A local government may apply quantifiable, fixed and objective standards, such as height, setback,
and lot coverage requirements so the second-unit will be compatible with other structures in the
neighborhood. A local government may designate areas appropriate for second-units based on
criteria such as the adequacy of water and sewer services and the impact of second-units on traffic
flow. At the same time, a locality must adopt an ordinance with the intent of facilitating the
development of second-units in appropriate residential zones without arbitrary, excessive, or
burdensome provisions and requirements.
Under limited circumstances, a locality may prohibit the development of second-units in singlefamily
or multifamily zones (Government Code Section 65852.2(c)). This prohibition may only be
enacted if a locality adopts formal written findings based on substantial evidence identifying the
adverse impact of second-units on the public health, safety, and welfare and acknowledging such
action may limit housing opportunities in the region (Section 65852.2(c)). Prior to making
findings of specific adverse impact, the agency should explore feasible alternatives to mitigate and
avoid the impact. Written findings should also acknowledge efforts to adopt an ordinance
consistent with the intent of second-unit law.
A local government may also establish reasonable minimum and maximum unit size requirements
for both attached and detached second-units according to Government Code Section 65852.2(d).
Minimum and maximum unit sizes should be reasonable and should not arbitrarily and excessively
restrict the development of second-units. For example, a maximum unit size of 400 square feet
might be unduly restrictive on minimum lot sizes of 7,000 square feet, barring unusual
circumstances, and would restrict the development of second-units. Minimum unit sizes should
also uphold health and safety standards.