Permits in Sonoma County.

Well and septic permits come first

Permit Sonoma handles well and septic permits for the unincorporated county and for every city in it. For an ADU, the well and septic permits must be issued before the ADU building permit application.

On a well in a Class 3 or 4 groundwater availability area, an ADU needs a dry-weather well test, taken between July 15 and October 1. If the yield is not enough, or the net zero water requirement cannot be met, the county does not permit an ADU on the site. We check this before drawings start.

ADU Ready designs

Permit Sonoma's ADU Ready program lists pre-reviewed ADU designs, which shorten building review. A design must still be fitted to the site and submitted as a full building permit package. Parcels in the coastal zone need land use approval first.

Designs are valid only for the code cycle they were reviewed under. Permit Sonoma has noted that designs reviewed under the 2022 code are no longer valid. We confirm a design is current before building a package around it. See ADU permits.

Fire hazard zones

The state maps Fire Hazard Severity Zones. New buildings in a High or Very High zone may need to meet the wildfire construction standards in Chapter 7A of the California Building Code. That affects roofing, siding, vents, windows, and decks, so we check the zone before drawings start.

Fire rebuilds

We coordinate rebuilds after a fire, including a document set when drawings are required. Rebuild rules are set locally, so we confirm them with the reviewing agency at intake. See services.

Common questions

My property is in Santa Rosa. Who reviews the permit?

The City of Santa Rosa reviews the building permit. If the site has a well or septic system, Permit Sonoma still handles those permits, because its well and septic authority covers every city in the county.

Why do the well and septic permits have to come first?

For an ADU, Permit Sonoma requires them to be issued before the building permit application. Starting them early keeps the building permit from waiting.

Can I add an ADU on a property served by a well?

Often, yes. In a Class 3 or 4 groundwater area, the well must pass a dry-weather test and the project must meet the net zero water requirement. We check the groundwater class at intake.

Is an ADU Ready design approved for my lot?

Not on its own. The design is pre-reviewed, but it must be fitted to the site and reviewed as part of a full building permit package.