i think it'd be neat if, in project zomboid, you could use tier 3 wooden walls to make a sort of "mold" and then fill it in with concrete to make concrete "walls" that are a full tile thick, block noise, and zombies can't even path through or attempt to break down
expensive to make but essentially impenetrable if you can make enough of them
maybe you could also encase stuff inside. like if you've got a corridor full of zombies you've sealed off everywhere but the top? seal the bastards in concrete if you've got enough of it
obviously you'd be able to break it with like, explosives and maybe mining tools (pickaxe comes to mind) but it's the perfect way to keep zeds out of your compound
... maybe some of the pre-apocalypse places that make sense for it could have these extra chonky concrete walls as well
like the prison, and maybe some military bases whenever the map gets expanded towards fort knox