A stain on the ceiling under an upstairs bathroom is one of the most common ceiling problems in Diamond Bar's two-story homes. A contractor pins down which fixture is leaking, gets it fixed, and repairs the ceiling below.
Many of the two-story tract homes built in Diamond Bar through the 1970s, '80s and '90s put an upstairs bathroom directly over a family room, kitchen or entry. That stacks the plumbing neatly, but it also means a slow drip from a shower pan or toilet seal lands on the most visible ceiling in the house.
A stain directly under an upstairs bathroom that darkens or spreads after someone showers or flushes, and fades a little in between.
Bathroom leaks are usually slow and intermittent, which is why they're easy to ignore: wet after a long shower, dry by the weekend. That cycle is also what makes them dangerous. The drywall never fully dries, and mold often starts on the top side long before you see it.
Note where the stain sits relative to the room above, then use these clues.
A cracked pan or failed liner leaks every time the shower runs. A leaking valve can drip whether or not the shower is on. Water splashing past the door or curtain, or through failed caulk at the curb, soaks the subfloor at the entry side.
Clue: worse right after showers; stain near the shower's footprint or its entry side.
The rubber gasket behind the tub's overflow plate and the drain connection underneath are classic slow leakers, and they only leak when the tub is filled high or drained.
Clue: stain near the tub's drain end; appears after baths, not showers.
A toilet that rocks has usually broken its wax seal, and every flush pushes a little water onto the subfloor. A weeping supply line or tank bolt drips constantly.
Clue: stain under the toilet's position; a toilet that moves when you sit on it.
A loose slip-joint on the P-trap or a worn compression fitting under the vanity drips into the cabinet and down through the floor.
Clue: water or swelling inside the vanity cabinet; stain under the sink's position.
Stain not under a bathroom, or none of these brought it back? The guide to finding where a ceiling leak is coming from covers roof, AC and supply-line leaks too.
The questions that come up when the stain is under the bathroom.
Look at where the stain sits relative to the bathroom above and when it gets worse. A stain that darkens right after showers points to the shower pan, valve, drain or the door side of the shower. One that grows slowly whether or not anyone showers, often near the toilet's position, points to the wax ring or supply line. Running one fixture at a time while someone watches the ceiling narrows it down.
Only if the grout or caulk is the actual problem, which is less common than people hope. Failed caulk at the door, the curb or the tub edge does cause leaks. But a cracked shower pan, a leaking valve or a loose drain won't be fixed by new grout. It's worth confirming the source before spending money on the tile.
Not usually. Drain and valve leaks can often be repaired from the ceiling below, through the opening that has to be made anyway. A failed shower pan is the exception: replacing a pan generally means removing the tile floor of the shower.
Not the fixture that's leaking. If it's the toilet, shut off its supply valve and use another bathroom. If it's the shower, don't use it until the source is confirmed; other fixtures in that bathroom are usually fine.
The leak source is plumbing or tile work; the ceiling below is a ceiling contractor's job. For the plumbing, the plumbing work is handled by the right trade and scheduled so it's done before the ceiling is closed. It's scheduled so the ceiling stays open until the repair upstairs is tested, then closed up.
Only after you're sure the leak has stopped. Bathroom leaks are often intermittent: dry for a week, wet after a long shower. Paint over a stain that's still being fed and it comes right back, sometimes with mold behind it.