We get them here also, any light or sun on white wall and they just all group up, box elders also but they are noticeably different as I get those (also attracted to white/light)
They aren't real lady bugs; I always called them japanese beetles; I have 1500 ladybugs I purchased in basement (remove aphids as I grow dandelions and other food for my tortoise during Winter) never was bitten by a ladybug but the fake ones have hit me on a few times. they wreck vacuums with the smell they "spit" so don't do that.
I will look more closely next time i see a mess. Yes, they accumulate most on the outbuilding most exposed to the sun. It has light grey paint. I don't see them on the north side of the bldg.
Japanese beetles are, of course, still another very different species.