Hot to add a wrapper to all classes with class="flex_column

Hi,
I need to wrap all DOM items with class=”flex_column” to add background-zoom feature to Enfold: http://www.tipue.com/blog/css-background-zoom/
Any idea how to do that? For example some code for functions.php?

By default Enfold creates the DOM like that:

<div class="flex_column_table">
   <div class="flex_column"></div> <== hat set background-image with backend editor.
   <div class="flex_column"></div> <== hat set background-image with backend editor.
   <div class="flex_column"><div> <== hat set background-image with backend editor.
</div>

What I need is this:

<div class="flex_column_table">
   <div class="outer">   
      <div class="flex_column"></div> <== hat set background-image with backend editor.
  </div>
   <div class="outer">   
      <div class="flex_column"></div> <== hat set background-image with backend editor.
  </div>
   <div class="outer">   
      <div class="flex_column"></div> <== hat set background-image with backend editor.
  </div>
</div>