What causes cupping?

salpek · **Joined:** Tue Jun 13, 2006 5:33 pm **Posts:** 3

Hi there, I have jatoba installed, 5 inch board, prefinsihed and it is cupping (I am hoping thats the right term, from reading other msg it sounds like what I am seeing. Boards bending up along the sides). I have been reading lots of posts and am a bit confused. Its it too much humity or not enough that causes it? I live in a fairly humid area, but have something that takes the humidty out of the air in our house. AND is there anything I can do to correct this or make it look somewhat better. I have over 2000 sq feet of it :-(

Thanks for any help you can give.

ChuckCoffer · **Joined:** Fri Aug 06, 2004 6:19 am **Posts:** 703

Cupping is the result of a moisture imbalance in the wood.(So is crowning)

Your wood is higher in moisture on the bottomside than it is on the top. Moisture content equals dimensional change.(more water=bigger wood; less water =smaller wood.)

I would bet a dollar that your problem is a result of moisture migration from a subfloor that was too moist. The same phenom can be caused by the environment being too dry, but that is extremely rare.

Floorguy · **Posted:** Tue Jun 13, 2006 11:27 pm

Yep, the bottom of the board has more moisture content, then the top of the board.

Meaning it is installed over a subfloor that has a high moisture content, from either fast paced building practices(New construction homes) Or your crawl space/ basement is very humid.

Or

After the installation was complete, you cranked up the dehumidifier, instead of having it running before acclimation, right on through the completed installation and until now. Maintaining the ambient conditions close to what it was when it was acclimated and installed at.

salpek · **Joined:** Tue Jun 13, 2006 5:33 pm **Posts:** 3

Thanks for the info. But now that is has happened is there anything I can to fix it or make it look better.

KevinD · **Posted:** Wed Jun 14, 2006 2:59 pm

Cupping is a jobsite related problem so you first need to indetify where the moisture is coming from. Is the floor over a crawl space, concrete, finished basement?

salpek · **Joined:** Tue Jun 13, 2006 5:33 pm **Posts:** 3

It is installed on the mail floor over a 8ft unfinsihed basement. If we figure out were the moisture is coming from and controll/fix it, will the floor go back to normal? Thanx in advance.

Floorguy · **Posted:** Wed Jun 14, 2006 7:14 pm

Put dehumidifiers and fans in the basement!!!!

It might go down in a couple of months, once you pull the moisture out of the subfloor and joist from below.

You need to invest in a hygrometer to read temp and humidity, for both your interior and the basement. Keep them about the same levels, and you won't have cupping.

What causes cupping?

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