Mold in a bathroom usually starts somewhere you do not look every day: the cabinet under the sink, the bottom of the wall behind the vanity, or a closet that shares a wall with the bathroom. By the time a spot shows up where you can see it, it has often been growing in the dark for a while.
This post covers why bathrooms grow mold, what we found on a job in east Ventura where a leak from an upstairs bathroom reached the bathroom below, and when bathroom mold is something you can clean up yourself versus something that needs containment.
Why bathrooms are where mold shows up first
- Leaks you cannot see. Supply lines, drain fittings and shutoff valves sit inside the vanity and inside the wall. A slow drip can run for a long time before anyone opens the cabinet.
- Water from the floor above. In a two story home, an upstairs bathroom sits over the rooms below. When it leaks, the water can travel down inside the walls.
- Steam and poor ventilation. Showers put moisture in the air every day. Without a fan running, it settles on the ceiling, grout and caulk.
- Materials that hold water. Cabinet bottoms, drywall and baseboards soak up water and stay damp.
The EPA’s guide to mold and moisture puts it simply: fix plumbing leaks and other water problems as soon as possible, and dry water damaged areas within 24 to 48 hours to prevent mold growth.
What we found on a bathroom mold job in Ventura
This job was a two story home in east Ventura. The homeowner called about mold from a leak that came from the upstairs bathroom into the downstairs bathroom. There was mold under the bathroom sink, on a wall in the dining room and in one closet, and she was not sure whether the leak was still active.
September 17: readings throughout the house
The first visit was about finding out how far the water went. The photos show a handheld meter held against walls, baseboards, the tub surround and closet walls in room after room, and the rooms being measured.
September 23: containment and opening up
By September 23, plastic containment was up in the affected rooms, taped down along the floor, and the flooring had been pulled up. Equipment was running inside the containment.
The cabinet under the bathroom sink is where the mold was easiest to see. The bottom and sides of the cabinet were covered in dark spotting, heaviest in the back corner where the cabinet meets the wall. The wall behind the sink was opened at the supply valves and the drain. Where walls were opened at the plumbing, the bottom plate, the piece of framing that sits on the floor, had debris and dark staining around the pipes.
The containment was still up on September 30.
October 9 to October 16: putting it back
By October 9, new flooring was down and the wall at the plumbing was still open. On October 15, new drywall went in where the walls had been opened, including in the bathroom. By October 16, the patched walls were textured.
Signs of mold in a bathroom
- Dark spots on the floor or sides of the cabinet under the sink
- A musty smell when you open the vanity
- A cabinet bottom that is swollen or soft
- Peeling paint or bubbling at the bottom of the wall
- Baseboards that are stained or pulling away from the wall
- Spots on the ceiling or grout that come back after you clean them
- Stains on the ceiling of the room below an upstairs bathroom
If the stain is on the ceiling below a bathroom, our post on water damage on the ceiling covers what it usually means.
Surface mold vs. mold in the walls
Not all bathroom mold is the same problem. Spots on grout, caulk or the ceiling over the shower usually come from steam. For damp bathrooms where mold keeps coming back, the EPA says increasing ventilation, like running a fan or opening a window, and cleaning more often will usually prevent it from recurring, or at least keep it to a minimum.
Mold under a sink or at the bottom of a wall is different. It means water got somewhere it should not be, and it usually goes past what you can see. Wiping out the inside of the cabinet does not reach the back of the drywall, the bottom plate or the subfloor. That is when the wall has to be opened. Our posts on mold behind drywall and mold on a subfloor go into what happens next.
Can you remove bathroom mold yourself?
Small surface spots, usually yes. The EPA says that if the moldy area is less than about 10 square feet, in most cases you can handle the job yourself. It also says bleach is not recommended as a routine practice during mold cleanup, and that you should never mix bleach with cleaners that contain ammonia.
Get it looked at when:
- The mold is inside a cabinet, wall or floor, not just on the surface
- It covers more than about 10 square feet
- It keeps coming back after cleaning
- You do not know whether the leak is still active
- The bathroom is upstairs and there are stains in the rooms below
How to keep a bathroom from growing mold
- Run the bathroom fan or open a window when you shower.
- Open the cabinet under the sink every so often and look at the bottom of it and the pipes.
- Know where the shutoff valves are under the sink and behind the toilet.
- Fix drips at the faucet, supply lines and drain right away.
- Keep an eye on the ceiling below any upstairs bathroom.
Our post on preventing water damage at home has more checks like these.
FAQ
Why does mold keep coming back in my bathroom?
Usually because the moisture is still there. On the surface, that is often steam with no ventilation. Under the sink or at the base of a wall, it is often a leak that has not been found or fixed. Cleaning the spot without fixing the water will not stop it.
Does painting over bathroom mold fix it?
No. Paint covers the stain, but the material underneath is still damp and the mold is still there. Find and fix the water first.
Does homeowners insurance cover mold in a bathroom?
It depends on the policy and on what caused it. Mold from a sudden leak is often treated differently than mold from a slow leak that went on for a long time. Our post on water damage and insurance coverage covers how that usually works.
How long does bathroom mold remediation take?
It depends on how far the water went. On this job, it was about a month from the first visit on September 17 to textured walls on October 16. A small area under one sink takes less time.
Seeing mold in your bathroom?
Total Restoration handles mold remediation in Ventura and across Ventura County, Santa Barbara County and Santa Clarita. We find where the water came from, contain the area and remove what needs to come out. Contact us to get it checked.