Many basement water problems come from surface water leaking into the room. One primary cause of this is a clogged gutter. Because gutters clogged with leaves and debris can also cause roof and wall damage, it's important to get up there and clean them out every so often. Saving the basement from further flooding is a side benefit to this essential task.
It's a good idea to place extensions on the gutter downspouts. While a homeowner may not like like having her downspouts extending 10 feet away from the house, that is the distance needed to prevent water from draining back down toward the foundation of the house. If this is where a lot of water is coming from, an extended downspout could solve basement moisture problems in no time.
Over time, paved areas that come right up to the house can be the cause of wet basements. This is because the sealant in the intersection of the pavement and the house becomes cracked and rotted. Through this opening, rainwater can come in and flood the floor of the basement. Check this intersection and repair any cracks in the sealant that may have occurred.
A home in which the yard that slopes toward the house is a prime candidate for a wet basement. Surface water simply drains toward the house and any cracks or crevices in the basement walls will let water in to flood the floor. The best way to prevent this is to have the yard sloping away from your house, taking the surface water with it. Many times, this can be accomplished with an experienced landscaper, who can contour the yard so that it slopes away from the house.
Even if not a direct invitation to rain flooding the basement, keeping doors and windows to the basement open will let humidity build up in the room. This won't lead to a flooded floor, but it will make the basement dank and damp, which can lead to all kinds of moisture problems. Mold, mildew and the gradual destruction of any furniture or paper in the basement can occur with high humidity levels.