As of April 2025, both Whatcom and Skagit Counties have adopted significant updates to their building codes, aligning with the latest state standards and introducing local amendments to address regional needs. Whether you’re planning a new construction project, a remodel, or an accessory dwelling unit (ADU), understanding these changes is crucial.
1. Onsite Sewage System (OSS) Regulations
In January 2024, the Washington State Board of Health adopted changes to Chapter 246-272A of the Washington Administrative Code (WAC), with most changes taking effect on April 1, 2025. Whatcom County has revised its local ordinance to align with these state updates. The revisions aim to clarify existing rules and address common issues, ensuring consistency with the new state regulations. The county has worked with local advisory groups to incorporate these changes, and the revised ordinance was adopted on March 11, 2025. Whatcom County
2. Accessory Dwelling Units (ADUs)
Starting July 1, 2025, House Bill 1337 prohibits cities from enforcing owner-occupancy requirements for ADUs statewide. This means that homeowners can rent out both the primary residence and the ADU independently, providing more flexibility and potential income opportunities. Additionally, the minimum size for ADUs has been standardized at 1,000 square feet, with local governments barred from imposing stricter limits. However, properties in the Lake Whatcom Watershed may retain restrictions to protect water quality. Bellingham ADU Builders+1A1DesignBuild+1
1. Adoption of 2021 International Codes
Skagit County has updated its building codes to reference the 2021 editions of the International Codes, replacing the 2018 editions. This update includes the International Residential Code, International Mechanical Code, Uniform Plumbing Code, International Fire Code, International Wildland-Urban Interface Code, International Energy Conservation Code, and the International Property Maintenance Code. The most significant changes are related to the Energy Code, reflecting advancements in energy efficiency standards. The Board of County Commissioners adopted these updated codes on August 24, 2021. City of Bellingham+2skagitcountywa.gov+2PublicInput+2PublicInput
2. Stormwater Management Regulations
In response to the National Pollution Discharge Elimination System (NPDES) Phase II Stormwater Permit for Western Washington, Skagit County has updated its stormwater regulations. These amendments aim to simplify stormwater construction regulations, incorporate low impact development (LID) practices, and maintain compliance with the permit. The updated regulations apply to development projects within the NPDES permit areas, which include Urban Growth Areas and certain flood hazard areas. skagitcountywa.gov
Stay Informed: Regularly check with your local planning and development departments for the latest code updates and interpretations.
Plan Ahead: Understanding code requirements early in the design process can help avoid delays and additional costs.
Consult Professionals: Work with architects, engineers, and contractors familiar with the latest codes to ensure compliance and quality construction.
Community Engagement: Participate in local workshops or public hearings to stay engaged with ongoing code updates and provide input on proposed changes.