ADU basics

New to ADUs? Start here.

Everything a San Diego homeowner should know before their first conversation with a builder, in plain English.

What counts as an ADU

An accessory dwelling unit is a complete, self-contained home on the same lot as your main house: its own entrance, kitchen, bathroom, and living space. California law requires cities to allow them on most residential lots, which is why ADUs went from rare to everywhere in a few years.

The three ways to build one

Detached: a standalone backyard home, maximum privacy and rental appeal. Attached: an addition with its own entrance, often the budget-friendly path. Garage conversion: turn structure you already own into living space, frequently the fastest permit.

What drives the cost

Size, site conditions, and finishes. Utility connections matter more than most people expect: sewer, water, and electrical routing can swing a budget. That's why we check feasibility before you spend anything on design.

Why the city matters so much

Setbacks, height limits, maximum size, and parking rules all change at the city line. The same backyard could fit a two-story ADU in one city and a one-story in the next. Check your city's guide before you fall in love with a floor plan.