1 year old condo - damp problems

On 2/3/2019 at 11:30 PM, blackcab said:

It's more than likely either (1) damp from incorrectly installed bathroom tiles, floor or waste water drain, or (2) leaking pipework buried in the walls, or (3) incorrect external levels.

Yes for houses but the OP says he's on the 5th floor, so presumably item 3 wont be an issue. Unless behind the damp walls is a balcony with the slope going the wrong way (not impossible here: mine does).

The other thing that I find odd is that the OP mentions several walls in several different places, so that makes bad bathroom tiling unlikely.

Either way, having lived for many years in very old farmhouse it certainly looks like rising damp to me. So possibly some sort of water leak or ingress under the tiles which is rising up at the only permeable point: the walls.