My installer glued down 1/2" solid pre-finished australian cypress flooring to a plywood subfloor using a urethane adhesive. The flooring is cupped. The installer has suggested sanding the floor flat and refinishing. Is this solution liable to be successful or should the flooring be torn out? What finish do you recommend for highest clarity, least coloration, and highest durability?

If a urathane adhisive was used then there is some outside moisture present. Was the subfloor within three points of the finished flooring? You need to find out if a moisture reading was taken prior to installation. Sanding the floor brfore the floor dries back out is a big mistake.

Sounds like a cheap waterbased adhesive was used, or no one had a moisture meter, to check the subfloor and the wood.

Sanding a cupped floor, becomes a crowned floor later.

Thanks Kevin. A moisture reading was taken, but I don't know the readings.
Thanks Floorguy. Are you saying that the only solution at this point is to tear out the floor?

Is this over a crawl space, concrete, or on the second floor of the home?

The house is on piers 9 ft above grade. There is fiberglass batting between the floor joists and the undersurface is enclosed with galvanized sheeting. I'm fairly certain the moisture content of the plywood subfloor was less than 12%.

What is the interior humidity, MC of the subfloor and joists, along with the flooring itself?


I bet money the joist and subfloor anre much higher in MC then the flooring is!!!

You may have the interior of your home too dry and not enough humidity.

Where do you live? Next to a river, ocean, lake, etc? If your subfloor is 9 feet above the ground, then the cupping is not from moisture in the ground. I suspect the flooring was not fully acclimated to your high humidity area and once installed, gained moisture and now appears "cupped". Some investigative work needs to take place to determine the reason for the floor to "cup". IF the subfloor was below 12% MC (you should get an actual #), that is the generally accepted MC range. But if your flooring was delivered at say 5 to 6% MC, the subfloor was at 11 to 12% and the RH was something like 70% and the installer didn't allow the floor to fully acclimate, you could have a cupped appearance. Moisture readings need to be taken of the subfloor (top and bottom), the wood flooring in different locations, the floor joists in different locations, etc. You may need an inspector.

Thanks guys.
I just got back from a meeting with the installer. The plywood subfloor had a moisture reading of 8% prior to installation. I don't know the reading of the wood prior to installation but the reading today is 5.7% which is down from the reading one week ago. The installer used acrylic urethane glue which contains water and is most definitely the culprit. The floor has laid down considerably in the last seven days. The exterior temperature has been running 80 to 90 degrees and I am running the AC with ceiling fans running.
My current plan is to wait for the moisture readings to stabilize, assess the appearance at that point, and if necessary sand and re-finish. Whaddayathink??

Open the windows and get as much humidity into the room as you can!!!

The interior of your home is too dry!!!

If the subfloor is 8% which is pretty nuch perfect, the the flooring 5.7, which is way too dry and suggest the humidity inside your home is around 25%.

Try to keep the interior ambient conditions between 65 and 80º with a humidity between 45 and 60%