This is usually caused by a leak somewhere.
Water leak in garage ceiling.
If the water is dirty or stains the ceiling the source might be a leak in the roof.
A possible cause of a ceiling leak in a two story house is an upper floor bathroom.
The ceiling is above the bathroom 2 bedrooms a hallway and a hall closet.
If you caught it in time you can see water running down the wall and into your garage.
It can be anywhere from the roof to the windows.
Then i noticed that most of the garage ceiling is streaked with brown water spots and in many areas the ceilng is buckling soft to the touch.
Big buckets will also come in handy for heavy leaks.
A whole home humidifier or similar water leaking appliances installed in your attic can also cause water damage to the ceiling as well as leaking bathroom failed bathroom waterproofing fridges or other kitchen appliances on higher floors.
In order to solve water leaking into the garage under the wall you have to find the source of.
Protect your floor from moisture by laying down towels and old newspapers on them.
You can t just allow water to come in contact with your furniture electrical appliances flooring or walls in the event of a ceiling leak.
Water leaking into the garage under the wall.
Gain access to the attic and with a flashlight find the place where the ceiling is wet between roof joists.
Screw type fittings especially in drain traps are more likely to leak than are glue type fittings.