Clean gutters and a sound roof will help prevent rain and snowmelt from leaking into your home. But a trip to your basement during a downpour may reveal that water is still finding a way to seep inside.

Water entering your basement is more than just unsightly. It can easily damage any items you have stored nearby, cause the foundation to crack and settle unevenly, and allow mildew and mold to form.

If your basement is particularly susceptible to water infiltration, you can take steps to waterproof it. These methods will help preserve the strength and air quality of the basement, and can be particularly helpful if you want to turn the room into a finished area.

Since waterproofing the basement can be a costly process, you should first make sure that water is coming in from outside the home. Jeanne Huber, writing for the National Association of Realtors' home improvement site HouseLogic, says moisture in the basement might be a result of high humidity levels. If you tape a square of aluminum foil to the wall and the moisture is not on the side facing the wall, the issue is humidity rather than a leak.

You can also look around the home to see if you can take any steps to direct water away from your home. The magazine Family Handyman says the yard around your home should be properly graded, and your downspouts should also be expelling water a sufficient distance away from your foundation.

Even if your exterior drainage is in good order, leaks can persist in other ways. Matthew Stock, writing for U.S. Waterproofing of Rolling Meadows, Illinois, says water can be pushed into your basement through hydrostatic pressure as the water table rises. Water can also enter through lateral pressure, which occurs when the soil around the home drains poorly, expands as it absorbs water, and presses against your foundation.

The more inexpensive repair options will tackle the problem from inside the home. Oseye Boyd, writing for Angie's List, says sealants and epoxy injections can be used to plug cracks and stop water from entering. The North American Retail Hardware Association says cracks larger than one-eighth of an inch wide should be patched before you add any other waterproofing materials.

Once the walls and floors have been sealed, you can paint a waterproofing compound on them to add further protection against leaks. Huber says these options include concrete coatings and waterproofing paint.

Plastic sheeting and moisture barriers can keep water from damaging items in your basement, but won't stop the leaks. If you use this method, it is best to combine it with other waterproofing methods.

In some cases, the water intrusion may simply be a result of an opening at the cove joint, which is located between the basement wall and floor. The North American Retail Hardware Association says this gap can be repaired fairly easily. You may need to cut a dovetail joint at the juncture between the wall and floor to better hold the mortar; once you have completed this process and cleaned the area, you can seal it off.

More persistent basement leaks may require you to invest in a drainage system. A sump pump and French drain will actively remove water from the basement, but they are quite costly to install. The magazine Family Handyman says the process will require you to dig up your basement floor, and can result in a bill of several thousand dollars.

Waterproofing the basement from the exterior is another option. In this process, the ground around your foundation will be excavated down to the depth of the basement floor. Huber says contractors can then add a waterproofing material to the exterior of the walls, along with a drain to direct water away from your home.

This option is very effective, but is also the most expensive one. Boyd says the work typically costs $20,000 to $30,000, but can be even pricier if it is difficult to access the foundation. The excavation can also require you to remove and reinstall landscaping or other features of your yard.