Endermen are dismantling my mob grinder.

This question has an answer that suggests endermen can't spawn on slabs, so if I cover the whole floor with slabs, I should be fine. Except I read single slabs are considered "transparent" and monsters can only spawn on "opaque". OTOH, double slabs are considered "opaque"... how does that relate to monster spawning?

  • 1
    For your second question, you should submit a second question. However, endermen and blocks has already been covered here and here, so you don't need to. (I've edited out the second question.) May 16, 2013 at 19:40

4 Answers 4


Mobs cannot spawn on normal, right-side-up single slabs (the ones occupying the lower half of the block), as they're considered transparent blocks. They can spawn on upside-down single slabs (as of the 1.5 update) and double-slabs (which are full, opaque blocks).

Flooring your grinder with regular half-slabs will prevent all mobs from spawning, not just endermen.

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    This is incorrect. Upside-down slabs are valid for spawning; this was introduced in the same update that allowed redstone to be placed on upside-down slabs.
    – Kevin Reid
    May 17, 2013 at 2:02
  • @KevinReid Ah! Yes, my info is out of date. Funnily, the first version I wrote here was correct then! I'll revert to that. May 17, 2013 at 2:46
  • Flooring the grinder with double slabs will prevent it from being dismantled. Flooring the OUTSIDE of the grinder with right-side-up slabs will force all mobs to spawn inside only.
    – SF.
    Jul 20, 2013 at 8:41

No, mobs cannot spawn on single slabs. This wiki article explains in detail the requirements for any given mob to spawn.

To prevent endermen from making holes in your grinder, make the spawning level only 2 blocks high, or set mobGriefing to false.

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    I like to make my grinders/farms 2.5 high (half block on top). Prevent Endermen from spawning, and give those poor buggers a little breathing room. We're already subjecting them to genocide, no need to be cruel about it. May 16, 2013 at 19:47
  • or make the grinder out of stuff that the endermen can't move (cobblestone is enough) May 16, 2013 at 20:51
  • @ratchetfreak Endermen can move cobblestone May 16, 2013 at 21:01
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    @mikeTheLiar no they can't May 16, 2013 at 21:02
  • @ratchetfreak hmm. Looks like that answer needs to be updated.... May 16, 2013 at 21:06

If you have a diamond pickaxe, rebuild your Mob grinder 2 blocks high and out of obsidian. (pretty sure enderman cannot move this)


Mobs can spawn on slabs. I played skyblock on hardcore and thought they couldnt spawn on my bridge but no.There was a spider right there and it knocked me out of the world. (btw was playing on java).

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