Minecraft wiki entry for Tips_and_tricks, associated text: The simplest solution is to use a fence gate instead of a door, as zombies do not recognize them as doors. One must, however, guard against creepers, which will treat fence gates as fences as per priming-time detection range mechanics (creepers will start the countdown even if blocked by fences, as they are in the same space as the fence). The laziest way to protect against undead intruders is to dig a 1×3 trench in front of the door—to break down doors, zombies must destroy the top half of the door. If zombies are on the door trench, they must jump to attempt to break the top half of the door, which resets the zombie door breaking mechanic. Note that this method only works if the door was installed flush to the outside wall of the dwelling. Also, putting a block underneath the door forces the zombies to jump, break, fall, fail, repeat, exact same mechanic, simply make a 3 high doorway and instead of a door and another block on top, put a block on the bottom and door on the top two block spaces, allowing villagers to still use these doors.