Learn when the best time for ADU construction is based on weather, permits, contractor availability, and rental market timing to build smarter and avoid delays.

If you’re a homeowner in San Diego planning to build an ADU, understanding the city’s permit process is crucial. Getting an ADU permit isn’t just a matter of paperwork and stamps — it’s a detailed, multi-step process involving prescreens, department reviews, and rechecks before you’re cleared to start construction.

The short answer is: it depends. Costs can vary widely depending on size, design, location, and construction method. Below, we’ll break down the main cost factors, explore differences between detached, attached, conversion, and prefab ADUs, and walk through a real-world example to give you a realistic picture.