Seattle, WA Building Safety: Anti-Mansionization (2026)
Floor-area-ratio (FAR) and bulk limits added to single-family zones to prevent oversized rebuilds, including LA's Baseline Mansionization Ordinance updates.
Research in progress
We are currently verifying Seattle's specific local ordinance for anti-mansionization. In the meantime,Washington state law generally applies, and below you'll find guidance for finding the official rules and links to related Seattle ordinances we've already verified.
Washington State Law Context
Washington state law provides the baseline framework for anti-mansionization across all municipalities in the state. Individual cities like Seattle may adopt additional local rules on top of state requirements, which is what makes checking your specific city ordinance important. For Seattle residents, the safest approach is to follow state law as a baseline and contact City Hall for any additional local requirements.
You can browse all Washington building safety to see how cities across the state regulate this topic.
How to find official Seattle Anti-Mansionization rules
- Search for "Seattle WA municipal code" to find your city's online code portal (Municode, eCode360, or American Legal Publishing are the most common).
- Look for chapters covering building safety, zoning, nuisance, or property maintenance — that's where most anti-mansionization rules live.
- Contact Seattle City Hall's code enforcement, planning, or community development department for clarification.
- Check with your HOA if applicable — many HOAs have stricter rules than the city itself.
Other building safety verified for Seattle
We've verified the following building safety for Seattle: