Understand Setback Requirements
Setbacks determine how close to property lines you can build. For ADUs, setback rules are often more lenient than for main houses—some cities even allow building right up to the property line in certain situations.
Quick Summary
Typical rear setback
4-5 feet
Typical side setback
4-5 feet
Reduced setback
Some allow 0 ft
Types of Setbacks
Rear Setback
Distance from the back property line. This is where most detached ADUs are built.
- • Standard: 5-15 feet (main houses)
- • ADU-specific: Often reduced to 4-5 feet
- • Some cities: 0 feet for single-story ADUs
Side Setback
Distance from side property lines. Applies to both sides of the ADU.
- • Standard: 5-10 feet (main houses)
- • ADU-specific: Often 4-5 feet
- • Adjacent to alley: Sometimes 0 feet allowed
Front Setback
Distance from street. ADUs are rarely allowed in front setbacks.
- • ADUs usually prohibited in front yard
- • Exception: Corner lots may use side-street setback
- • Attached ADUs follow main house setback
Setback from Main House
Some codes require minimum separation between ADU and primary residence.
- • Typical: 6-10 feet between structures
- • Fire codes may require more for certain construction
- • Attached ADUs: No separation needed
Typical ADU Setback Requirements
| Setback Type | Traditional | ADU-Friendly |
|---|---|---|
| Rear | 15-25 ft | 4-5 ft |
| Side | 5-10 ft | 4-5 ft |
| Side (alley) | 5 ft | 0 ft |
| From main house | 10 ft | 6 ft or none |
* Requirements vary significantly by jurisdiction. Always verify with your local planning department.
How State Laws Affect Setbacks
Several states have passed laws limiting how much local governments can restrict ADU setbacks:
California
State law limits rear and side setbacks to 4 feet maximum for ADUs. Local governments cannot require more. Zero-foot setbacks allowed for garage conversions.
Oregon
Recent laws require cities to allow reasonable setbacks for ADUs. Many cities have adopted 5-foot minimums for rear and sides.
Washington
New laws prevent cities from requiring setbacks greater than those for other accessory structures. Effectively 5-foot setbacks in most cities.
Special Setback Considerations
Two-Story ADUs
Second stories often require greater setbacks than single-story ADUs. Some jurisdictions require 10+ feet for upper floors or don't allow two-story ADUs near property lines at all.
Eave Overhangs
Roof eaves may be allowed to project into setbacks (typically 2-3 feet) without counting against the setback. This can add valuable square footage. Check your local rules.
Corner Lots
Corner lots have two "front" setbacks (street-facing sides). This can limit where you can place an ADU but may also provide more options than interior lots.
Easements
Utility easements, drainage easements, or access easements create additional no-build zones beyond standard setbacks. Check your property survey for easement locations.
Frequently Asked Questions
Can I get a variance for reduced setbacks?
Possibly, but variances are difficult and expensive ($1,000-$5,000+). With ADU-friendly laws in many states, you often don't need one. Check if standard ADU rules already give you what you need before pursuing a variance.
What if my neighbor's fence isn't on the property line?
Setbacks are measured from the legal property line, not fences. Get a survey if uncertain. Building based on a fence location could result in required demolition if the fence is in the wrong place.
Do decks and patios require setbacks?
Rules vary. Covered structures usually do. Uncovered decks under 30" high often don't. Ground-level patios typically don't need setbacks. Check your local code.
Ready for the Next Step?
After understanding setbacks, check height limit restrictions—another key factor in determining what size ADU you can build.