Garage Conversion ADU in San Diego: Costs, Permits, and What to Know in 2026

By Fares Azani, Licensed General Contractor -- CSLB #1054602 | Published April 28, 2026

Converting a garage into an ADU is one of the most practical ways to add living space and rental income to a San Diego property. It is also one of the most misunderstood. Homeowners frequently underestimate the permit complexity and overestimate the simplicity of the build.

This guide covers what we have learned building garage conversion ADUs across San Diego County -- from Escondido to Coronado, from Poway to Chula Vista.

Why Garage Conversions Are So Popular in San Diego

Three reasons drive the demand:

1. California law (AB 68, SB 13, AB 881) makes it easier than ever. Cities cannot require replacement parking for garage conversions. Setback and lot coverage requirements have been relaxed. Most single-family lots in San Diego are eligible.
2. Existing structure reduces cost. You already have a foundation, walls, and a roof. Converting that shell into livable space costs significantly less than building a detached ADU from scratch.
3. San Diego rents justify the investment. A studio or one-bedroom ADU in most San Diego neighborhoods rents for $1,500-$2,500 per month. At conversion costs of $80,000-$150,000, the payback period is typically 4-7 years.

What Does a Garage Conversion ADU Actually Cost in San Diego?

The Permit Process for a Garage Conversion ADU

Despite California's ADU-friendly laws, you still need a full building permit. Here is the process in San Diego:

1. Site assessment. Measure the garage, confirm lot zoning, check setbacks, verify sewer and utility access.
2. Architectural plans. Floor plan, elevations, electrical plan, plumbing plan. Title 24 energy calculations are mandatory.
3. Structural engineering. If modifying the garage door opening (which you will), a structural engineer sizes the new header and any required framing modifications.
4. Submit to City of San Diego (OpenDSD) or County. The city has a streamlined ADU review track. Plan check currently takes 3-6 weeks for ADUs.
5. Address plan check corrections. First-pass approval is possible but not guaranteed. Budget 1-2 correction cycles.
6. Permit issuance. Pay fees, receive approved plans. Construction can begin.
7. Inspections. Foundation, framing, rough MEP, insulation, drywall, final.
8. Certificate of occupancy. After final inspection, the ADU is legally habitable.

Common Permit Pitfalls

• Parking is NOT required. Under state law, the city cannot require you to replace the parking spaces lost by converting the garage. Some homeowners do not know this and get scared off by outdated advice.
• Setback relief. Existing garages that are within 4 feet of the property line can typically remain in their current footprint for the conversion. You do not need to demolish and rebuild further back.
• Impact fees waived. Units under 750 sq ft are exempt from impact fees in most San Diego jurisdictions.

What Does the Construction Actually Look Like?

A typical garage conversion takes 3-5 months from permit approval to move-in. Here is the general sequence:

1. Remove garage door, frame in the new wall with windows and entry door
2. Pour new concrete or raise the existing slab (garage slabs are usually lower than the house floor level)
3. Frame interior walls for bathroom, closet, and kitchen layout
4. Rough in plumbing, electrical, and HVAC
5. Insulate walls and ceiling per Title 24
6. Hang drywall, tape, and texture
7. Install flooring, cabinets, countertops, fixtures
8. Paint, trim, hardware
9. Final inspections and certificate of occupancy

Is the ROI Worth It?

Beyond the numbers, a garage conversion ADU also provides flexibility: housing for aging parents, a home office that is truly separate from the house, or a guest suite that can shift to rental when needed.

5 Things Most Contractors Will Not Tell You

1. Not every garage is a good candidate. Some garages have slab issues, poor drainage, or structural problems that make conversion more expensive than a ground-up build. We assess this honestly during the initial site visit.
2. The garage door opening is structural. Framing it in properly requires engineering. A cheap framing job here creates problems later.
3. You need a separate address and utility meter. The ADU needs its own address for legal rental. Some jurisdictions require a separate electrical meter.
4. Ceiling height matters. Habitable rooms need at least 7'-6" clear ceiling height. Some garages barely meet this, especially after raising the floor and insulating the ceiling.
5. Sewer scope before you start. We always recommend a sewer camera inspection before construction. If the existing sewer line is damaged or undersized, you need to know before committing.

Bottom Line

A garage conversion ADU is one of the highest-ROI construction projects available to San Diego homeowners right now. California law supports it, San Diego rents justify it, and the conversion cost is substantially less than new construction.

But the quality of the build matters enormously. A well-built ADU with proper permits, insulation, and finishes will command top rent and add real value to your property. A poorly done conversion with code issues will be a headache for years.

If you are considering a garage conversion, start with a site visit from a licensed contractor who can give you honest numbers. Call us at (858) 434-7166 or request a free estimate online.

Cali Dream Construction -- Licensed General Contractor, CSLB #1054602. Serving all of San Diego County.