San Diego ADU Construction: Detached, Garage Conversion & JADU

An accessory dwelling unit, or ADU, is one of the smartest ways to add real value and usable living space to a San Diego property. Whether you want rental income, a private space for aging parents, a home office that is finally out of the main house, or a guest suite for grown kids, an ADU gives you a fully independent home on the lot you already own. We have built and remodeled across San Diego County since 2014, and we handle ADU projects as one accountable package, from the first site check through final inspection. Here is what you need to know before you start.

The Four Types of ADUs

California recognizes four basic kinds of accessory dwelling units. Each one suits a different lot, budget, and goal, and choosing the right type up front is the single biggest decision in the project.

Detached ADU

A detached ADU is a standalone structure built in your yard, fully separate from the main house. This is the premium option and the one most people picture when they think of a backyard unit. It offers the most privacy and the highest rental appeal because tenants get their own building, their own entrance, and their own outdoor space. Detached units run up to 1,200 square feet under state rules and work best on lots with the room to support new construction. They cost the most because you are building a complete new structure from the foundation up, but they also add the most value and flexibility.

Attached ADU

An attached ADU shares at least one wall with your existing home but functions as a separate residence with its own private entrance, kitchen, and bathroom. It suits homeowners who want a true second unit without giving up as much yard as a detached build, and it can be a cost-effective middle path because it borrows structure and utility runs from the main house. Attached units are a strong fit for multigenerational living, where you want family close but independent.

Garage Conversion ADU

A garage conversion turns an existing garage into a complete living unit. Because the walls, roof, and slab already exist, this is usually the most affordable route to a full ADU, and it leaves your yard untouched. The trade-off is that you give up covered parking and you inherit the footprint and ceiling height of the original garage. For homeowners who rarely park inside or who have driveway space to spare, a garage conversion is often the fastest, lowest-cost way to add a rentable unit. We address the realities of conversions head on, including raising the slab, adding proper insulation, upgrading the electrical panel, and meeting current energy code.

Junior ADU (JADU)

A junior ADU is a compact unit of up to 500 square feet carved out of the existing footprint of your single-family home, often a converted bedroom or attached garage area. A JADU can have an efficiency kitchen and may share a bathroom with the main house, which keeps the build simpler and cheaper. The key rule to know is that a JADU carries an owner-occupancy requirement, meaning you must live in either the main house or the JADU itself. It suits homeowners who want a modest income unit or a self-contained in-law space without adding new square footage to the property.

Why San Diego Is a Strong ADU Market

California has spent the last several years rewriting its statewide ADU laws to make these units far easier to build, streamlining approvals, limiting how much cities can restrict them, and pausing owner-occupancy requirements for standard ADUs. The result is that on a typical single-family lot you can generally add one ADU plus one junior ADU, and in many cases stack more than one unit. The City of San Diego has been especially ADU-friendly and has offered programs allowing additional units in exchange for affordability commitments, though the local rules continue to evolve, so we always confirm current allowances for your specific parcel before design begins.

San Diego is a natural fit for this kind of building. Housing demand is high and rents are strong, so a well-built unit can generate meaningful monthly income or offset a mortgage. Many local lots, especially in inland communities like Poway, Santee, El Cajon, and Escondido, have the room to support a detached unit, while tighter coastal and urban lots are often well suited to attached units, garage conversions, or a junior ADU. And with the cost of housing here, families increasingly want a way to keep aging parents or adult children close without buying a second property. An ADU answers all three needs at once, which is why we see steady demand for them across the county.

It is worth knowing that the rules around how many units a lot can support, and whether incentive or bonus programs apply, continue to shift at both the state and city level. We track those changes so you do not have to. Before we draw a single line, we confirm exactly what your parcel allows today, which protects you from designing around an allowance that has already changed.

How the ADU Process Works

A successful ADU follows a clear sequence, and we manage every step so you are not coordinating separate trades on your own.

• Feasibility and site check. We walk the property, confirm what your lot and zoning allow, locate utilities and easements, and identify setbacks. This is where we tell you honestly which ADU type makes sense for your space and budget.
• Design. We develop a floor plan and layout that fits the site, your goals, and your finish preferences, balancing livability against cost.
• Structural engineering. New construction and conversions both need engineered plans for foundations, framing, and load paths. We handle this in house so the design and engineering stay aligned.
• Permitting. We submit to the local jurisdiction, respond to plan-check comments, and carry the project through approval. ADU submittals have their own requirements, and we know what San Diego reviewers expect.
• Utilities and setbacks. We plan water, sewer, gas, and electrical connections, address whether a separate meter or panel upgrade is needed, and confirm the unit sits within required setbacks.
• Construction. Site prep and foundation, framing, rough mechanical, electrical, and plumbing, insulation and drywall, then finishes, cabinets, fixtures, and final trim.
• Final. We schedule inspections, complete the punch list, and hand you a finished, permitted, move-in-ready unit.

What an ADU Costs

ADUs are priced per square foot much like new construction, not by a single flat figure, because every site and design is different. As a general rule, a garage conversion costs the least, an attached unit lands in the middle, and a detached new-construction unit costs the most. The drivers that move your number are consistent:

• The size and type of the unit
• Site work, grading, and access to the build area
• Utility connections, including whether you need a separate meter, a panel upgrade, or a new sewer tie-in
• Finish level, from builder-standard to fully custom
• The condition of any existing structure being converted

Rather than guess at a number that may not fit your project, we will walk your property and follow up with a clear written estimate. Call (858) 267-4671 for a free in-home consultation and a real figure for your specific lot.

Why Use a Licensed General Contractor

An ADU touches design, structural engineering, permitting, utilities, and full construction. Trying to coordinate those pieces yourself usually means delays, finger-pointing, and surprises. As a full-service general contractor, we carry the entire project under one roof, which gives you a single point of accountability from the first walkthrough to the final inspection. We are a licensed, bonded, and insured California general contractor, license number 1004363, rated 4.7 stars across 45 Google reviews. If an ADU is on your radar, call (858) 267-4671 or request a free in-home consultation, and we will assess your lot, talk through the right unit type, and follow up with a written timeline and a fixed-price proposal.