Pierce County, WA Zoning Overlays & Bonuses: Density Bonus Law (2026)

Chapter 18A.65 PCC creates the county's affordable housing incentives program, adopted to meet the Growth Management Act's mandate that Pierce County provide for the housing needs of "all economic segments of the community." It applies to multi-family or single-family projects, including manufactured housing communities, in urban zones, but PCC 18A.65.020 expressly excludes the Residential Resource (RR) zone. Under PCC 18A.65.050.A, the density within all zones may exceed the maximum density set in Title 18A PCC for the entire site, including the portion not devoted to low-income housing.

Table 18A.65.050 A. sets the bonus math: 1.5 bonus market-rate units for every low-income rental unit and 1.0 bonus unit for every low-income owner-occupied unit, entire project area, capped by the density limitation table at 133% of maximum density in single-family residential zones and 120% of maximum density in multi-family or mixed-use zones that allow multi-family development. Accessory dwelling units are barred from developments that use this density bonus. To use the bonus, an applicant must sign an Affordable Housing Incentives Program Agreement with Pierce County Human Services and Planning and Public Works (PCC 18A.65.030.B) identifying every incentive claimed, the minimum number of affordable units required, and breach-of-contract terms; a breach lets the County place a lien against the project's properties.

Under PCC 18A.65.030.A, the affordability commitment runs with the land for 50 years (shorter durations are possible only if consistent with RCW 36.70A.540), secured by a recorded covenant and lien binding all successors. If a unit converts out of affordable use early, the owner must pay the impact fees in effect at conversion, and if only regulatory incentives (like the density bonus) were used, PCC 18A.65.030.G.1.b requires paying the County 20 percent of net sale proceeds. The Pierce County Human Services Department monitors continued affordability of both rental and owner-occupied units, and Planning and Public Works reports annually to the County Council on units built under the chapter.