Every California county, including Marin, is under the state Legislature’s gun to build thousands of new units of housing. The Regional Housing Needs Allocation numbers imposed on each county and municipality must be satisfied or draconian penalties will be imposed.

The state’s mandates include requirements for market-rate million-dollar homes as well as workforce housing. The latter is the category that California truly needs to create economically diverse communities.

Marin County’s Civil Grand Jury just issued a first-class report entitled, “Build More ADUs — An Rx to Increase Marin’s Housing Supply.” Accessory dwelling units can either be detached from the main home or be “junior ADUs,” which are built within the walls of an existing detached structure. They form the most economically productive and least intrusive way to construct affordable homes.

The report is an analysis of ADUs and positive steps that the state has taken to encourage their construction. It also included a list of bureaucratic inhibitors that Marin communities have — usually due to a “we’ve always done it this way” process.

Some assert that any new housing including ADUs adds to traffic congestion and will burden overextended schools, police and fire services. While likely true, it’s irrelevant since the state will compel localities to build more housing. It’s better to encourage affordable housing with the “gentle density” approach of ADUs than going with high-density multi-unit structures. Unless they are exceptionally well designed, those buildings can obliterate any neighborhood’s character.

According to a Association of Bay Area Government survey, “When accounting for ADUs rented at market rates, and ADUs rented at discounted rates to families and friends, 29 percent are affordable to very low income households, 44 percent to low income households, 26 percent to moderate income households, and 7 percent to above moderate income households.”

Adding an ADU to a Marin home should be much easier. Despite the state’s intentions, gaining approval for an ADU is a cumbersome procedure. Despite state law, it’s a needlessly cumbersome procedure in Marin.

Almost all governmental entities levy mitigation and impact fees on construction of ADUs. The grand jury uses Novato as an example. There, fees charged on a new ADU total $18,446 when the unit is 700 square feet and jumps to $34,307 when it’s 800 square feet. In addition to those charged by the city, additional fees include Novato Sanitary District ($12,000 per dwelling unit), North Marin Water ($8,675), Novato Unified School District (a 700-square-foot unit is exempt, but an 800-square-foot ADU costs $3,264). Novato’s fire district admirably exempts ADUs. In central and southern Marin, Marin Municipal Water District charges no ADU impact fee.

At least Novato residents know what it costs. I went to Corte Madera’s Building Department and inquired about costs if I added an ADU to a single-family home. The reply was “we can’t tell you until you bring in plans.” That’s because the town’s charges are based on how much time it takes to analyze the plan. Without details they can’t compute the fees. Few homeowners will retain an architect without knowing the basic question of what fees they’ll pay.

As the report explains, local governments and school districts have “turned to development fees … to generate revenue. Given that California (governments) have tightly restricted funding sources, fees are one of the few ways cities can pay for the indirect costs of growth. If adding low impact affordable housing is the goal, then the model should be the Novato Fire District’s feeless process.

Currently, all 11 Marin municipalities and our county government set different guidelines for allowing ADUs. A better approach is for them to expand their ADU coordination efforts by creating uniform practices and standards applicable throughout Marin.

Columnist Dick Spotswood of Mill Valley writes on local issues Sundays and Wednesdays. Email him at spotswood@comcast.net.