No the tiles are not drummy.

The bathroom is close to five years old (same age as the building). The stall itself has small 1" tiles.

Thank you for the reply.
In your opinion (given that the structure is ok), would the dehumidifier even help or be necessary? Or sealing the grout would do?
Thanks

Hi,
One of the shower stalls in the apartment/condo was inspected by the home inspector and mentioned to have "water infiltration" (measured by the moister meter) behind the wall's ceramic…