Los Altos has been working to adept ADU regulations to the local situation. The amendments to the city’s original ADU ordinance are needed to bring the code into compliance. The commission is scheduled to further discuss the potential changes at its May 7 meeting. The local newspaper has covered the news . In case you are wondering (like I was) what the daylight plane is: Daylight Planes are intended to provide for light and air, and to limit the impacts of bulk and mass on adjacent properties. “Daylight Plane” means a height limitation that, when combined with the maximum height limit, defines the building envelope within which all new structures or additions must be contained.
Palo Alto has a whole document (inspection checklist, no less) devoted to the topic.
To learn more on Los Altos specific ordinance please see the Los Altos website.
And there is more info on Los Altos and ADU, check out this event aptly called “The Nuts and Bolts of ADUs in Los Altos – It’s Easier in 2020″ organized by Los Altos Affordable Housing Alliance.