What's usually above a stained ceiling
- Upstairs bathrooms — failed toilet wax rings, tub drain leaks, and shower pan failures drip slowly for months before the stain appears.
- HVAC in the attic — most Mesquite two-stories and many single-stories keep the air handler in the attic. A clogged condensate drain overflows the pan right onto the ceiling below, especially in peak summer.
- Roof penetrations — around vents, flashing and valleys after hail or wind events.
- Pipes — supply lines routed through the attic, vulnerable in freezes.
Why you dry the cavity before painting the stain
Painting over a water stain without opening and drying the cavity traps moisture against drywall paper and framing — the exact recipe for mold growth you can't see. Proper repair: locate and fix the source, open or dry the cavity (often from above via the attic), verify with a moisture meter, then patch, texture and paint.
If the ceiling is actively bulging: put a bucket under it and relieve the water with a small screwdriver hole at the low point of the bulge. A ceiling that drains slowly through a small hole is repairable; one that collapses under water weight takes the insulation and sometimes light fixtures with it.