Building Codes

Every three years, new model construction codes are published through the International Code Council (ICC). The State Building Code Council (SBCC), with the assistance of their Technical Advisory Groups (TAGs), adopts the amendments.

*** The SBCC has delayed implementation of the 2021 Residential Code, Energy Code and WUI Code until Oct. 29, 2023 **

2018 Residential Construction Code in Effect February 1, 2021

The SBCC has adopted the 2018 editions of the International Building Code (IBC), International Residential Code (IRC), International Fire Code (IFC), International Mechanical Code (IMC) and Uniform Plumbing Code (UPC) with state amendments; and the 2018 Washington State Energy Code (WSEC). The 2018 code becomes effective February 1, 2021.

Washington State Energy Code Updates

The 2018 Washington State Energy Code, which is actually a combination of the 2018 International Energy Conservation Code (IECC) and the 2015 Washington State Energy Code (WSEC), has now been divided into commercial and residential provisions – both are available to download below:

Based on the 2018 IECC, “Residential” includes one- and two-family dwellings, townhouses and group R-2 and R-3 buildings three stories or less. “Commercial” includes all buildings not covered under “residential.”

Below are highlights of the revisions of the significant changes to the WSEC:

Energy Code Changes

Per RCW 19.27, permitted construction must achieve 70% reduction in annual net energy consumption by 2031 using 2006 Wa. State Energy Code as the base level.  Continued incremental changes have been made this code cycle for fuel source selection, envelope air leakage control, ventilation system effectiveness, HVAC efficiencies, hot water generation equipment, renewable electric energy and lighting equipment.

Changes to Energy Code Credits

A dynamic shift takes place in the 2018 WSEC. “Carbon emissions equalization” between heating source fuels incentivizes high-efficiency heat pump HVAC equipment and renewable energy generation (wind/solar). Penalties are incorporated for combustion-fuel and electric-resistance equipment.

Required additional “credits” now includes R-2 occupancies. Dwellings:

    • Less than 1,500 sq. ft. require 3 credits (previously 1.5);
    • 1,501-4,999 sq. ft. require 6 credits (previously 3.5); and
    • 5,000+ sq. ft. require 7 credits (previously 4.50).

R-2 dwellings require 4.5 credits (previously 2.5) and residential additions less than 500 sq. ft. require 1.5 credits (previously 0.5).

2018 WSEC introduces a new appliance package credit option. Installed appliances must be Energy Star rated and include a ductless clothes dryer without vent ducting or exterior vent caps installed in the building.

New Simulated Performance Metrics

Building designs using the Simulated Performance Alternative method (comparing a standard reference design to a proposed design) now must show reduced annual energy consumption based on “carbon emissions” of the fuels and energy use in the proposed building design.

Building Code Planning Changes

The 2018 IRC includes updates to climate, geographic and seismic design criteria. Building departments must now provide “Manual-J” local design criteria for heating/cooling calculations.

Two-Family Dwelling Separation

2018 IRC references the 2018 IBC (non-residential construction), incorporating tried & true methods for constructing fire-resistance wall assemblies used in commercial construction.

The code permits a half-hour fire-resistance wall rating in buildings equipped with an automatic fire sprinkler system.

Updated Safety Glazing and Stairs

The code modifies requirements for safety glazing adjacent to doors as well as emergency escape and rescue openings. It also clarifies handrail projections on stairs and increases new standards for max stair rise between landings, recognizing use of taller engineered floor joists for longer open spans and space for HVAC ducting.

Heat, Smoke & CO Sensors

The codes now requires “heat-detection” devices in garages and updates placement locations for smoke detectors near bathrooms. Updated carbon monoxide alarm standards allow builders to utilize new wireless sensor technology in their projects.

Photovoltaic/Solar Energy Systems

Newly defined pathway clearances around PV roof panel placements provide firefighter access and clearance for emergency escape/rescue openings.

Mezzanine Areas, Habitable Attics and Sleeping Lofts

Mezzanines can now be increased to half the area of the room containing the mezzanine if a sprinkler system is added. Definition of “habitable attic” has been changed to “a finished or unfinished habitable space within an attic.” The Washington state amendment added this space (with exceptions) to be considered a “story above grade plane.” Amendments address new standards for sleeping lofts in “condensed dwelling units” to include limits for floor area, access/egress requirements, headroom, tread/riser sizing, handrails and landing dimensions.

Family Homes and Radon Protection

The SBCC added a section for Adult Family Homes specifying grab bar placement, handrail/riser dimensions and door lock installation regulations. An SBCC amendment requires radon control provisions (Appendix F) applicable to buildings constructed in high radon potential counties (Clark, Ferry, Okanogan, Pend Oreille, Skamania, Spokane and Stevens). Per the amendment, unvented crawl spaces will not be allowed for these counties.

Footing Sizes and Deck Framing

A state amendment provides alternative footing size graphs for light-frame construction (per snow load). The state amendment provides new design tables for a required increase to 2018 IRC live loads, materials, posts, joists and lateral support for decks.

Stud Height, Lateral Support for Headers and Water-Resistive Barriers

The 2018 IRC provides updated design tables for taller stud height, lateral support for headers, water resistive barrier installation criteria, roof framing and chimney insulation barriers.

Mechanical and Gas Code Changes

Clearance requirements around furnaces are now deferring to manufacturers’ specifications. Makeup air for high-volume kitchen exhaust systems is clarified. PEX tubing support placement recognizes larger diameter supply piping. Gas-fired clothes-dryers may now be installed in bathrooms where permanent openings communicate with other permitted spaces. The 2018 IRC appendices include updates for tiny houses, straw-clay construction, straw-bale construction, solar-ready zones and fire sprinklers.

BIAW’s 2018 Code Changes

If you missed the chance to attend BIAW’s 2018 Codes class, you can download and view the 2018 Significant Code Changes PowerPoint presentation.

Sign Up for BIAW Codes Classes

The Building Industry Association of Washington is providing a more in-depth discussion of these updates in (on-line) codes training classes. The BIAW instructors for the “2018 Significant Code Changes” classes are industry professionals, providing insight and examples of how builders can implement these code changes in their projects.

Additional Resources for Building Codes

International Code Council

You can purchase I-Codes books from the International Code Council. If you are an ICC member, contact Andrea Smith to receive the member discount.

WABO Bookstore

Code books can also be purchased from:

WSU Energy Program

The WSU Energy Program also provides a variety of resources to assist you in complying with new energy code.

BetterBuilt NW

BetterBuilt Northwest is a resource center designed to support and promote energy-efficient home building in the region.


If you have any questions regarding residential building codes and regulations, please contact Government Affairs Assistant Director Josie Cummings at (360) 352-7800 ext. 163.