ADU Construction Checklist for San Diego Homeowners

An accessory dwelling unit (ADU) is a self-contained living space on the same lot as a single-family home — its own kitchen, bathroom, and entrance. Choosing the type is the first decision, because it shapes the budget, the timeline, and what your lot will allow.

Before falling in love with a design, confirm your property can actually accommodate it. Feasibility is about the realities of your specific lot, and a contractor or designer can assess these quickly.

California has actively encouraged ADUs through state law, and local rules in San Diego work within that framework. Requirements cover things like maximum size, height, setbacks, owner-occupancy, and parking, and they have changed repeatedly in recent years as the state has worked to ease housing supply.

Because these rules genuinely do shift, the right move is to confirm the current requirements for your address rather than rely on what was true a year or two ago. A design-build team that does ADUs regularly will know the current state of the rules and design to them from the start.

An ADU is most valuable when it feels intentional rather than tacked on. Designing it to complement the main home — matching rooflines, materials, and proportions — protects both the look of your property and its long-term value.

Inside, design for the unit's purpose. A rental benefits from durable finishes and an efficient, private layout; a space for aging parents benefits from accessibility and single-level living; a home office or studio has its own light and storage needs. Thinking through the end use up front leads to a unit that serves its purpose for years and adds real value to the property.

ADUs require permits, and the process involves design, plan submittal, review, and inspections — similar in structure to other construction, with ADU-specific considerations layered in. Each step is a fixed point in the timeline, so they belong in the plan from the start.

A design-build approach is especially well-suited to ADUs because design and construction live under one team. That means the design is grounded in what's actually buildable and permittable on your lot, the budget and the drawings are reconciled as you go, and one point of accountability carries the project from feasibility through final inspection — instead of you coordinating between a separate designer, permit expediter, and builder.

ADU budgets vary widely by type, size, finish level, and site conditions — a garage conversion and a large detached new-build sit far apart. Rather than a flat figure that won't match your project, the useful step is to scope your specific ADU: type, size, intended use, and what your lot requires. The project range estimator gives a planning band, and a free on-site consultation produces a written range you can budget against.

On financing, homeowners commonly fund ADUs through home equity, renovation loans, cash, or ADU-specific financing programs. Terms and program availability change, so confirm current options with a lender before counting on any specific figure or program.

Most homeowners build an ADU for one of a few reasons, and naming yours sharpens every other decision — type, design, and budget all follow from the goal.