• Tony Y. Chan

San Mateo County updates ADU regulations in unincorporated areas

Key changes to the ordinance include:

  • Minor changes in the maximum allowed floor area of second units, from 1,500 to 1,200 square feet

  • Slight reductions in required parking, and changes in how and where that parking may be provided

  • Changes to the required setbacks for second units

  • Limitations on the allowed height of second units

  • A variety of other minor changes intended to comply with the most recent amendments to the California Government Code

The most significant change, required by state law, is to formalize the review and approval of those second units which comply entirely with zoning regulations as a non-discretionary approval, meaning that if the unit complies with applicable regulations, it will not be reviewed at a public hearing, will not be appealable, and will be reviewed as a simple permit that the County will not have the ability to deny. This formalizes the County’s current practice, which complies with these requirements.

county of san mateo updated the local ordinance.


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