小编Lev*_*ray的帖子

html,
body {
  height: 100%;
}
.site-main {
  height: calc(100% - 72px);
  display: flex;
}
.site-main > div {
  min-width: 85%;
  height: 100%;
}
.site-main > aside {
  min-width: 15%;
  height: 100%;
  background-color: $darkest-blue-grey;
}

<header>
  <h1>Title</h1>
</header>
<div class="site-main">
  <div></div>
  <aside></aside>
</div>