Minecraft wiki entry for Iron_Golem, associated text: To find a valid spawn point, up to 10 attempts are made to spawn a golem within a 16×13×16 box centered on the villager (villager block position +7/−8 blocks along x/z axes and ±6 blocks along y axis). A random y column is picked and then the topmost block in that column is selected that is air, water, or lava, and has a "solid-blocking" block underneath, or the block at y=+6 if none such is available in that column. The target location is then checked whether the block underneath has a solid top surface (which is not the same as "solid-blocking"). The target block and 2 blocks above must not be a full block, nor be redstone-powered, nor be rails, and the two blocks above must not be water. This means the iron golem can spawn inside 1-deep water or inside blocks like slabs, fences, and carpets (if other checks pass). Adjacent blocks are irrelevant, so golems can spawn partially inside adjacent solid blocks.[1] However, the spawning iron golem still must not collide with any existing entities.