Floor Discoloration

From time to time, end users may complain that mats cause the floors beneath them to discolor. This complaint has applied both to carpet and hard surface floors such as vinyl or tile. The discoloration is usually a yellow or brown color.  The points below discuss some possible causes for these complaints.

Possible Cause of Discoloration: Moisture

  • Moisture from the ground comes up through the floor until it reaches the floor surface. This moisture normally evaporates and goes unnoticed.  However, placement of a mat on the floor prevents the evaporation, trapping the moisture, thus causing discoloration.  This seems to be most common at entrances where cold or warm air enters the building causing condensation (sweating).
  • Placement of mats on freshly cleaned and still damp carpet can prevent the carpet from fully drying, thereby causing discoloration.
  • If not properly dried and the back of the mat remains damp, that moisture can cause discoloration.
  • As mats age, perforations can appear and eventually increase in size.  Larger perforations can develop into slits and moisture can leak through to the floor beneath and cause discoloration.

Possible Cause of Discoloration: Chemicals

  • Yellowing can occur on a VCT (vinyl composition tile) or resilient floor. The best explanation for this is that the yellowing comes from chemicals that are in the floor that migrate to the surface over time. These chemicals are generally very small molecules that move within the molecular structure of the synthetic VCT or resilient tile.  Due to their very small size they have the ability to move around and work their way to the surface.  Upon reaching the surface they are exposed to light and air; typically they will either vaporize or fade becoming unnoticed to the casual observer.  However, if they are kept from exposure to light or air, they turn yellow with age.  Evidence of this explanation can be seen in supermarket and large department stores where yellowed areas can be seen on the VCT floor where display counters and checkout lines have been moved.  

Once a floor becomes yellowed it can be difficult to remove the yellowing.  Depending on the type of floor, it may be possible to reduce or remove the yellowing by cleaning and waxing hard surface floors or having carpeted floors professionally cleaned.

In most instances where mats are placed on floors and discoloration results, the customer is faced with a difficult decision: Use no mat so the floor doesn’t discolor, however, the floor is damaged by tracked-in soil, moisture and dirt, and the entire area deteriorates. Or use a mat and protect the floor with resulting discoloration in the area underneath the mat.  Of the two, most customers select the latter.

Corrective Action

Discoloration can usually be removed by stripping and re-waxing.  In the case of carpet, professional carpet cleaning is usually required.