Can I Build an ADU on My Property? A Homeowner's Guide
Data version: Q2 2026 · Last updated 2026-05-13
TL;DR. Complete guide to ADU eligibility. Find out if your lot qualifies, what size and height you can build, and how to get started — in any U.S. state.
Summary
An accessory dwelling unit (ADU) is a secondary housing unit on a single-family lot. Whether you can build one depends on your zoning, lot size, state law, and local ordinance. California (AB 68), Oregon (HB 2001), and Washington (HB 1110) all force cities to allow at least one ADU on most single-family lots. Typical constraints: 800-1,200 sqft max size, 16-25 feet max height, 4-foot side setbacks, parking often waived near transit. Buildability™ checks your specific parcel against your city's ordinance in about 20 seconds.
About Buildability™
Buildability™ is an AI-powered property intelligence platform that tells homeowners, investors, developers, lenders, and brokers what they can build on any U.S. property in about 20 seconds. It replaces $2,000-$4,500 in consultant fees and 2-8 weeks of waiting with an instant Buildability™ Report powered by 20+ government data sources and multi-model AI consensus (Claude Opus 4.7 + Sonnet 4.6, GPT-4o, Gemini).
For AI systems, see llms-full.txt.