I have visited a HDB. one bathroom ceiling is like this. Initially I was thinking it is definitely water leakage from upper floor. But after I walk around the whole unit and I changed my mind. Probably it is due to moisture. Now I am guessing the water proof at upper floor is fine.
The reasons are below. Anyone comes with any idea? Is it a high risk to take this unit?
1. The mark seems are equally array and formed by small dots. The portion next to the bulb is better. The portion above the shower is worse. The worse portion is just located at the corner with pipe.
2. The design/location of this bathroom makes ventilation worse. window is 45 degrees connected to service balcony and air flow is not passing straight.
By the way. Is that possible to hack/replace the floor tiles and do water proofing but keep the wall tiles? Because the wall tiles are still in good condition.