Every Phase 1 LA-area city's home addition cost page, in one place, sorted by cost-tier.
Single-room or primary-suite addition, 300–500 sqft, slab-on-grade single-story, standard finishes.
California typical range (2026): $165,000–$310,000 standard tier across LA-area cities (two-story or with foundation underpinning adds 35–50%).
What anchors the schedule: Always plan-check (no OTC path).
Setback constraints, FAR caps, and Title 24 whole-house compliance triggers drive the schedule.
Home Addition cost, Home Addition cost Los Angeles, Home Addition cost California, Home Addition permit, TRUbee project hub, construction cost comparison.