Building an accessory dwelling unit in Marin requires spending a lot of money and navigating a thicket of rules, regulations and fees. To meet ambitious state-mandated housing targets, the Marin County Civil Grand Jury is urging the county to streamline the process and make it more affordable.

ADUs—also known as in-law apartments or granny units—are a significant component of Marin’s strategy for increasing housing stock. The county has already implemented some programs aimed at getting…