Two of the most popular ADU paths in San Diego are converting an existing garage and building a brand-new detached unit. Both are excellent options, but they suit very different lots, budgets, and goals. Here is how we help homeowners decide.
The case for a garage conversion
Converting an existing garage is usually the faster, lower-cost path. You are reusing a foundation, a roof, and walls that already exist, which means less demolition, less new structure, and often fewer site complications. For homeowners whose main constraint is budget, a conversion frequently delivers the strongest return per dollar. The trade-offs are a fixed footprint, existing ceiling heights to work within, and the loss of covered parking.
The case for a detached ADU
A detached unit gives you a blank canvas. You can optimize the floor plan for light and privacy, size it closer to the maximum your lot allows, and keep it fully separate from the main house, which tenants and family members both tend to value. You also keep your garage. The trade-off is cost and complexity: a detached ADU needs its own foundation, grading, and utility runs, and it involves more site coordination.
What your lot is telling you
The right answer is often written into the property itself. Setbacks, lot size, slope, the position of existing structures, and how far utilities have to reach all shape what is practical. A flat lot with a detached garage near the alley behaves very differently from a tight hillside parcel with limited access. Before committing to either path, it is worth a feasibility look that tests both options against your actual dimensions.
Rental and resale considerations
A detached unit with its own entrance and a bit of outdoor space often commands stronger rent and broader resale appeal. A conversion, on the other hand, can be the smarter return when budget is the binding constraint and the existing garage is well positioned. Neither is universally better. It depends on what you are optimizing for.
How to decide
Start with your goals and budget, then pressure-test them against the lot. We often run a quick feasibility study that compares both approaches on your specific property, so the decision is grounded in real setbacks and real costs rather than assumptions.
Converting a garage removes covered parking, so confirm your parking obligations early. Many San Diego properties near transit or with existing parking are exempt from replacement requirements, but it is worth verifying before you plan.