Check Your State and Local Zoning Codes and Regulations
Zoning codes vary widely by location, and while they must adhere to state guidelines, local communities can tailor the regulations to their specific needs. The various ordinances and laws enacted by local or state governments cover a great deal of ADU use and construction, including their design, size, parking requirements, and the administration procedures around building them:
- Purpose of ADU: State and local regulations prioritize the maintenance and upkeep of ADUs, emphasizing that homeowners inhabit either the primary residence or the ADU.
- ADU Design: Different communities allow for detached ADUs, attached ADUs, or both ADU types. They might also require visual similarities between the ADU and the primary residence or other existing structures.
- ADU Size: State and local laws often restrict the ADU's total square footage, ensuring it remains a complementary unit to the primary dwelling.
- Parking: Due to the impact on parking space, some locales may require adequate parking space on the property before an ADU can be built.
- Administration: Obtaining approval for an ADU build hinges on state and local regulations. While some may only require standard building permit approval, others might demand special-use permit approval.
Understanding ADU Permit Applications
Depending on state and local regulations, constructing an ADU on your property can be done, but obtaining a permit is necessary. Homeowners must seek ADU approval, building permits, and other utility-related permissions in some states or face fines, insurance complications, and potential lawsuits or stop orders.
Securing an ADU building permit can demand a substantial investment of time and involves considerable amounts of paperwork. Engaging a general contractor can streamline this process, making it easier for homeowners.
Typically, the requirements for obtaining an ADU building permit include:
- Application form for a building permit
- Residential system development charge form
- Comprehensive construction plans
- Site plan (4 copies)
- Completed NSFR (Net Stable Funding Ratio) Intake Packet specifically for detached ADUs
Can I Build an ADU on My Property: Washington, Oregon, North California, Idaho
For homeowners in Washington, Oregon, North California, and Idaho considering a detached ADU on their property, here are some of the specific requirements:
Washington
In Washington, an ADU must not exceed 40% of the main house’s total floor area or be within 300-800 square feet, with a limit of two bedrooms, without special permission from the building official. Refer to the Model Accessory Dwelling Unit Ordinance Recommendations for greater details.
What is the New Washington ADU Law?
In urban growth areas, as detailed in the Growth Management Act, it’s mandated that lots meeting the minimum size required for the primary housing unit must allow for two Additional Dwelling Units (ADUs) alongside the principal unit.
Oregon
Oregon allows for ADU construction on your property, with guidelines outlining that the habitable gross floor area must not exceed 50% of the main house or 900 square feet, whichever is greater. Explore more standards in Chapter 17.80.
North California
In California, a detached ADU shouldn’t exceed 1,000 square feet and must have a maximum of two bedrooms for residential use. Refer to Chapter 16.79 for further specifications.
What is the New California ADU Law?
Recent statewide changes in 2023 have relaxed height restrictions, enabling constructions to exceed the previous 16-foot limit under specific circumstances.
Idaho
In Idaho, ADUs must be at most 750 square feet and should have only one bedroom. Explore the other particular standards for ADUs in section 17.06.100.
- 1 bed
- 1 bath
- 800 sq ft.
- 1 bed
- 1 bath
- 500 sq ft.
- 1 bed
- 1 bath
- 500 sq ft.
Building an ADU on Your Property
Constructing an ADU requires compliance with state and local standards to ensure safety and support community home values. It’s essential to have some working knowledge of the regulations and requirements, not only to help prevent potential lawsuits and fines but also to make a smoother building process overall. For guidance in navigating your local ADU regulations, contact a local HiLine Home Consultant for a consultation and begin your ADU journey.
