ADU Construction · Marin County
ADU Builder —
Marin County
Fully Permitted Accessory Dwelling Units Across Marin County
California's ADU laws have changed dramatically. Marin County homeowners can now build larger, more valuable accessory dwelling units than ever before. ConstruBay manages the entire process — design, permits, construction — delivering a fully permitted ADU on budget and on schedule.
Start Your ADU ProjectOptions
01
Detached ADU
A separate structure on your property. Maximum privacy and rental value. Up to 1,200 sqft in most Marin jurisdictions.
02
Attached ADU
An addition to your existing home. Cost-effective and ideal for multigenerational living.
03
Garage Conversion
Convert an existing garage into a fully permitted living space. Often the fastest permit path in Marin County.
04
Junior ADU
Up to 500 sqft within your existing home footprint. Minimal permit requirements under California law.
2026 Pricing
Marin County ADU Facts
California law now allows ADUs on most residential properties
Marin County permits ADUs up to 1,200 sqft detached
ADUs increase property value 15–20% on average
Rental income averages $3,000–$5,000/month in Marin County
Permit process averages 4–6 months in Mill Valley
FAQ
How much does an ADU cost in Marin County?
ADUs in Marin County range from $80,000 for a Junior ADU to $600,000+ for a large detached unit. All quotes include design, permits, construction and our 10-year warranty.
How long does ADU permitting take in Mill Valley?
ADU permits in Mill Valley average 4–6 months. We have established relationships with the Mill Valley building department that help expedite the process.
Can I rent out my ADU in Marin County?
Yes. Most Marin County jurisdictions allow ADU rentals. Average rental rates range from $3,000–$5,000 per month depending on size and location.
Start Your ADU Project
We assess your property's ADU potential and provide a complete fixed-price proposal within 5 business days.
Start Your ADU Project