In Castro Valley, ADUs, also known as granny flats or in-law units, have become increasingly popular as a means to address housing shortages and provide additional living space on existing residential properties. These units typically include bathrooms to ensure they are self-contained and fully functional living spaces.

While governed by local building codes and regulations, requirements are subject to change, so it’s important to consult with the Alameda County Planning Department or a local building official to ensure compliance with the most current standards.  Here are some basic requirements:

  • Bathroom location and accessibility: ADU bathrooms must be located within the ADU structure and should be accessible without passing through any other dwelling unit. They should have a separate entrance for privacy.
  • Number of bathrooms: The number of bathrooms allowed in an ADU can vary depending on the specific zoning regulations and size of the property. In general, one bathroom is the minimum requirement for an ADU.
  • Minimum size and layout: ADU bathrooms must meet minimum size requirements for functionality and accessibility. These requirements can include minimum square footage, clear floor space for fixtures, and adequate ventilation.
  • Fixtures and amenities: A standard bathroom in an ADU typically includes a toilet, sink, and a shower or bathtub. The choice of fixtures may vary, but they should meet local plumbing codes and regulations. Keep in mind that it’s worth choosing highly accessible amenities, such as walk-in showers, if you plan on building your ADU for aging parents or other people with disabilities.
  • Plumbing and drainage: All plumbing and drainage systems in the ADU bathroom must be installed in compliance with local building codes. This includes proper wastewater disposal and connections to the main sewer or septic system.
  • Accessibility features: ADU bathrooms may need to be designed with accessibility features to accommodate individuals with disabilities. This can include wider doorways, grab bars, and accessible fixtures in accordance with the Americans with Disabilities Act (ADA).
  • Ventilation and lighting: Adequate ventilation and lighting are essential for ADU bathrooms. Typically, a bathroom should have a ventilation fan or a window that can be opened for air circulation. Adequate lighting is necessary for safety and functionality.
  • Permitting and inspection: Before constructing or remodeling an ADU bathroom in Castro Valley, it’s crucial to obtain the necessary permits from the local building department. Inspections will be required to ensure that the bathroom meets all relevant building codes.
  • Water efficiency: Castro Valley, like many California cities, places a strong emphasis on water conservation. Therefore, ADU bathrooms should include water-saving fixtures, such as low-flow toilets and faucets, to meet water efficiency standards.
  • Utility connections: The ADU bathroom must be properly connected to utility services, including water supply, electricity, and natural gas if applicable.

The bathroom requirements for ADUs in Castro Valley are subject to local building codes and regulations. These requirements may evolve over time, so it’s essential to consult with local authorities and professionals to ensure that your ADU’s bathroom complies with current standards. Additionally, keep in mind that the specific requirements can vary based on the property’s zoning, size, and other factors, so a tailored approach is often necessary to meet all relevant regulations.