WHY BUILD AN ADU IN MARIN COUNTY?
Marin County homeowners are increasingly choosing to build ADUs as property values rise and rental demand grows. A well-built ADU in Mill Valley, Tiburon, or San Rafael can generate $2,500–$5,000/month in rental income while adding 15–25% to your property value. Under current California law (AB 2221 and SB 897), most single-family properties in Marin County can build one ADU and one Junior ADU by right — meaning the city cannot deny a compliant application. SolidBay specializes in navigating Marin County's local planning requirements, ensuring your ADU project gets approved and built efficiently.
Marin County ADU projects typically cost $180,000–$450,000 depending on type and finish level. Garage conversions are the most cost-effective option ($120,000–$220,000), while detached new-construction ADUs run $250,000–$450,000. Our in-house architects design your ADU to maximize livable space within your lot's constraints, and our permit expeditor handles all Marin County building department submissions. We serve Tiburon, Mill Valley, Sausalito, San Rafael, Corte Madera, Larkspur, Kentfield, Ross, Marin City, and Strawberry.