Excavating A New Basement - There are several ways to help prevent moisture damage issues in a cellar. The very first rule of thumb is no dirt basements. Although these are less common in this day in age, it's a good idea to point out that dirt flooring not only hold a huge amount of moisture but also can give off a variety of gases. When building a cellar, make certain that you've got a floor drain with a trap installed in the lowest point of the ground.
Without a floor drain, any water that's spilled inside can't escape. If necessary, install a sump pump and make sure the sump cover is tightly sealed. Sump pumps are often used where flooding due to a high water table may be a problem. Additionally, waterproof the exterior of the base walls and install a perimeter drainage system. An often overlooked problem in bathrooms is moisture that comes from humidity.
The easiest way to control humidity is to exhaust water vapor produced in the home to the exterior. Signs of high humidity include condensation on windows, pipes or other surfaces as well an overall sense of moisture in the atmosphere, dampness, and odors. Often, the humidity will be caused by exposing the cellar to external air (open windows), having wet laundry hung to dry in the cellar, keeping firewood in the cellar, and/or a drier vent that exhausts inside.
To decrease humidity, there are several things a homeowner can perform: install energy-efficient windows, insulate walls and cold water pipes, prefinished flooring if at all possible, run drier vents to exhaust directly outside and don't dry laundry or firewood in your cellar. In summer, use a portable dehumidifier or air conditioning to decrease humidity. In warm, humid weather, maintain cellar windows shut. The key to keeping basement humidity is to keep them well ventilated and keep extra moisture out of the cellar.