Before installing carpet in your basement, you need to seal the basement floor. If the floor has not had a sealer applied prior to installation, expensive problems will arise in the future. Any moisture seeping through the concrete from the ground will cause the carpet to dampen, eventually rotting both your carpet and padding. Moisture in the carpet can cause serious mold issues in your home, which can be detrimental to your family's health.
It's also quite expensive to repair. Mildew and bacteria growth are other concerns. Avoid these problems by sealing the floor.