Rolling wheels or casters of any type or size (from desk chairs to wheelchairs) over carpeting produces a rippling effect in the carpet backing. In time, repeating this practice will cause the backing to separate, ruining the carpeting. Additionally the wheels of the chair will pack down the carpet fibers and eventually flatten the area permanently. Once flattened it’s simply a matter of time before this area is worn through by the wheels. When wheels are unavoidable, the carpeting should be not be installed over pad but glued directly to the sub-floor. Doing so will not prevent the above damage but simply slow down the process.
Of course, with desk chairs, the problem can be eliminated by simply placing a desk-chair pad between the chair and the carpeting but this option is not without a downside.
The downside of chair mats are;
(1)carpeting under the pad will not fade or wear with the rest of the room.
(2)edges of the pad will attract soil due to mild static charge.
(3)statically charged soils will eventually bond to the carpet fibers.
(4)soil contaminated air will stain the carpet (along pad edges) as air passes throughout the room.
Weekly vacuuming along the chair pad edges will help to lessen any permanent build up of soils.