By Alfred Twu
Also known as in-law units or granny flats, Accessory Dwelling Units (ADUs) are small homes added to lots that already have a house. They might be backyard cottages or basement or garage conversions. Compared to apartments, ADUs use fewer materials, and existing buildings are preserved. At $50,000-200,000 to build (roughly 1/3 the cost of a conventional apartment), ADUs add low-cost housing to existing neighborhoods, fighting sprawl, reducing commutes, and adding enough new residents to make transit and walkable businesses and amenities viable.
Berkeley and Oakland presently have ADU ordinances that allow ADUs of up to 750 square feet on lots that currently have a single house, with some restrictions on narrow streets. Additionally, State Bill 1069 took effect statewide on January 1st, making building ADUs easier by reducing utility fees, parking requirements, and streamlining approvals. To address traffic and parking concerns, some cities have policies where ADU residents are ineligible for residential parking permits.
Specifics on ADUs can be found at Berkeley Municipal Code section 23D.10 (search here), Oakland Municipal Code section 17.103.080 (search here), or California Government Code 65852.150 (search here). Your city's Planning Department can also provide you with information.
The large upfront cost, as well as requirements on owner occupancy of the main unit, setbacks, and door location, could challenge some homeowners. Financing programs similar to those used by rooftop solar could be offered by prefab and tiny house manufacturers to cover construction costs on installment plans. If subdivision and occupancy rules are relaxed, nonprofits and land trusts could also partner with homeowners to develop permanently affordable ADUs.
Image courtesy of Alfred Twu.