San Carlos Real Estate Guide
San Carlos’s ADU Boom: Real Local Costs and What They Can Earn
From garage conversion to full detached unit, real San Carlos numbers, not national averages
|
$120K to $500K+ Build Cost Range |
$2,000 to $4,000 Monthly Rental Income |
60 Days Typical Permit Processing |
20% to 30% Potential Property Value Boost |
San Carlos has genuinely leaned into ADUs as California’s housing laws have streamlined the process, and for homeowners weighing whether it’s worth it, the real local numbers tell a fairly compelling story.
Your Three Options in San Carlos
| ADU Type | Max Size | Typical Cost |
| Junior ADU | 500 sq ft, within existing home | Lowest cost, since it uses existing structure |
| Garage conversion | Up to 1,200 sq ft | Starting around $120,000 |
| Detached new-build ADU | Up to 1,200 sq ft | $150,000 to $500,000+ depending on size and finish |
Garage conversions remain the most cost-effective path, since the foundation, framing, and roofing already exist. Many of San Carlos’s ranch-style homes come with two-car garages that convert well into comfortable, code-compliant living space, and no replacement parking is required when converting a garage under current rules.
What an ADU Can Actually Earn Here
Real Numbers, Not Estimates
Data reported to the California Department of Housing and Community Development shows San Carlos ADUs generating roughly $2,000 to $4,000 a month in rental income. An 800 square foot unit renting at the higher end of that range can generate $36,000 to $48,000 a year, which over a decade adds up to $360,000 to $480,000, often exceeding the original construction cost by a wide margin.
Permitting Timeline
San Carlos has streamlined its ADU process in line with California state law, with most applications processed within 60 days and standard plan review taking roughly 4 to 6 weeks. Project complexity, site conditions, and how complete your initial application is can all affect the actual timeline.
Setback and Height Basics
| Minimum 4 foot side and rear setbacks for new detached ADUs |
| Height generally capped around 16 feet, with exceptions up to 25 feet for two-story ADUs in certain zones |
| Attached ADUs can be up to 50% of the primary dwelling’s size or 1,200 sq ft, whichever is smaller |
| No additional parking required in most cases, especially near transit |
Key Takeaway
With a streamlined 60-day permitting process and rental income routinely running $2,000 to $4,000 a month, an ADU in San Carlos can be one of the most financially productive projects a homeowner takes on, particularly starting from an existing garage.
Frequently Asked Questions
What’s the cheapest ADU option in San Carlos?
A garage conversion, starting around $120,000, since the existing structure eliminates foundation and framing costs.
How much rent can a San Carlos ADU realistically earn?
Roughly $2,000 to $4,000 a month, depending on size and finish quality.
How long does ADU permitting take in San Carlos?
Most applications process within 60 days, with 4 to 6 weeks typical for standard plan review.
Do I need extra parking for a new ADU?
Generally no, especially for properties near transit, and garage conversions specifically require no replacement parking.
| Related Reading | |
| ADUs on the Peninsula: Real Costs, Rental Income, and 2026 Rules | A wider regional look at ADU economics. |
| San Carlos Remodel and Addition Permits | General permitting rules that apply alongside ADU-specific ones. |
| The San Carlos Rental Market | See how ADU rents compare to the broader rental market. |
| What Upgrades Actually Increase Home Value in San Carlos, CA? | Compare an ADU against other value-adding projects. |
Considering an ADU for Your San Carlos Property?
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Holly Noto | Coldwell Banker Realty | DRE#01244498, DRE#01908304
580 El Camino Real, San Carlos, CA 94070
650.544.6185 | [email protected]
Cost and income figures reflect general San Carlos market reporting as of 2026 and vary by project, contractor, and location. This content is not construction, tax, or financial advice.
