When Sanding Goes Wrong on Engineered Floors
Every so often, a job comes along that keeps you on your toes, the kind where experience really counts. This particular floor was one of them.
From the moment I lifted the threshold and spotted the tell-tale plywood edges, I knew we were working on engineered oak, and a thin one at that, maybe 2 or 3mm of wear layer. Straight away, the belt sander was off the cards. Too aggressive. One pass too deep, and we’d be looking at the backing board.
To make things worse, the client had already had a go themselves. A few areas had been attacked with a hand belt sander, leaving low spots and thin patches scattered across the room. It was going to be a delicate job.
I went for the Bona Speed System — 50-grit Platinum ceramics to start, followed by 80-grit Green ceramics, and finally 120-grit diamonds before coating. It was going well until the final area. As the 80 grit made its pass, the colour of the oak started to fade… then vanish. I knew instantly we’d hit the backing. Abrasives can be found in the link below.
Bona Platinum Ceramic Abrasives
Bona Green Ceramic Abrasives
Bona Diamond Abrasives
Once you see that, there’s no coming back. You can sometimes disguise a small spot with wax or fine detailing the sort of trick a French polisher might use, but this was beyond that. Still, the rest of the floor looked solid, so we carried on.
Next came Bona Classic UX primer, rolled on with a Bona SuperCoat roller. Normally, it’s dry within an hour or two, but this time, even after three hours, it was still tacky. The room temperature was fine, but something was off. Then it clicked, no airflow.
I cracked open both doors to let air pass through, and within twenty minutes the primer had completely dried. A good reminder that even the best products need ventilation to perform as they should.
But that wasn’t the last surprise. While inspecting the coating, I noticed one board with a huge bubble right through the middle. And peeling on the edge, the veneer had delaminated, lifting clean away from its backing layer. It was likely caused by that ultra-thin veneer reacting to the water in the primer.
Nightmare moment.
Rather than panic, I decided to fix it. I cut a small slit in the bubble, injected Lecol wood glue, pressed the veneer flat, and laid a piece of wax paper over it with a heavy weight overnight. The next day, it looked ten times better, and luckily, the client mentioned they were planning to put a rug there anyway.
The real key, though, was communication. Before the job even began, I’d explained the risks of sanding engineered floors, especially after a DIY attempt. So when these issues cropped up, they understood it wasn’t negligence and a risk of going through the wear layer, or we don’t and still see some of the damage, it was the nature of the material. That honesty-built trust, and they appreciated that.
In the end, the floor looked great. The finish was smooth, clean, and well-protected with Bona Mega matt lacquer. Only those of us in the trade would ever notice the small imperfections. Unless you have a Post-it note client!!
The takeaway? Engineered floors need to be approached carefully. Know what you’re dealing with before you touch a machine. As the years go on, wear layers are getting thinner. Check the wear layer, plan your system, and never underestimate how fast a floor can disappear beneath your sanding discs.
And once it’s done, remind the client how to care for it: pH-neutral cleaner, minimal water, and a good microfibre spray mop. The simplest habits can make all the difference in keeping that finish looking its best.
Because sometimes, success isn’t about perfection, it’s about awareness, communication, and a steady hand when the unexpected happens. Stuck on a job or had an experience like this before? Send in your nightmare to me at hello@ultimatefloorcare.co.uk