ADU Resources Accessory Dwelling Units are additional structures located on a single-family lot. They can be attached or detached, and each city has specific regulations governing how they are built. Los Altos ADU Ordinance – October 2020Short Summary of the Los Altos ADU Ordinance General resources to get started: Casita CoalitionNapa Sonoma ADU – general content useful to allSymbium ADU Developers Click HERE to see a list of builders who completed an ADU and passed inspection in Los Altos as of September 2021. This list was pulled from city records. If you’d like to be added, please contact us.