Garage Conversion ADU in San Diego: 2026 Cost Guide

By Cali Dream Construction | April 29, 2026 | CSLB #1054602

Converting your garage into an Accessory Dwelling Unit is one of the most cost-effective ways to add a livable unit to your San Diego property. Compared to building a new detached ADU from the ground up, a garage conversion uses an existing structure, which significantly reduces construction costs and timelines. Here is everything San Diego homeowners need to know about garage conversion ADU costs in 2026.

How Much Does a Garage Conversion ADU Cost in San Diego?

Garage conversion ADU costs in San Diego depend on the existing garage condition, the level of finish, and the scope of work required. Here are the ranges we see in our projects:

These costs include design, permits, construction, and standard finishes. They do not include furniture or landscaping.

What Is Included in a Garage Conversion?

Converting a garage into a livable ADU involves transforming a utilitarian space into a comfortable, code-compliant dwelling. The major work categories include:

Foundation and Floor

Most garage slabs are not insulated and may be lower than the main house floor level. The conversion typically requires raising the floor or adding insulation, a moisture barrier, and new flooring. If the existing slab has significant cracks or settlement, repairs are needed first. Floor work typically costs $3,000 to $8,000.

Walls and Insulation

Garage walls are usually uninsulated. California energy code requires proper insulation in habitable spaces. Framing out the walls with standard 2x4 framing, adding insulation, and finishing with drywall is a core part of the conversion. The garage door opening is framed in and filled with a standard wall, window, or entry door. Wall work runs $5,000 to $15,000.

Electrical

A garage typically has one or two circuits with minimal outlets and basic lighting. A livable ADU needs a full electrical system: dedicated circuits for the kitchen, bathroom, HVAC, and general use. Most conversions require a sub-panel or panel upgrade. Electrical work costs $5,000 to $12,000.

Plumbing

Adding a kitchen and bathroom where none existed requires running new water supply and drain lines. This is often the most complex part of a garage conversion because the garage slab needs to be cut and trenched for drain lines. Plumbing costs range from $8,000 to $20,000 depending on the distance to existing main lines and the number of fixtures.

HVAC

A mini-split heat pump system is the most common HVAC solution for garage conversion ADUs. They are efficient, do not require ductwork, and provide both heating and cooling. A single-zone mini-split system costs $3,500 to $6,000 installed.

Kitchen and Bathroom

The kitchen and bathroom are where much of the budget goes. A compact but functional kitchen with cabinets, countertops, sink, and appliances typically costs $8,000 to $20,000 for the fixtures and finishes alone. A bathroom with a shower, toilet, vanity, and tile work adds $6,000 to $15,000.

Garage Conversion ADU Permits in San Diego

Garage conversions require a building permit in San Diego. The good news is that California law has streamlined the permitting process for ADUs:

• No replacement parking is required when converting a garage to an ADU
• Impact fees for ADUs under 750 square feet are waived
• The city must approve or deny your application within 60 days of receiving a complete submittal
• Owner occupancy requirements have been relaxed under recent state legislation

Permit and plan check fees for a garage conversion ADU in San Diego typically total $3,000 to $6,000.

How Long Does a Garage Conversion Take?

• Design and engineering: 3 to 5 weeks
• Permitting: 4 to 8 weeks
• Construction: 8 to 14 weeks

Total timeline from consultation to move-in is typically 4 to 7 months. This is significantly faster than building a new detached ADU, which can take 8 to 14 months.

Rental Income Potential for a Garage Conversion ADU in San Diego

One of the primary motivations for building a garage conversion ADU is rental income. In San Diego County in 2026, a well-finished studio or one-bedroom ADU can command:

• Studio (400-500 sq ft): $1,500 to $2,200 per month
• One-bedroom (500-700 sq ft): $1,800 to $2,800 per month

At these rates, a $120,000 garage conversion can pay for itself in 4 to 6 years through rental income alone, before accounting for the increase in property value.

Common Challenges with Garage Conversions

• Ceiling height: Some older garages have ceilings below the 7-foot-6-inch minimum required for habitable space. Lowering the floor or raising the roof adds cost.
• Water heater relocation: If the main house water heater is in the garage, it must be relocated before conversion.
• Utility meters and panels: Electrical panels and gas meters in the garage need to remain accessible or be relocated.
• Drainage: Garage floors slope toward the door for drainage. This needs to be corrected for the new living space.

Cali Dream Construction specializes in garage conversion ADUs throughout San Diego County. We handle design, permitting, and construction from start to finish. Serving Carlsbad, Oceanside, Vista, San Marcos, Escondido, Encinitas, Poway, Rancho Bernardo, and all surrounding communities.