background of div not obeying z-index property

Question

I have a div wrapper and a div row and both have position properties set to relative. The wrapper div has a higher z-index than the inner div and both have background's set, however, the higher z-index background is still below the lower div's background. JS Fiddle Example

.wrapper {
  position: relative;
  z-index: 1000;
  border: 1px solid black;
  width: 131px;
  height: 25px;
  background: repeating-linear-gradient( to right, rgba(255, 0, 0, 0), rgba(255, 0, 0, 0) 10px, black 11px, black 1px);
}

.row {
  position: relative;
  z-index: -1;
  margin-top: 2px;
  margin-bottom: 1px;
  width: 100%;
  height: 20px;
  background: linear-gradient( to right, rgba(255, 0, 0, 0) 50%, red 50%);
}

<div class="wrapper">
  <div class="row"></div>
</div>

Answer 1

If you want the grid lines over the red bar, remove the z-index from the wrapper div:

.wrapper {
  position: relative;
  border: 1px solid black;
  width: 131px;
  height: 25px;
  background: repeating-linear-gradient( to right, rgba(255, 0, 0, 0), rgba(255, 0, 0, 0) 10px, black 11px, black 1px);
}

.row {
  position: relative;
  z-index: -1;
  margin-top: 2px;
  margin-bottom: 1px;
  width: 100%;
  height: 20px;
  background: linear-gradient( to right, rgba(255, 0, 0, 0) 50%, red 50%);
}

<div class="wrapper">
  <div class="row"></div>
</div>