Casita and ADU construction in Las Vegas typically takes 6 to 14 months from initial consultation to keys, broken into three phases: planning and design (1 to 3 months), permitting and approvals (2 to 6 months), and construction (4 to 9 months). Garage conversion ADUs can be completed faster because they reuse existing structure. Detached custom casitas take the longest due to foundation work and standalone utility connections.