I made an attic and all was well except two things
This next picture was actually taken prior to the other one and shows part of one problem, which is that placed objects can be clipping through rooves. They can go much farther through.
the other problem is that Hearthlings will walk right through your roof if there is an attic for them to walk on and a ladder for them to get up on.
I didn’t have a picture of it but at one point I caught my Hearthlings getting up in the morning and walking through the roof and down the ladder to get out of the house.