Mildew on Bathroom Ceilings Before Repainting

Two ceiling spots that look the same can be mildew growing in the film or just dirt on top of it. Before a repaint of a bathroom ceiling in Carlsbad, CA the crew treats the cause first, and the intervals interior painting carlsbad o faolains uses between cleaning and priming are longer than the can instructions suggest, because mildew comes back through paint that went on too soon.

Telling mildew from dirt

A drop of household bleach solution on the spot settles it. Mildew lightens within a few minutes, while dirt stays put. Mildew follows the coldest parts of the ceiling, the corners, the line above the shower and the area around a weak fan. Older cottages and bungalows in the northwest of Carlsbad often have a small fan or no ducting, so the same spots return every winter.

Cleaning and killing the growth

The ceiling is washed with a mildew cleaner, kept wet for the time on the label, then rinsed and left to dry fully. Dry time in a fog belt home near the lagoons runs longer than inland, so a room that feels dry after a day may need another. Rushing this step traps spores under the new film, and they show through within weeks.

Stain blocking the marks

Stains remain after the growth is dead, and ordinary latex will not hide them. A stain blocking primer, oil based or shellac, locks them in. Small ceiling cracks and peeled tape joints are repaired with spackle, sanded and spot primed first, so the surface is even before the full primer coat goes on.

Mildew resistant finishes

A mildew resistant acrylic ceiling paint carries a film additive that slows growth. Flat is common for ceilings because it hides roller marks, but in a wet bathroom a flat that is formulated for moisture, or an eggshell, wipes down better. Two coats applied at the stated coverage give enough mil thickness for the additive to work, and a thin coat defeats it.

Fixing the reason it came back

Paint treats the symptom. A fan that exhausts outside, a run time that keeps the fan on after the shower stops, and a slightly open window on dry days do the actual work. A crew should point out an attic duct that is disconnected, since the paint will fail under that condition no matter what is used. A bathroom that sees fog drift through an open window in summer and heavy rain in winter should be checked again a few weeks after the finish coat, when any returning spots show first.