Seattle, WA Zoning Overlays & Bonuses: Density Bonus Law (2026)
Key Facts
- Code
- SMC 23.58B-C
- On-site share
- 5-11%
- Fee range
- $7-$32/sq ft
- AMI cap
- 60% rent / 80% own
Summary
Seattle's Mandatory Housing Affordability program (SMC 23.58B-C) grants extra height and FAR in upzoned areas in exchange for on-site affordable units or in-lieu fees. MHA evolved from the 2015 HALA framework.
Mandatory Housing Affordability — Mandatory Housing Affordability (MHA) ensures that new commercial and multifamily residential development contributes to affordable housing. This is done by requiring new developments to include affordable housing (performance option) or contribute to the Seattle Office of Housing fund to support the development of affordable housing (payment option). MHA will provide rent-restricted, income-restricted homes for low-income people. This requirement is implemented by changing zoning to allow larger development and more housing. When developers and owners apply for new building permits, the Seattle Department of Construction and Inspection reviews each proposal to determine what MHA requirements the new development is subject to. Once these requirements are confirmed, the Office of Housing will review projects to coordinate with developers to comply with the MHA Program via the payment or performance option.
Full Breakdown
Adopted in 2019 after the Housing Affordability and Livability Agenda (HALA), MHA codified in SMC 23.58B and 23.58C requires developers in MHA-zoned areas to either build 5-11% affordable units on-site or pay an in-lieu fee ($7-$32 per sq ft, varying by zone and market area). The bonus permits an extra story, additional FAR, or relaxed yard standards. MHA applies to most multifamily and commercial projects of three or more units. Office of Housing administers fees and unit certification. Affordable units must serve households at 60% AMI for rentals or 80% AMI for ownership for at least 75 years. Map and fee tables are published online.
Violations & Fines
Failure to meet MHA affordability or pay fee: permit denial, stop-work, civil penalties up to $500 per day, and recovery of avoided contributions plus interest by Office of Housing.
Frequently Asked Questions
Does MHA apply to small additions?
Can I pay a fee instead of building affordable units?
Sources & Official References
- [1]MHA Program
- [2]SMC 23.58B
Other rules in Seattle
Compare Seattle to another location·View the Washington zoning overlays & bonuses overview
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Density Bonus Law in Nearby Cities
How other cities in King County handle density bonus law.