Our Data Collection Process
Every data point on ADU Zoning Hub is sourced from official government records and verified market data. We don't rely on secondary sources or AI-generated content for regulatory information. Here's exactly how we collect and verify each type of data:
Zoning & Setback Data
Primary Sources: Municipal codes, city zoning ordinances, and official planning department publications.
For each city, we locate the specific municipal code section governing Accessory Dwelling Units (often found under residential zoning chapters). We cross-reference this with the city's planning department website, which typically publishes ADU-specific information sheets, handouts, or web pages summarizing the rules.
What we verify: Allowed zones, maximum unit sizes, height limits, setback requirements, parking rules, owner-occupancy requirements, and lot size minimums.
Permit Process & Fee Data
Primary Sources: City planning department permit pages, published fee schedules, and ADU-specific application guides.
Permit fees and timelines come from official city fee schedules (which most cities publish as PDFs or web pages). Processing timelines reflect state-mandated minimums (e.g., California's 60-day ministerial review) combined with city-reported averages.
What we verify: Approval process type (by-right vs. conditional use), review timeline, permit fees, impact fees, plan check requirements, and pre-approved plan availability.
Construction Cost Data
Primary Sources: HomeAdvisor/Angi contractor cost databases, city-published fee schedules, and regional construction cost indices.
Construction costs are estimates based on regional averages from contractor marketplaces and adjusted for local labor and material costs. We present ranges rather than exact figures because actual costs vary significantly based on ADU type, size, finishes, and site conditions.
Important note: Cost estimates are for general guidance only. Always get multiple contractor quotes for your specific project.
Rental Income Data
Primary Sources: Zillow Rental Manager market data, HUD Fair Market Rents (FMR), and local rental market surveys.
Rental income estimates represent typical market rents for studio/1BR and 2BR units in each city's metro area. These figures are updated to reflect current market conditions using publicly available rental indices.
Important note: Actual rental income depends on location within the city, unit quality, amenities, and market conditions at the time of listing.
Source Types
| Municipal Code | Official city ordinances and zoning code sections — the legal text governing ADU regulations |
| Planning Department | City planning/building department websites, information sheets, and published guides |
| Government Data | State-level legislation, HUD data, and other official government publications |
| Market Data | Construction cost databases (HomeAdvisor, Angi) and rental market data (Zillow, HUD FMR) |
| News Source | Verified news reporting on legislative changes, used to supplement official sources |
Verification & Update Schedule
We aim to verify data for each city on a quarterly basis, with priority updates triggered by:
- New legislation: When a state or city passes new ADU laws (e.g., California's annual ADU bills, Massachusetts' Affordable Homes Act)
- Ordinance changes: When a city amends its zoning code affecting ADU regulations
- User reports: When site visitors flag potential inaccuracies (report via our contact page)
- Scheduled review: Full data audit at least once per quarter for high-traffic cities
Each city page shows a "Verified" date indicating when we last confirmed the data against official sources. The specific source URLs are listed at the bottom of each city page under "Sources & References."
Data Accuracy Disclaimer
ADU Zoning Hub provides information for general guidance only. While we make every effort to keep our data accurate and up-to-date, ADU regulations change frequently and may vary based on specific property characteristics.
Before making any decisions about building an ADU, we strongly recommend:
- Confirming current rules with your local planning department
- Consulting with a licensed architect or contractor familiar with local ADU regulations
- Checking for any overlay zones or specific conditions that may apply to your property
If you notice any inaccuracies in our data, please contact us so we can investigate and correct the information promptly.
City Source Coverage
Below is our current source coverage by city. Cities marked with government sources have direct links to official municipal codes or planning department pages.
| City | Government Sources | Market Data Sources |
| Los Angeles, CA | 6 sources | 4 sources |
| San Francisco, CA | 5 sources | 4 sources |
| San Diego, CA | 4 sources | 4 sources |
| San Jose, CA | 4 sources | 4 sources |
| Sacramento, CA | 4 sources | 4 sources |
| Oakland, CA | 2 sources | 4 sources |
| Long Beach, CA | 3 sources | 4 sources |
| Fresno, CA | 2 sources | 4 sources |
| Santa Ana, CA | 3 sources | 4 sources |
| Anaheim, CA | 2 sources | 4 sources |
| Austin, TX | 4 sources | 4 sources |
| Houston, TX | 2 sources | 4 sources |
| Dallas, TX | 3 sources | 4 sources |
| San Antonio, TX | 3 sources | 4 sources |
| Fort Worth, TX | 2 sources | 4 sources |
| Miami, FL | 5 sources | 4 sources |
| Tampa, FL | 3 sources | 4 sources |
| Orlando, FL | 3 sources | 4 sources |
| Jacksonville, FL | 2 sources | 4 sources |
| Portland, OR | 5 sources | 4 sources |
| Eugene, OR | 2 sources | 4 sources |
| Salem, OR | 2 sources | 4 sources |
| Bend, OR | 3 sources | 4 sources |
| Seattle, WA | 5 sources | 4 sources |
| Tacoma, WA | 3 sources | 4 sources |
| Spokane, WA | 2 sources | 4 sources |
| Vancouver, WA | 3 sources | 4 sources |
| Denver, CO | 5 sources | 4 sources |
| Colorado Springs, CO | 3 sources | 4 sources |
| Boulder, CO | 4 sources | 4 sources |
| Boston, MA | 6 sources | 4 sources |
| Cambridge, MA | 2 sources | 4 sources |
| Worcester, MA | 2 sources | 4 sources |
| New York City, NY | 6 sources | 4 sources |
| Buffalo, NY | 3 sources | 4 sources |
| Rochester, NY | 2 sources | 4 sources |
| Phoenix, AZ | 5 sources | 4 sources |
| Tucson, AZ | 2 sources | 4 sources |
| Scottsdale, AZ | 2 sources | 4 sources |
| Charlotte, NC | 1 sources | 4 sources |
| Raleigh, NC | 2 sources | 4 sources |
| Durham, NC | 2 sources | 4 sources |
| Atlanta, GA | 1 sources | 4 sources |
| Savannah, GA | 1 sources | 4 sources |
| Minneapolis, MN | 6 sources | 4 sources |
| Saint Paul, MN | 4 sources | 4 sources |
| Chicago, IL | 3 sources | 4 sources |
| Evanston, IL | 1 sources | 4 sources |
| Arlington, VA | 1 sources | 4 sources |
| Alexandria, VA | 1 sources | 4 sources |
| Ontario, CA | 2 sources | 0 sources |
| Riverside, CA | 2 sources | 0 sources |
| San Bernardino, CA | 2 sources | 0 sources |
| Rancho Cucamonga, CA | 2 sources | 0 sources |
| Fontana, CA | 2 sources | 0 sources |
| Nashville, TN | 2 sources | 0 sources |
| Salt Lake City, UT | 2 sources | 0 sources |
| Honolulu, HI | 2 sources | 0 sources |
| Washington, DI | 2 sources | 0 sources |
| Pittsburgh, PA | 2 sources | 0 sources |