What Causes Mold and Mildew in a Bathroom?

A  pair of hands cleaning mo;d and mildew from a wall with a red sponge and a spray bottle.

Mold and mildew are among the most common problems in household bathrooms and can be a pain to get rid of. If any of your home's bathrooms have recently fallen victim to the formation of mold or mildew, you may be curious about the possible causes. Below is information on the leading causes of bathroom-based mold and mildew.

Improper Ventilation

Poor ventilation is one of the most common causes of mold and mildew in bathrooms. Most people tend to close their bathroom doors when the shower is in use, effectively trapping all the moisture-laden steam produced by hot showers in the bathroom. The moisture then attaches itself to the area's floor, walls and plumbing fixtures and, over time, gives way to the formation of mold or mildew. For this reason, it is recommended that you leave your bathroom door open when your shower is in use. In addition, you may want to place a window-mounted fan in one of your bathroom windows and set it to "exhaust" whenever you take a shower. This will help ensure that the aforementioned steam quickly exits your bathroom. To this end, if you're particularly concerned about bathroom-based mold or mildew, it's a good idea to abstain from taking excessively long showers.


Bathrooms are arguably the wettest areas in any home, largely as a result of all the plumbing fixtures contained therein. Even if your bathroom is sufficiently ventilated, all the dampness caused by the water used in sinks, showers and toilets will eventually give way to mold or mildew if not properly kept in check. Take care to thoroughly clean your shower, tub, sink and toilet at least once a week with the aid of various commercial cleaners and assorted cleaning supplies, such as scrub brushes, sponges and washcloths. Additionally, make sure to use very absorbent floor mats in your bathroom, as this will help ensure that the water you track after emerging from the shower doesn't find its way onto your tiled floor. Also, while it may seem cumbersome, make a point of never leaving wet towels or washcloths lying on the floor, as this can also be a precursor to mold and mildew in your bathroom.

Broken Grout

Deteriorating grout is another common cause of bathroom-based mold and mildew, which is why replacing your shower's grout once every 6 months is a very important step in keeping mold or mildew out of your bathroom. If your grout has begun to crack or chip, moisture from shower steam is easily able to find its way onto the sides and back ends of your tiles and produce mold or mildew deposits that can be very difficult to get rid of. In addition to protecting your bathroom from mold or mildew, regularly replacing your grout will give your bathroom a nice, clean feel. Alternatively, bathrooms with deteriorated grout tend to give off a very sloppy, unhygienic feel.