You can use this module with the following in your ~/.xmonad/xmonad.hs:

 import XMonad.Layout.Master

and add something like

 mastered (1/100) (1/2) $ Grid

to your layouts. This will use the left half of your screen for a master window and let Grid manage the right half.

For more detailed instructions on editing the layoutHook see XMonad.Doc.Extending#Editing_the_layout_hook.

Like Tall, Master supports the Shrink and Expand messages.