About ADU Ledger

ADU Ledger is maintained by Ron Diver, a Seattle-area business owner and developer. It exists because Washington rewrote its ADU rules city by city through 2025–26, and the answers people actually find — search results and AI answers alike — lag the code by months or years.

Every fact on this site is cited to the municipal code section it comes from and verified against primary sources on a dated pass, with an independent adversarial fact-check before publication and a public changelog of every change and correction since. The methodology page describes the pipeline in full.

Most sites publishing ADU rules are anonymous. We think a named human who shows their work is the point.

Corrections

Spotted an error, a new ordinance, or a city we should cover? Email rondiver@gmail.com. Confirmed corrections are logged in the changelog with credit if you want it.