Start here: researching your own Idaho ADU
This page is only useful if it's right. If you find a mistake, tell me and I'll fix it.
I'm building an ADU in Post Falls and publishing everything I learn along the way. This page puts that material in the order you'd want it if you're researching your own project.
1. Find out what's legal on your lot
Idaho's new ADU law, Senate Bill 1354, took effect July 1, 2026. It guarantees the right to build an ADU in cities over 10,000 people. It does not touch unincorporated county land, and covered cities have until February 1, 2027 to update their own codes, so right now a city's published rules can disagree with the state law. Where your lot sits decides everything. Start with my side-by-side read of the state law and the Post Falls code, then check your own city or county's code the same way.
2. See what you could build
If you're in Kootenai County, four free, pre-approved plan sets are published by a local housing coalition and reviewed by building departments across the county. Free plans that your building department has already seen are the fastest path I've found from idea to permit-ready drawings.
3. Price it before you commit
The money questions are the part nobody publishes. The Post Falls ADU tracker carries a running cost ledger for my own build: what I can price today and what I know is coming but can't price yet. Two answers from the City of Post Falls already changed my numbers. An ADU here shares the main house's water and sewer connection with no capitalization fee, and the city permits run $1,000 to $2,000 all in.
4. Know what to ask
Before you spend a dollar, read every question an Idaho ADU builder needs answered. It's the checklist I built for my own project, sorted into four buckets, and I add to it as readers send me the ones I missed.
5. Watch a real one happen
The build tracker shows where my project stands today: every question, every answer, every dollar, every step. The build log is the chronological record of how each answer got found.
What I can't help with yet
Financing, hiring a builder, and real start-to-finish timelines. Those are ahead of me too. When I learn them, they'll be published here.