Origin of the Smell

• All homes will smell a little stale when they have sat vacant for awhile, especially basements where the outside air does not normally reach. Insulated basements especially do not get much airflow since any cracks will be filled up by the insulation material. To help determine the smell and to see if it is covering up something more serious, open all of the windows in the basement, keeping them open all day. Pick a day when it is not raining outside since the wet weather may only contribute to the problem. If opening the windows does not clear out the musty smell, you know that you have a mold problem, whether great or small.
  
  

Wet Areas

• Once you have determined that the musty odor is coming from mold, you must first look for areas of moisture in the basement since areas that stay moist a good portion of the time lead to mold growth. The areas around the windows in the basement often are the entry point for moisture. Look for any bubbling or peeling paint on the walls since this will also indicate a presence of moisture. If the basement has a bathroom or laundry area, check around the faucets, toilet, drain and grouted areas for signs of mold growth. Feel the carpets as well. Black or yellow spots on any surface in the basement can also indicate the presence of mold.
  
  

Source of the Water

• You can clean the mold out of the basement, but if you do not first find the source of the moisture, the mold growth will only continue. Cracks in the house's foundation, which you can see from the outside, can let moisture seep behind the finished walls. Pay attention to any gaps around the windows, as well as cracked window panes, and use silicone caulk to seal up anything you find. Any holes or gaps in general around the exterior of the house can lead to moisture entering the house. Water that comes up through the floor of the basement can be combated by installing a sump pump.
  
  

Mold Cleanup

• Cleaning up mold requires a lot of care since you can spread the mold spores if you are not careful, potentially spreading the mold further and putting your health at risk. If you are not comfortable with taking the process on yourself, seek a mold removal service. Whether you clean up the mold or hire a service, you must get rid of the mold before it spreads to the point it damages more of the basement, including floor joists or other structural features.