:46 PM

Rick
Rick
Posts: 1
You say new homeowners? This may be a stretch, but if there is a basement/cellar, any chance they had a door to the cellar open for extended periods during the move? During muggy summer days, that may have introduced a whole lot of moisture into the cellar.
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