From time to time customers complain that mats cause the floors beneath them to discolour. This complaint has applied both to carpet and hard surface floors such as vinyl or tile. The discolouration is usually a yellow or brown colour. The most likely cause for this is moisture. There are several potential ways that moisture can cause discolouration.

1. Moisture from the ground comes 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 evaporation, therefore trapping the moisture, thus causing the discolouration. This seems to be most common at entrances where cold or warm air enters buildings when the door is opened causing condensation (sweating).

2. Placement of mats on freshly cleaned and still damp carpet. This prevents carpet from fully drying, thereby causing discoloration.

3. Moisture from the back of mats. If not properly dried, the back of mats can be damp, thereby providing moisture to cause discolouration.

4. There can be a reaction between chemicals in the rubber backing and the floors or floor finishes used on hard surface floors.

5. Lack of exposure to sunlight. It is common to see floors change colour when they are covered by counters, file cabinets, etc. This is caused by both lack of exposure to sunlight and restricted airflow.

In most instances where mats are placed and floor discolouration results, the customer is faced with a difficult decision. Use no mat and the floor doesn't discolour, 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 discolouration in the area underneath the mat. Of the two, most customers select the latter.

Corrective actions

Discolouration can usually be removed by stripping and rewaxing. In the case of carpet, professional carpet cleaning is usually required.