Minecraft wiki entry for Roof_types, associated text: Some mansard roofs resemble bonnet roofs, having a shallow lower pitch which extends beyond the curtain walls. The key features of a mansard roof are its squarish profile and its increased volume of roof space compared to a gable roof and other simpler designs. Note also that as the main point of a mansard roof is to make the roof volume usable, it will almost certainly have dormers built in to it to provide lighting.