Laminate floors are “floating” floors, and as such, are not fastened to the subfloor. That actually makes the condition of the subfloor more critical to the success of your installation. Left unleveled, a subfloor that isn’t smooth and flat could cause your laminate flooring planks to squeak or separate.When you check how level your subfloor is, you’re looking for a peak or valley more than 1/8 of an inch within 40 inches of grade. These subtle differences can sometimes be hard to spot just by looking. Here’s our favorite way to determine whether the subfloor is level, and what to do if it isn’t level.1. Take any laminate plank and lay it on its end, dragging it across the subfloor. As you find a low spot, mark it with a green marker; find a high spot, mark it with a red marker.2. Once you’ve determined the low and the high spots, you’ll want to even out those differences. We recommend using a Portland-based leveler or leveling compound to fill in and grind down the peaks. Allow the leveler to dry overnight before beginning installation.As with any product, always read the complete leveling compound instructions first.The goal while thinking about leveling the subfloor is to have a clean, smooth and level surface upon which to install Swiss Krono laminate flooring. Remember, laminate flooring with attached underlayment padding can accept a deviance of 1/8 of an inch over 40 inches. Any low spots of 3/16 of an inch or greater must be filled in with leveling compound.