Mold and Mildew

• Musty odors in the home are most often associated with mold and mildew growth as a result of excess moisture. The odor itself is the least serious effect. If allowed to persist, mold and mildew can cause extensive damage to your floors themselves and the materials underneath the floors. Some specific species of mold can also exacerbate the symptoms of people with asthma and other chronic breathing conditions. All these potential problems underscore the importance of controlling indoor moisture as soon as you notice a musty smell coming from your wood floors.
  
  

Identifying the Source

• There are many possible ways that excess moisture can make its way to the area underneath your wood floor. If there isn't any insulation between the floor and the layer under the floor, excess moisture on concrete, subflooring or underlayment can cause mold and mildew growth on the floor itself. Even overly moist soils can impart moisture to floors built above them through water vapor transmission.
  
  

Controlling Moisture

• Prevention is the most effective way of avoiding problems associated with wood floor moisture. If they are available to you, buy wood flooring materials that are treated with anti-stain or sap stain fungicides, as these chemicals will help prevent mold growth even in the presence of excess moisture. Homeowners sometimes use a layer of insulation between concrete subfloors and wood floors to help control moisture, but in the case of wood floors, this approach can be counterproductive by trapping the moisture inside insulation where it can still cause problems. Instead, exterior moisture drainage and exterior insulation are preferable.
  
  

Eliminating Mold

• Of course, if mold and mildew are already growing underneath your wood floors, you will need to act quickly to contain the problem. Any visible mold growth above the floors where people or animals could contact it can be washed with a bleach solution and then dried. Removing mold growing underneath your floors will likely require removing the wood flooring itself. This may seem a drastic and costly option, but note that repairing damage caused by the excess moisture -- such as warped wood and waterlogged insulation -- will itself require removing the wood floors temporarily.