body, html {
  height: 100%;
  margin: 0;
}

.wrapper {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 20px;
  grid-template-rows: 50px 1fr 50px;
  grid-template-areas:
    "header header header header"
    "main main . sidebar"
    "footer footer footer footer";
  height: calc(100% - 2em);
  padding: 1em;
}

header {
  background-color: yellow;
  grid-area: header;
}

#text {
  background-color: limegreen;
  /*height: 500px; /*seems to reduce the height of the green box so that there's a blank space at the bottom once this is enabled*/
  grid-area: main;
}

#sidebar {
  background-color: hotpink;
  grid-area: sidebar;
}

footer {
  background-color: cyan;
  grid-area: footer;
}