Flaking polyurethane finish

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Q: We recently refinished the 1700 sq ft of red oak wood floors in our home. It had been a prefinished floor when initially installed, so it was a bear to sand down, but we got it done. We sanded them well, vacuumed and wiped them before applying stain. We stained with oil based stain then put on 4 coats of oil based varathane polyurethane. Now, just weeks later the floors are flaking in small areas and in between boards. How can we fix this? Thanks!

A: Question: given that this was factory finished, did you sand it down until the bevels disappeared? Or, if they were large bevels, did you hand scrape the existing finish off each one? If not, that could account for the flaking finish. Adhesion issues generally fall into two categories: contamination issues and insufficient inter-coat abrasion. In other words, if the previous finish application is not thoroughly abraded with a fine abrasive you may fail to gain good adhesion. You are likely going to have to start the entire process over because you likely can’t know at what stage the adhesion issue begins: between the 2nd and third coats? Maybe between every coat? If you attempted to screen most of the finish off it would be near impossible not to disturb the stain. 4 coats sounds like a bit of over kill also. By piling on too many coats at once, you impede the time for the previous coats to cure. If I used a stain containing urethane resin such as Dura Seal quick coat, I would stain and apply 2 coats of poly. Other stains I would apply 3 coats.

Follow-up Q: Yes, we sanded down beyond the bevelled edge, so the floor was completely even. We sanded with 20 grit, 40, 60, 80, then 100. We followed the directions on the varathane can, which stated we needed 3 coats at minimum, but more was preferred. The thought of starting over makes me sick, but if that’s what needs to be done, so be it. Is there a better finish we should be using? We have many scratches already (though we knew some would be inevitable, as we have a large Labrador). Thoughts on tongue oil? Thank you for your advice.

A: For a polyurethane finish I’ve never used one better than Poloplaz Primero. It’s tough and easy to work with. Waterlox is a nice tung oil finish, though somewhat expensive. While not offering the hardness of a polyurethane it is very easy to refresh it.

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