Mold is a fungus that grows in cool, moist areas in a home like basements, attics, bathrooms and laundry rooms. It poses a health risk to people with weak immune systems and is an irritant for asthma or allergy sufferers. Mold is generated by airborne spores and can grow on all kinds of surfaces: ceilings, walls and floors. It can even grow underneath floor coverings. It can be removed from a floor, but it is a time-consuming task.
Take up the floorboards. If the mold has spread to the majority of the floorboards, discard them and purchase new floorboards.
Find the source of the mold, like a crevice or hole that allows cool, outside damp air to seep into the home. Patch the crevice or hole with plaster and seal it with a fungicidal sealer to prevent future mold growth.
Clean the floorboards, if they can be salvaged, with warm soapy water. While the floorboards are up, wash them and allow them to air dry in a warm, dry environment. Then wipe them down again with distilled white vinegar to eliminate any remaining mold spores; air dry.
Prevent future mold growth by using a dehumidifier to dry out excess moisture in the house.