Does self-leveling grip on the membrane?
When tested, the Warmup membrane was able to grip to self-leveling.
Flexible self-leveling can be used so long as it is a minimum thickness of 3/8” (10 mm) in a single pour from the top of the castellation to the top of the self-lever. Which essentially means a ½” pour.
The self-leveler will state if it is compatible with plastic/vinyl floor substrates on its instructions. We always recommend confirming this before starting.