Residential construction increasingly includes accessory dwelling units (ADUs) as homeowners seek flexible, cost-effective ways to add living space, generate rental income, and increase property value without undertaking large-scale renovations; ADUs—ranging from detached backyard cottages to garage conversions and interior apartments—require careful coordination of site planning, structural design, permitting, and utility hookups to meet local codes and neighborhood considerations, and successful projects balance efficient construction methods, durable materials, and thoughtful design to ensure privacy, accessibility, and long-term durability while maximizing usable square footage and return on investment.