ᐅ Laminate Flooring on an Uneven Subfloor?

Hello dear forum community,

I would like to ask for your advice.

We are currently having our attic expanded (apartment building constructed in 2000, maisonette apartment with potential for extension in the attic. The ceiling between the two maisonette floors is a beam construction). The developer had already installed a 22mm (about 7/8 inch) chipboard subfloor (tongue and groove) on top of the beams for the previous owner, then a similarly thick insulating mat (looks like glass wool) on top of that, followed by another floating 22mm (about 7/8 inch) chipboard subfloor (tongue and groove, each with about a 1 cm (0.4 inch) expansion gap at the wall). I do not know whether the lower subfloor is screwed to the beams.

Now we want to install a floor and have decided on laminate (Tarkett Woodstock 832). Underneath, as impact sound insulation, we are using ewifoam Silenza 5 mm (about 3/16 inch), an XPS insulation material. The 5 mm thickness was chosen so that the floor height will align well with the top stair step later. The material is already at our house, bought from a store that also referred us to the floor fitter. When this floor fitter came to start the work, he found that the upper subfloor is quite uneven: the individual boards have warped upwards along the longitudinal edges by about 5 mm (about 3/16 inch). When walking on the edges, you can clearly feel the floor give or rock slightly at these points.

The floor fitter now tells us that he cannot install laminate on this, or if he does, he will not provide any warranty. In his opinion, the tongue-and-groove connection of the laminate will eventually break because the floor is so uneven. He says sanding is pointless because the problem is too widespread. He believes the cause of this unevenness is that the subfloor boards absorbed moisture, possibly from the paint that was applied to the wallpaper a few weeks earlier.

We sent him back for now and are quite confused and uncertain. Is the situation really as serious as he describes? Of course, we do not want a floor that rocks with every step and might tear apart. But are there better solutions than simply saying he will not take responsibility?

Would it be conceivable to screw all the upper subfloor boards to the lower ones, so that the floor is essentially “forced flat”? But then it would no longer be a floating floor. Would that cause other problems?

Or should one try to compensate for the unevenness when installing? What happens if the floor warps again afterward?

Thank you for your opinions and tips.

Unfortunately, there is no other choice but to try to level the floor somehow. If you want to do it properly, in this case you will either have to invest a lot of money or alternatively put a lot of your own time into the renovation.

Good morning,
I am currently installing new laminate flooring as well. The subfloor is uneven, so I laid down chipboard panels. I read about this here beforehand and followed that advice. It was definitely worth it because the laminate lays perfectly on top. Using anything else is a bad idea and only results in double the work and double the cost.

Best regards

I’m familiar with that, too, and our attic room has a similar issue where the floor is uneven. I also installed chipboard panels and filled the joints with filler. Then I laid the laminate flooring on top. I hope it lasts forever. 🙂

What surprises me here is that the flooring installer did not notice this beforehand. When I hire someone for a job, they need to inspect the floor first. That way, they would have found that the floor is uneven. Action could have been taken earlier.

Now saying that no warranty is accepted is weak.

Sometimes defects only become apparent during the work. This is not uncommon. But he still noticed it in time. Others would have installed the laminate flooring and taken the payment.

After a short time, the edges of the laminate would have started to split.