When not installed on a level surface a luxury vinyl plank floor can shorten in length when it rides over high and low areas and it can also lift on edges or ends where a substrate irregularity.
Luxury vinyl plank not sitting flat.
Even though the first reason for the invention of vinyl planks was to mimic hardwood floors today it authentically mimics different textures colors and species.
During installation run a vapor barrier under the vinyl plank flooring to help prevent.
The luxury vinyl materials are less likely to buckle than some of the less expensive economy tile floors.
Vinyl plank flooring over radiant should not be a problem provided you follow the manufacturers recommendations.
Your floor is not flat so the flooring is holding itself up by it s own will and when you walk on it you are pressing it down into those valleys and it s touching the concrete.
That is my semi educated guess.
Level is not necessarily important.
After all a floor can be flat and have a plane to it.
Primary issues arise in some systems with uneven surface temperatures causing the flooring the react inconsistenly to the wide changes in temperature.
Vinyl plank is water resistant and is not like hardwood which is not resistant to water.
And i don t like it.
You can seal vinyl plank completely and prevents moisture from going into the floor.