We had some rain and the outside humidity is above 72% usually in the 80ties.
On a number of occasions I have checked the humidity at level of the concrete floor and even after some heavy rain it stays at 50%.
I believe that there is already a DPM under the concrete.
For comparison the humidity on the 1st floor is usually about 10% higher than downstairs!? I know there is a bathroom but it is not used that much.