In case anyone doesn't know it, if you dig a hole or trench 1m deep and put spikes in it so they are flush with the ground, the zombies will path right over then as if they weren't there instead of going around, causing them to take damage. Also, zombies love to cut corners, so will walk right through spikes at the corners of your base if they are trying to go around the corner. Works very well.
Of course, I normally don't bother and just rub outside to kill them as soon as I hear them. Sprinting up to them and I can usually kill them with my spear before they scream. They die very easily.