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Top 10 Changes to the Building Codes you need to know

May 23, 2023

UPDATED MAY 23, 2023


While updates to Washington’s building codes have been delayed to late October, many of these significant changes may still impact your operations. Below is a list of the top 10 significant changes you need to be aware of.

1. WUI

The newly enforced Wildland Urban Interface (WUI) code applies a new set of standards to construction statewide to reduce property loss from wildfires. The Department of Natural Resources completed mapping of WUI zones for local jurisdictions to use for enforcement. Interestingly, the map doesn’t provide parcel-level detail

and provides the building official sole discretion over determinations of findings of fact. If you’re wondering what WUI covers, it’s everything from roofs, eaves, windows, doors, decking and much, much more.

2. Heat Pumps

In one of the most controversial decisions of the code cycle, the State Building Code Council (SBCC) adopted a mandate that all new housing units must be equipped with heat pumps for space and water heating—unless the new construction meets one of eight exceptions—think building sites with no access to electricity. While not a full ban on natural gas, this presents a very restricted opportunity under the code to use natural gas as a primary energy source for a home. You’ll see in the new R406 tables that project owners can still decide to use natural gas furnaces but it comes with a distinct disadvantage of -3.0 credits—forcing owners to gain credits in other (and more expensive) areas of the R406 table, regardless of whether or not they’re even able to connect to electricity.

3. Small Additions

Under the current code, additions less than or equal to 500 square feet had to meet 1.5 energy code credits for compliance with the code. Unsurprisingly, this created issues for homeowners seeking to add a walk-in closet or similar type of small addition. Under the newly adopted code, small additions 150 square feet and under will no longer have to adhere to energy code credit requirements.

4. Energy Code Credits

If there’s a silver lining in the heat pump mandate, it’s that it allowed the SBCC to adopt the less burdensome energy credit table. Small, medium and large dwelling units all saw reduction of at least a half credit.

Small (less than 1,500 sq. ft.) – 2.5 credits

Medium (1,500 sq. ft. to 4,999 sq. ft.) – 5 credits

Large (5,000+ sq. ft.) – 6 credits

Additions (150-500 sq. ft.) – 2 credits

Group R-2 – 4.5 credits

**Small additions (under 150 sq. ft.) are exempt from energy code requirements.

5. Air Leakage

In a win for the industry, Daimon Doyle, residential home builder representative on the SBCC, was able to negotiate an air leakage rate of 4 CFM instead of the proposed 3 ACH (the current rate is 5 CFM). During the November 4, 2022, code adoption meeting, Doyle stated, “there are so many factors that go into air sealing… builders need to be educated on how to get to 4 CFM. It’s a real struggle. There is no one-size-fits-all.”

6. EV Charging

Despite the International Code Council ruling that EV charging falls out of the scope of the International Residential Code, Washington has adopted this requirement in its version of the IRC. That means all new homes with attached private garages or attached private carports will have to pre-wire for EV charging. A minimum of one 40-amp dedicated 208/240-volt branch circuit must be installed in new electrical panels. The branch circuit should terminate at a junction box, receptacle outlet or EV charging equipment.

7. Lofts

The code is not silent on lofts anymore, as a code change submitted by the Washington Association of Building Officials has been adopted. Essentially, lofts are now treated as mezzanines in the code, as opposed to a habitable attic. These changes allow for a lower ceiling height, unrestricted use of space, and more.

8. Existing Buildings and Structures

Appendix J of the IRC has been moved (and restructured) to Chapter 45. There’s a whole host of changes to the code language that covers repairs, alterations, additions, and relocations that are worth checking out. A huge thank you to the City of Tacoma for submitting the adopted proposal that gives more flexibility for existing construction that should make it less expensive for existing homes to comply with the building codes.

9. Radon

If you build in a county that has to follow Appendix F because of high levels of radon, the new testing requirements may be a cause for concern. If your county requires radon reduction systems, you must achieve a test result at or below 4 pCi/L. If not achieved, further mitigation and re- testing must occur until 4 pCi/L or below is met. Proper planning for when to test for radon and mitigate is necessary to ensure this new requirement does not hinder closing status of homes in high- radon counties.

10. Kitchen Exhaust Rates

If you’re familiar with kitchen exhaust rates in the mechanical code, you’re probably aware that the current airflow rate is 100 CFM. With the new suite of code changes, this will change dramatically, depending on the type of range you’re installing in new homes. For example, a hood over electric range will now require at least 160 CFM, whereas a hood over combustion range will require a minimum of 250 CFM.

Enroll in BIAW’s series of codes classes statewide

BIAW has launched a series of codes classes statewide to help educate builders and remodelers on significant changes to the codes going into effect July 1, 2023. Taught by longtime codes experts, the courses will share the significant changes the State Building Code Council adopted and the new requirements the industry needs to meet to comply. Visit to learn more.


*This article was originally published in the May 2023 issue of Building Insight

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