BuildabilityCan I Build an ADU? How to Check in Under 20 Seconds
The fastest way to find out if your property qualifies for an accessory dwelling unit — without calling the county.
Landon Reid Founder, Buildability™Updated 5 min read
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TL;DR: ADU eligibility depends on zoning, lot size, setbacks, and local rules. Buildability™ reads them where the city's code has been read (the Zoning Atlas lists which), and the free Score covers the hazards for any U.S. address — no signup required.
The ADU Question Everyone's Asking
Accessory dwelling units are the hottest trend in residential real estate. With new state laws in California, Oregon, Washington, and dozens of other states making ADUs easier to build, homeowners and investors are scrambling to find out: can I build one on my property?
The old way to answer that question involved calling your local planning department, waiting on hold, getting transferred, and — if you were lucky — getting a vague answer a few days later. If you wanted certainty, you'd hire a land use consultant and wait weeks.
What Determines ADU Eligibility?
ADU eligibility depends on a surprisingly complex set of factors:
Zoning Classification
Not all residential zones allow ADUs. Some require a conditional use permit. Others allow them by right under state preemption laws. This is the first thing to check — and the most common reason ADU plans fall apart.
Lot Size Minimums
Many jurisdictions require a minimum lot size (typically 4,000–6,000 sqft) before an ADU is permitted. Some states have overridden local minimums, but your city may still enforce them.
Setback Requirements
Your ADU needs to meet rear and side setback requirements, which vary by jurisdiction. Some states have reduced setbacks to as little as 4 feet under recent legislation — a game-changer for smaller lots.
Lot Coverage Limits
The total footprint of all structures on your lot (main house + ADU + garage) can't exceed the maximum lot coverage percentage. This is where many projects get stuck.
Owner-Occupancy Rules
Some cities still require the property owner to live on-site, though many states have eliminated this requirement. Check your local ordinance — this varies widely.
Utility Access
Your lot needs adequate sewer, water, and electrical capacity to support an additional unit. Connection fees are set by the water and sewer provider and can be a large line in an ADU budget, so ask for the provider's current schedule.
The 20-Second Alternative
What used to take weeks of calls and consultant time now takes 20 seconds. Buildability™'s ADU Buildability™ Report pulls from official government data sources to instantly determine:
- Whether your zoning district allows ADUs (by right or with permits)
- Your lot's setback requirements and remaining buildable area
- Maximum ADU size allowed under local and state regulations
- Estimated rental income potential based on local market data
- Environmental constraints (flood zones, fire hazard areas) that could affect construction
Instead of spending weeks on research, you get a comprehensive answer in 20 seconds.
What It Costs: Consultant vs. Buildability™
| Zoning Consultant | Buildability™ | |
|---|---|---|
| Cost | Quoted per engagement | Score free; Property Report $99 |
| Timeline | Weeks, by engagement | About 20 seconds |
| Data sources | Manual research | Live government APIs |
| Covers | Usually zoning only | Zoning + risk + environmental + market |
| Reusable | One property | Unlimited addresses |
A zoning consultant gathers this by hand over weeks. Buildability™ pulls the same data from live government APIs in 20 seconds. The Score is free; the Property Report is $99.
When to Start Your ADU Research
The best time to check ADU feasibility is before you need the answer:
- Before buying a property — Check ADU potential as part of your due diligence
- Before hiring an architect — Know your constraints before paying for plans
- Before talking to contractors — Have your zoning data ready to share
- Before refinancing — ADU potential can significantly impact property value
Check Your Property in 20 Seconds
Enter a U.S. address at buildability.us and get your Buildability Score™ instantly, with the ADU rules where the city's code has been read. The Score is free — no signup, no credit card.
The data a consultant gathers by hand is yours in 20 seconds, cited.