What Causes Carpet to Buckle or Ripple?

Full article with thanks to https://www.thespruce.com/what-causes-carpet-to-buckle-2908830

You may have seen, or experienced in your own home, wall-to-wall broadloom that has ripples in it. The carpet is loose in the affected areas and seems to have waves or wrinkles in it, rising from the surface. This is known as buckling and may be referred to as wrinkling or stretching. There are several reasons why broadloom may buckle.

• Humidity and Carpet Rippling
  
  Humidity is one of the biggest culprits of carpet buckling. It is especially common in four-season climates during the summer, because there is such a drastic change in the conditions from the cooler months. In highly humid climates, the moisture in the air penetrates the carpet and causes it to swell.In non-severe cases where the carpet has buckled due to high humidity, the carpet may lay flat again, without any intervention, once the moisture levels in the air return to “normal”—whatever the “normal” is for that area. However, in cases where the carpet is severely buckled, it may be necessary to take action to remove all of the ripples (see below).To reduce the likelihood of your carpet buckling in humid conditions, run your air conditioning during the summer months. Or, you may run a dehumidifier in the area, which draws moisture out of the air (and thus out of your carpet).
  
• Dragging Heavy Items
  
  Another common reason that carpet may buckle is the dragging of heavy furniture (or similar item) across the surface of the carpet. When a heavy item is dragged across the surface, it tugs on the carpet and can cause the carpet to stretch.To avoid causing your carpet to buckle when moving furniture or other heavy items, you must take precautions. It is best to lift the item and carry it if it is possible.If the item is too heavy to be completely lifted off the carpet, then use two sheets of sturdy plywood to move it. Place one sheet on the carpet and “walk” the item onto the plywood (move it slowly, one side at a time, almost as if it was walking forward). Then place the second plywood sheet on the carpet in front of the first, and “walk” the item from the first onto the second. Once you have the item completely on the second sheet, lift the first sheet and place it in front of the second, and continue in this manner until the item has been relocated.
  
• Improper Installation of the Carpet
  
  Carpet buckling may occur as a result of poor installation of the carpet. When a wall-to-wall carpet is installed, it must be stretched tightly and then is secured in place with tack strips along the edges of the carpet. If the installer has not stretched the carpet tightly enough, it may loosen slightly, which could cause it to ripple. Ideally, carpet should be stretched during the installation using a power stretcher, which will reduce the chances of buckling.If the carpet is being installed in an area in which the conditions are significantly different than where it was previously stored (for example, from an unheated warehouse to a heated home), then the carpet should be allowed to acclimate before installation. This should reduce the possibility of buckling. 
  
• Incorrect Underpad
  
  If an improper cushion is used under the carpet, it could cause the carpet to buckle. This would occur if the pad was not dense enough to adequately support the carpet, and allowed too much flexibility in the carpet.To prevent this issue, the correct underpad must be used under the carpet.
  
• Delamination
  
  Broadloom has a primary backing, which is what the fibers are fastened to, and a secondary backing, which holds everything together and is what you see when you look at that back of the carpet. Delamination occurs when the secondary backing detaches from the primary backing, due to a breakdown of the latex adhesive. When this occurs, the top of the carpet is free to move and can buckle.Delamination can occur as a result of wet carpet (see below) or a manufacturing defect. If you suspect that the carpet is defective, contact your retailer or carpet manufacturer, who will likely send an inspector to look at the issue.
  
• Wet Carpet and Ripples
  
  Just as too much moisture in the air can cause a carpet to buckle, so can too much moisture in the carpet itself. Carpet that has become overly wet, as the result of flooding or improper steam cleaning, is extremely susceptible to stretching. Because of the risk associated with over wetting, it is advisable to have your carpets professionally cleaned, rather than doing it yourself with a rented machine.

• My Carpet Buckled—Now What?
  
  If your carpet has buckled, it needs to be re-stretched. It is best not to leave it too long, because the ripples could become more severe over time, and could cause the carpet to crease.Once the carpet creases (i.e., the ripple becomes so prominent that the carpet is folded sharply at the peak) it is too late to be fixed. Sure, you can still get the ripples out, but the crease in the carpet will likely never come out, and even laid flat will still look buckled.To re-stretch your carpet, you could contact your retailer and have their professional installers come out to take care of it. Unless the carpet is less than a year old, it will likely cost you anywhere from $100 and up, depending on the severity of the ripples, and any other work that needs to take place (moving furniture, opening nearby seams and re-seaming, etc.).

Full article with thanks to https://www.thespruce.com/what-causes-carpet-to-buckle-2908830