In any "outdoor" environment (ie you don't enter through a load screen), rain falls indoors, regardless of what kind of roof is above you. You can be standing on the bottom floor of a ten-story concrete building, but you still get rained on just as much as if you were outside. The floor, the characters, your placed objects all still get wet. This has kinda bugged me for years. It would be extremely cool if there were a mod that kept the interior of buildings dry when it rains. Or even had varying levels of rain protection based on roof type. A lot of the shack roofs and pre-existing buildings are kind of janky and full of holes, so it would make sense for those to be less effective. If your standard "shack roof" were a bit leaky but a concrete roof kept you perfectly dry, that would be even more cool. Not sure if a mod for this already exists, but if so I haven't been able to find it.