Carpeting, like most other textiles, is made under tension. Tension is necessary so that the loom will function properly, producing a carpet uniform from one portion to the next. Yet carpeting differs from most textiles in that the backing may be composed of several layers, which are not generally preshrunk. When backing yarns absorb moisture the fibers swell, resulting in the relaxation of the yarns previously held under tension. Moisture, which produces swelling may result from humidity, spills or cleaning.

If two adjacent areas of a carpet are not manufactured under the same amount of tension, unevenness or tippling can develop. This will also occur if the tension of the second carpet backing is not uniform with the primary backing.

Each case of rippling is different. The ripples may extend across the entire width of the carpet; from the edge to the middle; in the middle only; along the edges, or in one small section.

This situation can sometimes be corrected by wetting the backing and tacking the rug out in a stretched position. Now ever the ripples may recur when moisture is again present.

Ripples can also be caused by dragging heavy furniture across the carpet or by sliding and pulling of carpet in traffic areas caused by walking.
Improper carpet installation may also cause ripples. If installation over padding is not done by power stretching, the carpet will still have some capacity to stretch. It will likely stretch in heavy traffic areas, and this may result in buckling which is a form of rippling. In this case the carpet must be re-stretched and reinstalled.