Which Side of a Corner Lot Is the Front?

Before deciding whether an ADU fits on a corner lot, check which property line counts as the front. Two streets do not necessarily mean two identical front setbacks.

A recent customer question in Novato, California, illustrates the problem. The builder noticed that FutureLot was treating both street-facing boundaries as front lot lines. I reviewed the local code to determine which line was the front and which was the street side. That distinction mattered, but it was only half the answer. We also needed to check which ADU rules applied.

Start with the definition, not the front door

Novato’s zoning code states: “The front lot line on a corner lot is the line with the shortest frontage.” Where the street frontages are equal, the director determines which line is the front.

For the property we reviewed, that meant the shorter street frontage was the front lot line. The other street-facing boundary was the street-side lot line. The house’s entrance did not determine the answer under that definition.

This rule is specific to that jurisdiction, not a shortcut to apply everywhere. For each property, read the local definitions of lot lines and yards before assigning setback values. An unfamiliar lot configuration is a reason to check the code, not to assume the address tells you which edge is the front.

Then apply the rules for the proposed ADU

Correctly labeling the boundaries does not, by itself, tell you the required setbacks. You still need the rules for the proposed structure.

Novato’s published guidance lists a 4-foot street-side setback for a new detached ADU. For a larger detached ADU subject to the city’s Traditional Standards, the front setback generally comes from the underlying zoning district. In the R1-7.5 district involved in our review, the base front setback is 25 feet.

Those are two different requirements on the same lot. Applying the front setback to the street-side boundary could make a workable layout appear to have much less space. Applying the street-side setback to the actual front could make a layout appear to work when it does not.

The 800-square-foot distinction needs a closer look

Novato identifies a separate Limited Standards category tied to California Government Code Section 66323. For a qualifying new detached ADU of 800 square feet or less that meets the applicable height and other conditions, an additional local front zoning setback cannot be imposed.

California’s Department of Housing and Community Development distinguishes that category from ADUs reviewed under a local ordinance. For a locally regulated ADU, a city may apply a front setback, but it cannot use that requirement to prevent an otherwise qualifying 800-square-foot ADU from being built. If that unit fits elsewhere on the lot, the city may require the alternative location. A qualifying Section 66323 unit is not subject to that additional local front-setback requirement.

The practical point: do not treat “800 square feet” as a standalone permission to put any ADU anywhere. Identify the approval category and its conditions before drawing the setback lines. Building and fire requirements still need to be addressed.

Check the map before using it to test a layout

In FutureLot, review both the setback values and the Front, Side, and Rear labels on the map. Use View All Setback Scenarios and the source references to examine the conditions behind the displayed requirements.

If a lot-line label needs correction, open Edit > Edit Lot Borders. In the Novato case, I recommended changing the street-side boundary from Front to Side. That was a correction for this property and these ADU rules, not a recommendation to relabel every street-facing boundary as Side. Review the resulting setback values and lines before relying on the layout.

Changing a label in software does not change the zoning rule or establish a legal boundary. Where the boundary’s location is uncertain, use appropriate survey information rather than assuming a fence or curb marks it.

Before ruling out a corner lot, answer two questions: Which boundary does the code define as the front, and which setback applies to this particular ADU? The correct number on the wrong property line is still the wrong answer.