The Design Brief | Volume I | What’s New In Residential Building Codes For Single-Family Homes in 2024
Residential building codes can be a daunting topic for interior designers. They are complex, lengthy, and written in legalese. But interior designers shouldn’t feel apprehensive about having a thorough understanding of the codes pertaining to single-family residences.
Our first Design Brief will cover basic information about code formatting and application, as well as share the most significant changes that have been made in the last several years.
For a thorough documentation of residential code requirements for specific building features (stairways, fireplaces, electrical outlets, lighting), be sure to check out our Residential Building Codes Handbook.
Building codes are intended to ensure greater safety within the built environment, not to add needless requirements or costs to building construction. In the United States, single-family homes and duplexes are mostly regulated by the International Residential Code(IRC), which is free to access online here. The IRC is in use or adopted in 49 of the 50 states, plus Washington DC, Puerto Rico, and the US Virgin Islands. Wisconsin uses their own hybrid Residential Code, but it is closely based on the IRC. In Canada, codes for housing are covered in Part 9 of the National Building Code of Canada.
Any building larger than a single-family or duplex residence is regulated by the more expansive International Building Code and other code publications that regulate mechanical, plumbing, and electrical applications. The IRC is largely comprehensive in that it includes mechanical, electrical, and other considerations for single-family homes and duplexes. However, other code documents and standards are referenced within the text.
Most building codes—including the IRC—are updated every three years to encompass emerging building construction strategies. The current version of the IRC was published in the Spring of 2024, with upcoming versions scheduled for 2027, 2030, 2033, and so on. However, each individual municipality (city or township) can choose which version they adopt and when, provided they are utilizing codes published within the previous ten years. Check with the municipality’s building department website (where the project home is located) to verify which version is being enforced.
Several notable changes have been made to the IRC in the last few years, which are summarized below.
ACCESSORY DWELLING UNITS (ADUs)
The most recent (2024 version) IRC added an appendix (Appendix BC) to address the issue of Accessory Dwelling Units (ADUs).
An ADU is a second dwelling on a property to allow an additional individual or family unit to reside on the same building lot as a larger single-family home. An ADU may be attached or detached from the primary home building. This provides consideration of the aging of the population in the United States, where now 1 in 6 people is over the age of 65.
An ADU may be the most affordable and practical way to house an older family member, as compared with other senior housing options. The potential for an ADU on a residential property also responds to low-income housing shortages. And an ADU can provide a means for supplemental income (renting to tenants) for homeowners, as well as a way of increasing property values.
Zoning regulations related to ADUs vary widely across the country, but California, Oregon, Washington, and Colorado have led the way in allowing—and even promoting and simplifying—ADU permitting and construction.
What the 2024 IRC accomplished was to provide specific limitations for ADUs to distinguish them legally from a second dwelling or duplex.
Under these guidelines, an ADU:
Can be within, adjacent to, or detached from the primary residential building, but cannot be less than 190 square feet or more than 1,200 square feet in size.
Must be less than half the size in square feet as the primary residence.
Must have its own entrance door (means of egress).
Cannot have more than two bedrooms.
Local ordinances within individual municipalities will also have requirements or stipulations on ADUs.
OUTLETS ON A KITCHEN ISLAND OR PENINSULA
The other most notable change to the IRC 2024 (as well as the 2023 National Electrical Code) was a change to the requirement for outlets (called receptacles or receptacle outlets in the code) on a kitchen island or peninsula.
In previous code versions, an outlet was required to be installed at the end of an island or peninsula of any size, no lower than 1’ below the countertop surface. Where the island’s counter size was greater than 9 square feet, an additional outlet(s) would be required.
This proved to be a risky solution to providing power at kitchen islands and peninsulas, as children, pets, or passing objects could catch a dangling cord and pull down a heavy appliance or device from the countertop, or the hot contents of a countertop cooking appliance.
So with the 2023 National Electrical Code, as well as the 2024 IRC, a receptacle outlet can no longer be installed on the cabinet ends of an island or peninsula.
One of three alternate options is allowed:
An outlet can be installed above the countertop surface, but no higher than 20” above the countertop. This outlet could be on a wall or step up to an adjacent bar-height counter.
An outlet can be installed directly in the countertop. This could be a pop-up or flush assembly designed specifically for countertop applications.
Installing no outlet in the countertop is allowed, providing electrical wiring is brought to the island or peninsula so that an outlet could be added at a later date.
Remain aware that—if the 2024 IRC has not yet been adopted by the municipality where a residential project is located—this code change may not apply, and the previous requirement for an outlet at the end of an island or peninsula would still be applicable.
It is always advisable to check with the local building department for answers to any questions about enforced codes. To do that,simply call the building department in the municipality (city or township) where the home is located and inquire.
If this content was informative, and you want to be notified of any future building code changes that might affect your residential design work, be sure to check out our Residential Building Codes Handbook. Once you purchase, you’ll be added to the update list for all codes related changes.
SOURCES: Caplan, Z. (2023, May 23). U.S. Older Population Grew From 2010 to 2020 at Fastest Rate Since 1880 to 1890. United States Census Bureau. https://www.census.gov/library/stories/2023/05/2020-census-united-states-older-population-grew.html
International Code Council. (2024). 2024 International Residential Code. ICC Publications.
National Fire Protection Association. (2023). NFPA 70 National Electrical Code. NFPA.
What States Allow ADU: A State-by-State Breakdown of Regulations. (n.d.). BuildGreenNH. https://buildgreennh.com/what-states-allow-adu/
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