I love this door brace. It is simple, easy to install, and you can purchase several of them for back ups in the event you have to move between locations.
You need to make sure you have a high quality door mounted through the door frame and into the studs behind it. (If your not sure, take out two screws from each hinge and use a four to five inch screw in its place. This will make sure your hitting the framing of the house behind the door frame.)
With a decent door and this in place, not only will the undead horde not be able to push through your doorway, but neither will looters or your mother in law.
(Legal disclaimer – before doing any work make sure you are fit and able to do it. If you have any questions, hire a professional. – Thanks Mr. Lawyer for making me put in a disclaimer)