I am going to install a laminate floor. I bought a 5 mm thick underlayment and foil. But when I removed the old carpet, I saw a large number of cracks and height differences. There is a 4-5 mm depression in the middle of the floor.
Does the floor need to be leveled with a self-leveling filler, or should the underlayment hide all these irregularities?
Take gypsum plaster, prime the floor and pull through the plaster. The underlayment does not compensate for the differences.
If 5mm is the maximum height difference, and less in other places, then I would recommend just laying the laminate on the subfloor, no extra work.
We had a similar situation, 2-3mm unevenness. It's been 2 years since the laminate was laid, nothing squeaks or falls off.