Second coat of polyurethane not drying

Q: We are having wood floors installed in a relatively new house (10 years old) on the upstairs bedroom floors. We are using a well regarded installation company. They put the floor down in one day, stained the second day and put the first and second coats of polyurethane on the third and fourth days. They have buffed in between all coats and expected to sand and put the final coal of polyurethane on the fifth day, but the second coat just is not drying.

It has now been drying for nine days and is still tacky.

They can’t explain it, but have suggested that there might be a humidity imbalance in the house. The humidity in the upstairs has been about 55% and the temperature in the house has been maintained at 72 and there is plenty of air circulation. It has now gotten a little colder and the heat is on in the house, with humidity at about 55% and the floors still are tacky. This area has had non-stop rain virtually for six weeks, but they say they are having this problem only in my house. They also are telling me they’ve never had this problem of polyurethane not drying before.

I’m wondering whether it’s possible they put the second coat on too fast after the first coat and trapped moisture in there or whether they put the second coat on too thick. Are there other explanations that could cause this problem? Could it be a humidity problem?

A: Coating can be tricky at times. It sounds like you have a decent environment for coating. However, constant rain and no ventilation in the room can present an issue, though 9 days and still tacky is a tough one to explain, especially with the heat on. If this room is above a cold zone, such as a garage for example, you might actually have a cold floor (cold air hitting the sub floor of the bedroom) or the batch of finish they used is seriously old and the dryers are not working in the finish anymore.

Follow-up Q: The rooms are above the main level of the house which is above a walk out basement, and not above a garage or cold area. I’m at a loss as to what to do. Heat has been on for three days and the floors are still sticky in areas. Will they need to re sand and start over?

A: If the first coat was not dry they likely (though not guaranteed) would have known as soon as they tried to buff it. Additionally if the first coat, or any coat was not dry before applying another coat, the finish will wrinkle, like alligator skin. None of that happened, so we should be able to assume the first coat was dry. The second coat will not dry. It’s been 9 days. This is new wood. You have the heat on. I would suspect the finish if I was them and I would have been on the phone to the manufacturer of the coatings they used after day one to find out what is going on. 9 days? The only time I’ve seen something like that happen was in the mid seventies in Toronto when finishing very old floors that had been waxed for years. You can’t get the wax from between the boards and the solvents soften it and it repels the finish, usually along board edges and it takes weeks to harden. But that is not the case with your floor. They may very well have to sand again. I think I would try wiping the floor down with mineral spirits or alcohol first to see if you can force it to dry. Ventilate the rooms well and maintain heat.

I’d be curious to know how this turns out.