It s a bit confusing but a flat floor can still be slightly out of level and still create a good foundation for a long lasting floor installation.
The floor is croked.
But laying out the laminate floor layout pattern ahead of time can still be complicated especially in an older home with out of square walls.
The likelihood a given floor has for bending is affected by many factors but the most common primary cause is simply old age.
A plywood subfloor will bridge any minor waves in the existing floor and leveling compound would help too.
Some new flooring installations require a level subfloor such as resilient tile flooring.
A new floor design that satisfies code requirements for bearing capacity and rigidity resistance to bend may still be appreciably sloped after many years of service.
The floor can have an unlevel subfloor and still have a base for a nice laminate floor.
Laminate flooring on an uneven subfloor can cause problems and needs to be addressed.
If the wall isn t straight and you start a full course of flooring against it then the whole floor will look crooked.
How to determine if a floor is level.
Laminate floors aren t attached to the subfloor but subfloor preparation is as critical as it is when installing a nail or glue down floor.
You will have to make sure your joists can handle the addition of considerably more weight from the plywood subfloor and any floor coverings.