All bathrooms are humid during baths and showers, but how long they stay humid is what determines whether or not the bathroom is excessively wet. Opening your bathroom windows and turning on a ventilation fan should get the bathroom, and the grout in the bathroom, dry again within an hour. If the bathroom and the grout outside the shower do not dry out, it is a sign that the bathroom is too wet.
Several issues are related to humidity in your bathroom. Overly humid bathrooms will attract mold spores, which can grow all over your bathroom walls, shower curtain and ceiling. They not only look bad and can decay your bathroom, but they also can actually cause health issues for certain people. If your grout stays wet for several hours, its porous surface will eventually attract mold spores that can grow into visible mold growth in as little as 24 hours. Overly humid bathrooms also can encourage wood rot and drywall decay.
Prevent the grout from staying wet for a long time by installing a better ventilation system in your bathroom. After a shower or bath, turn on the ventilation system and shut the bathroom door, which will make the ventilation more effective and will prevent moisture from going throughout the rest of the house. If this is not enough to dry the grout, install a small dehumidifier in the room near the wet grout and turn it on when needed.
Once the wet grout attracts mold, it can spread throughout the bathroom. The mold spores will begin by eating the dust and dirt on the grout, but it will eventually devour the organic content in the cement grout, leading to grout decay. Prevent this by removing the mold and cleaning the grout. To do this, mix 1 cup of bleach per gallon of water, and scrub it over the grout until it is completely clean. Rinse the area, and dry it completely once you are finished.