Many times carpet loosens causing bumps or ripples in your carpet. This may be caused by a few different reasons. One would be bad installation, two dragging heavy furniture, three high heat over time or high humidity or temp change and last just good old age of carpet as carpet has tendency to stretch over time. Here are some other facts from the Carpet and Rug Institute CRI. Here are some before and after pictures of carpet that San Diego Carpet Repair Power Stretched or Correctly called Power Re-Stretched today in Carmel Valley!