Author: Jackie Corley

Washington State is confronting a profound housing shortage that affects communities across all income levels. Statewide estimates indicate a deficit approaching one million housing units, a gap that has driven significant legislative, regulatory, and planning reforms. Within this environment, effective housing production depends on close coordination between public policy and design implementation, ensuring that legislative intent translates into buildable projects.

Legislative and Regulatory Drivers
Between 2022 and 2023, Washington State adopted multiple housing bills aimed at removing barriers to housing production. These reforms reflect an acknowledgment that local zoning and development standards may have unwittingly contributed to long-term underproduction. Key provisions of these statutes include requiring local communities to allow for two accessory dwelling units on many residential lots, authorizing missing middle housing types such as duplexes, triplexes, and courtyard apartments in formerly single-family zones, and enabling unit lot subdivisions that allow higher density and fee simple ownership without traditional large lot configurations. Collectively, these changes are intended to speed up housing delivery and expand choices across income levels.

From a civil engineering perspective, these policy shifts have direct implications for infrastructure. Additional Dwelling Units (ADUs) and increased density place new demands on water, sewer, stormwater, and fire flow systems. Designs should anticipate increased impervious area which equates to higher utility demand. The increased parking demand created by ADUs requires careful planning to meet parking requirements while maintaining adequate traffic flow for emergency vehicle access.

Comprehensive Plan Updates and Feasibility
Cities across Washington are updating their 20-year comprehensive plans as required by the Growth Management Act (GMA). Each jurisdiction is assigned housing targets based on different housing needs and income levels, and cities are now expected to show that their plans can realistically support that growth. Market-rate housing will not meet the affordability goals for residents earning less than 80 percent of the area median income , so public intervention may necessary in the form of working with housing authorities, nonprofits, and state funding programs for these projects to come to fruition.

AHBL recently assisted the comprehensive plan updates for communities including the City of DuPont, City of Edgewood, and City of Des Moines. A recurring challenge in these efforts is aligning infrastructure planning with allocated growth. Utility providers must plan for expanded capacity before new units generate revenue, creating cost and timing pressures. Civil engineering input is critical to assess capital facilities plans, identify realistic phasing strategies, and flag utility or roadway constraints that limit feasible density. In some communities, existing water or sewer systems were never designed for current density expectations.

Collaboration to Reduce Risk
Effective housing production depends on collaboration among developers, architects, surveyors, planners, and engineers. AHBL routinely supports developers delivering single family, missing middle, and multifamily housing through early-stage site feasibility reviews. Identifying offsite infrastructure requirements, access constraints, and stormwater challenges early allows clients to develop accurate budgets and confidence to proceed.

Strategies often help reduce entitlement risk, including alternative access layouts, shared utility approaches, and early coordination with local jurisdictions. Engaging wetland biologists, cultural resource specialists, and geotechnical teams early is especially important, as soil conditions and groundwater levels can significantly affect stormwater design, foundation systems, and project schedules.

Planning and Engineering for Specialized Housing
Housing production includes not only market rate and affordable units, but also age-restricted units including senior housing, retirement communities, and assisted living facilities. AHBL has worked on projects such as Wesley Homes and other senior housing initiatives, which bring unique civil engineering considerations. These projects often require careful grading to meet accessibility needs, well-connected pedestrian paths tied to transit, substantial parking for residents and staff, and robust emergency access and service areas. Stormwater and utilities must often be accommodated in dense urban sites, where vaults and compact systems are sometimes the only viable solution.

Energy Code and Site Coordination
Washington State’s new Energy Code requirements add a degree of complexity for projects aimed at providing affordable housing units. These standards influence building footprints, utility placement, and site layouts, including EV charging infrastructure and transformers. Our team is also experienced in planning all required “back-of-house” areas, including trash and recycling, generators, utility services, and other service related items. Close coordination among planners, architects, and civil engineers helps maintain site yield while meeting performance and accessibility standards.

Moving Housing Forward
State legislation, local code reform, and comprehensive planning in Washington are all aligned toward accelerating housing production. Projects that integrate land use planning and civil engineering early are best positioned to navigate rapidly evolving requirements and deliver housing at scale. With experience spanning planning, civil engineering, and institutional and affordable housing design, AHBL works alongside developers, housing authorities, and community partners to help address a key housing need across the state.

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