Having wall-to-wall carpeting offers distinct benefits, but sometimes walking on it can become hazardous and its appearance can deteriorate due to buckling or rippling. The reasons for ripples across the floor can range from improper installation to excess humidity to long term wear.
To understand why ripples happen, it is good to understand how carpets are fabricated. Most residential carpet is manufactured by inserting yarn into a backing material to form the face material. The yarn/face material and primary backing is then back coated with a synthetic latex adhesive to lock the fibers in place. Finally, a secondary backing is applied to provide dimensional stability. (See diagram).
Improper installation methods almost always guarantee carpet rippling and can range from the installer not using a power stretcher or only power stretching in one direction. Also, padding with improper thickness or density for the carpet can also cause rippling. Therefore, make sure to purchase the proper carpet pad for your carpet and to use a qualified carpet layer for installation.
Excessive water from humidity or improper steam cleaning can break down the latex adhesive and cause rippling. Stretching the carpet can help the appearance but the carpet has probably been damaged and buckling will more than likely return. Replacement might be your best option.
Finally, buckling occurs overtime because the carpet stretches due to regular foot traffic and wear. Every carpet reaches an age when it must be replaced because the secondary backing and latex start to breakdown. Stretching the carpet can remove the ripples but these areas will still be prone to buckling. Replacement might be your best option.