What Causes Yellowing of Tile Under Mats?

From time to time we are asked about mats causing the floors beneath them to discolor. This is common for both carpet and hard surface floors such as vinyl or tile. The discoloration is usually a brown or yellow color. The most likely cause for this is moisture. There are several potential ways that moisture can cause discoloration.

  • Lack of exposure to sunlight and/or restricted air flow. It is common to see floors change color when they are covered by anything, whether it be a mat, or a counter, a file cabinet, etc.
  • Placement of mats on freshly cleaned and still damp carpet. This prevents carpet from drying, thereby causing discoloration.
  • Moisture comes from the ground up through the floor until it reaches the floor surface. This moisture normally evaporates and goes unnoticed. Placement of a mat on the floor prevents the normal evaporation and traps moisture, thus causing the discoloration. This seems to be most common at building or home entrances where cold or warm air enters buildings when the door is opened causing condensation (sweating).
  • Moisture from the back of mats. If mats are not properly dried, the damp mat can provide moisture to cause discoloration.
  • Chemical reaction between the chemicals in the rubber backing and the floors or floor finishes used on hard surface floors can cause discoloration.
  • In most instances where mats are placed and floor discoloration results, the customer is faced with a difficult decision. Use no mat and the floor doesn't discolor, however, the floor is damaged by tracked in soils, 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 actions. Discoloration can usually be removed by stripping the floor and rewaxing. In the case of carpet, professional carpet cleaning can usually remove the staining.


Rightway, Inc.
2800 Regal Road
Suite 104
Plano, TX 75075
Tel: 1-800-637-0938
Fax: 972-867-1936