Which horror films get the look of real property decay spot on?

We work in the damp and timber treatment industry, so we spend our days dealing with things like rising damp, dry rot, crumbling timber, and mould-covered walls. It's become a bit of a running joke in our team that half the horror films we watch feel like walking into one of our survey appointments.

Films like Crimson Peak and The Conjuring do a genuinely brilliant job of recreating what real property decay looks like. The tide marks on walls from rising damp, the soft and crumbling timber from rot, even the black mould patches; it's all remarkably accurate in some of these productions.

We've always wondered whether production designers actually research real damp and timber conditions or whether they just find derelict properties and film in them. Either way, the results are often spot on.

What are your favourite films where the setting feels genuinely decayed and not just a bit of paint and cobwebs thrown on a clean set? Always looking for recommendations; purely for research purposes, of course.