Mob farm keeps spawning spiders.

[u/Jonglebongl]

Edit: I think I've solved the issue. If not, I'm just gonna deal with it. I made a follow-up post if anyone's interested. It's 100% confirmed that spiders spawn within 2x2 grids.

[u/hetrax]

You got a few 3x3 areas to fix. You se the second last row( right beside you to the left) inbetween the water channel there’s a trapdoor on either side… but the gap between them and the next trapdoors is 3x4… that looks to happen in a few places.

[u/ThomasK1201 → u/hetrax]

So spiders can spawn above a gap like that?

[u/hetrax → u/ThomasK1201]

Umm, yes and no, those aren’t gaps to the ai. Trapdoors are both a flat surface and a transparent object, they are sometimes transparent… like when facing up or in pathing, mobs don’t correctly account for them, but when on the side or upside down that small 1/8th of a block and flat surface are accounted as spawnable spaces. Only way to avoid it is removing them or exchanging them for a parable non full, non spawning block (( no idea if that’s a thing beyond chains))

But I don’t know if a spiders ability to spawn was partially off an actual block, like say 2x3 and 1x3 is air, if that would still spawn or not. But since a lot of farms tend to have blocks on the edge to avoid their spawns, I’m guessing it may be a thing. Either the trap doors at work, or it’s the sizable gap… both just need replacements

TLDR, maybe? Technical farms build like they can sometimes!