How to add a simple 8dp header/footer to Android's RecyclerView?

Adding a top padding and setting clipToPadding to false will do the trick.
Something like this:

  <android.support.v7.widget.RecyclerView
    android:id="@+id/recyclerview"
    android:paddingTop="8dp"
    android:clipToPadding="false"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

If you are using a RecyclerView with a layout_weight, and paddingBottom is not working for you, making sure you set the layout_height to 0dp! Otherwise, strangely, paddingTop works but paddingBottom does not:

<android.support.v7.widget.RecyclerView android:id="@+id/recycler"
    android:paddingBottom="20dp"
    android:clipToPadding="false"
    android:layout_weight="1"
    android:layout_width="match_parent"
    android:layout_height="0dp" />