The State of California has Public Resource Codes (PRC) 4290 and 4291. PRC-4291 prescribes the requirement for 100' defensible space around an improved building found in the state responsibility area (SRA). This is the statewide standard and what defensible space inspection (DSI) programs utilize. This code is applicable to all businesses and residences (improved parcels) that are not in an incorporated city or town, thus they are in the SRA. The City of Grass Valley, Nevada City, and the Truckee Fire Protection District each have their own vegetation ordnance, so you should look to the specific agency in which your home resides in for details. Nevada County Consolidated Fire District has Fuel Modification Standards that apply to vacant parcels if they reside in their fire district boundary.
PRC-4291 is applied to a single property at a time in the SRA. The SRA is fundamentally the unincorporated county area. As such, Nevada County has a vegetation ordinance that builds on this code. First, if a home cannot achieve their needed 100' of defensible space due to their property line being less than 100' from their home, it requires the adjacent property owner to accommodate the additional space needed to obtain the full 100'. Second, it adds the requirement for property owners that are along a private road that is a critical egress route to mitigate the vegetation 10' back from the roadside edge and trimmed up 15" high. The County ordinance only applies in the unincorporated county area and includes a fee structure and abatement program.
You can find all the ordinances mentioned here online with at each agencies' public website. Learn more about preparing your property and specific laws and ordinances in our Ready section. https://www.mynevadacounty.com/2710/Ready