We have hardwood floors in our new home.  We placed a mat on the floor of a home office to protect the floor.  When the mat was moved to clean the floor, it gave off a musty-mildewy odor that overwhelmed the room.  The floor was cleaned several times but the mold odor persists.  Since I am asthmatic and sensitive to mold, I need to know what to do to resolve the problem.-Anon

 

            In this case the homeowner was advised by a syndicated columnist to contact the hardwood flooring materials manufacturer for advice.  This seems reasonable as one would expect the manufacturer/manufacturer’s representative to have special technical knowledge of the kinds of problems homeowners have experienced with their and how they can be resolved.

            In this case it is unlikely to be a product defect, more likely the problem developed after the flooring was installed.

            Hardwood flooring varies from simple oak (or other wood) tongue and groove boards that are installed over a base flooring or concrete slab to a multi-ply material with the bottom ply cut to give the floor some flexibility.

            The description of the problem given by the homeowner indicates that the mat was made from the same-type of cellulose-containing material which became infested or plastic that contributed to high moisture levels at the interface between the wood flooring and the mat.  The continued presence of the odor indicates that the flooring material has become infested.  As such the finish coat’s integrity has likely become compromised allowing the odor to come through.  If this is the case the surface under the mat will likely need to be refinished to lock in the infested material and block the odor. 

            Unfortunately, the moldy-musty odor under the mat may only be the tip of the iceberg.  I recently conducted an investigation of a house that had a variety of mold concerns.  After conducting wall moisture readings, I determined that it would be desirable to conduct moisture readings of hardwood flooring near to wall areas where some water intrusion problems were occurring.  Moisture readings were in the 16-18% range (actual scale) and unacceptably high.

            Most unusual was the fact that similar readings were observed on all hardwood floor surfaces in a hallway, kitchen, dining room, and living room.  High readings were observed at considerable distances from walls indicated that water intrusion was not the primary cause of the elevated moisture readings.

            The hardwood floor was a multi-ply type that was five years old.  It appeared as if it was heavily worn despite the fact that there was little people “traffic” over it.

            The worn appearance can be seen in the adjacent images that show the floor compared to a piece of flooring material that had not been installed.

               The observed “wornness” is likely due to discoloration caused by high wood moisture levels that have occurred over the past five years of the house’s history.

            The question is “where is the moisture coming from.”  Obviously it has to be coming from the below the flooring.  In this case the floor base is slab concrete.  If there is inadequate site drainage, water could be wicking up from the ground below causing the hardwood flooring to take up moisture (This assumes that no polyethylene barrier exists below the slab to prevent such upward liquid/vapor water movement).

            An alternative explanation is that water is condensing underneath the flooring because of cool ground and slab temperatures.

April 23, 2004

Indoor Environmental Quality (2000), Thad Godish Ph.D., C.I.H

Direct E-mail 00tjgodish@bsu.edu