Need Help, Mob Grinder For Minecraft Is Not Working.

[hauteur32]

My mob grinder is at Y= 138 and ground level is at Y= 63. Light level is zero inside. But no mobs are spawning. Also the spawning platforms are made of cobble and are not half slabs. Did I not go high enough?

[76561198152167391]

Try using stone instead of cobble. You can make them using the furnance. Cobblestone then put coal.

[filler text]

Post in that Minecraft group. This post isn't off topic enough.

[hauteur32]

I can try, but the spawning surface doesn't matter unless it is a transparent or half block

[shoopy]

You're probably better off just getting Minefactory Reloaded and using the spawners.

Or even Ender IO powered spawners.

[hauteur32]

Im not using any mods, Im doing a vanilla survival.