Why did some Pueblo peoples build multistoried flat-roofed homes?

Pueblo peoples and their ancestors, the Ancestral Pueblo, built multistoried, flat-roofed homes for several functional and defensive reasons:

• Defensive Security: By constructing buildings without ground-level doors or windows, the structures presented a solid outer wall that was difficult to breach. Residents traditionally entered ground-floor rooms through rooftop openings using ladders, which could be easily removed in the event of an attack.12
• Efficient Use of Space: The "stepped" design, where each successive story was set back from the one below, created terraces on each level. These terraces provided valuable outdoor living space, which was heavily utilized by the community.123
• Structural Utility: The flat roofs were engineered to support significant weight, constructed with heavy crossbeams covered by poles, brush, and a thick layer of adobe. This design allowed the roof of one level to serve as a terrace or floor for the level above.321
• Storage and Organization: Ground-floor rooms were often used exclusively for storage, particularly for grain, keeping essential supplies secure and accessible through the roof.1