Bathroom Mold: When It Is Just Grout and When It Is Inside the Wall

Surface mildew or real mold?

A bathroom is the wettest room in the house, so some growth is normal. Black or pink spots on grout, caulk, the shower curtain or the tile itself are surface mildew. Tile and glass give it nothing to eat, so it wipes off with a bathroom cleaner and a stiff brush. If the caulk itself has gone black from the inside, cut it out and re-caulk.

It is a different problem when the growth is on something porous or hidden:

• Spots or gray patches on the ceiling, especially above the shower
• Paint bubbling or peeling on the wall next to the tub
• Soft or stained drywall around the tub, shower or toilet
• A musty smell under the vanity, or a warped vanity floor
• Loose tiles or grout that keeps cracking in the same spot, which often means water behind them
• Staining on the ceiling of the room below the bathroom

What causes bathroom mold

Nearly every bathroom mold job we see comes back to one of two things: steam that has nowhere to go, or a slow leak nobody noticed.

Steam is the common one. A shower puts a lot of water into the air, and without a working exhaust fan it settles on the ceiling and the outside wall every single day. Older Cincinnati homes often have no fan at all, or a fan that vents into the attic instead of outside, which moves the problem up into the attic.

Leaks are the hidden one. A failed shower pan, a cracked grout line, a supply line under the vanity or a toilet wax ring that lets a little water out with every flush can soak the wall or floor for months before anything shows.

What a bathroom mold job involves

Bathrooms are small, so containment matters even more. The spores have to stay in the bathroom while we work. Here is what our bathroom jobs include.

1. Seal it off. We close the cold-air returns nearby so the furnace cannot pull spores through the house, hang plastic sheeting over the doorway with a zipper door, and lay floor protection on the path in and out.

2. Get to the mold. The vanity usually comes out so we can see the wall and floor behind it, and the trim comes off. Drywall with mold in it gets removed, often floor to ceiling on the wet wall, and the ceiling drywall too when the growth is up there.

3. Clean the framing. Once the drywall is open, the wood studs get HEPA vacuumed, scrubbed with an antimicrobial cleaner and HEPA vacuumed again. A fog treatment reaches what a hand cannot.

4. Scrub the air. An air scrubber with a HEPA filter runs during the work and stays running afterward.

5. Seal the wood. A clear antimicrobial encapsulant goes on the cleaned studs before anything is closed back up.

6. Test. An air sample inside and one outside for comparison, sent to a lab. The walls go back up only after the test passes.

After the job, replace the furnace filter. It has been catching spores the whole time.

Keeping it from coming back

The fix that matters most is a bathroom fan that actually vents outside and runs long enough. A fan that runs only while you are in the shower leaves the room wet. Let it run for at least 20 minutes after you get out, or put it on a timer switch.

Then fix the leak if there was one: re-grout or rebuild the shower pan, replace the wax ring, or swap the supply line. Wipe the shower walls down after use, keep the door open when you can, and if you are rebuilding the wall, use moisture-resistant drywall or cement board behind any tile.

What bathroom mold removal costs

A bathroom job depends mostly on how much drywall has to come out and whether the vanity, ceiling or the room below are involved. Pick Bathroom in the cost box on this page to see what our bathroom mold jobs actually came to, from our own invoices. Putting the bathroom back together afterward (drywall, tile, vanity) is priced separately, and we give you both in writing before any work starts.