Accessory Dwelling Unit (ADU) Resource Center of San Mateo County

While this web page is oriented toward San Mateo County homeowners, many of the materials will be broadly useful to other parties and in other locations. It may also serve as a model for other cities and counties. 

This Guidebook was created as a resource to help homeowners build a second unit. It provides a detailed, step-by-step approach to the entire project — from getting started to becoming a landlord.

The workbook was designed to provide useful information and reduce the uncertainty in what can feel like a complicated process. Sections include:

• How to get started
• Designing your second unit
• Budgeting and finance
• Permitting and approvals
• Construction
• Move in (including resources on how to rent successfully) 

This calculator can help homeowners estimate the cost of converting part of their home into an ADU or constructing a rental unit.

These resources include pre-approved ADU plans, a guide to ADU finance, a guide to permitting and approvals, videos, slide decks and more.