- Max size800 sq ft
- Owner occupancyNot required
Princeton permits ADUs under specific conditions, opening up possibilities for homeowners looking to generate rental income or house family members. Whether you're considering an income-generating rental property, a dedicated space for extended family living, or a private guest house and workspace, understanding the local zoning rules is essential to moving forward with confidence. We've reviewed Princeton's zoning regulations in detail and outlined the key requirements below. Rules can change, so confirm details with the Princeton Planning Department or book a free consultation with our team before starting your project.
Status
- Adoption status
- Active — Princeton has had ADU regulations for several years; the most recent significant change was Ordinance #2020-16, which eliminated the owner occupancy requirement and permitted separate sale of the ADU
- Governing ordinance
- Princeton Municipal Code; Ordinance #2020-16 (most recent major amendment)
- Key differentiator
- Princeton uniquely has NO owner occupancy requirement and explicitly permits the ADU to be sold separately from the primary dwelling as a condominium
Eligibility
Where ADUs are allowed
- Zoning districts permitted
- All single-family residential districts: R-A, R-B, R-C, R-D, R-E, R-F, R-G, R-H
- Lot type / use restrictions
- Permitted as part of a primary dwelling or as a separate accessory structure on the same lot; side or rear yard location exclusively
- Minimum lot area required
- No minimum lot size requirement
- Limit per property
- Maximum of 1 ADU per lot
Types allowed
- Attached ADU (interior conversion — basement/attic)
- Yes
- Attached ADU (addition)
- Yes
- Detached ADU (new construction)
- Yes — as a separate accessory structure on the same lot
- Detached ADU (accessory structure conversion — e.g., garage)
- Yes
- Home occupation
- An ADU may also be used for residential and/or occupational purposes (home occupation); space is limited to residents solely; no exterior indication of home occupation is allowed
Size and placement
Size limits
- Maximum sq ft
- 800 sq ft or 25% of the total floor area of the primary dwelling unit, whichever is greater
- Accessibility exception
- If the ADU is handicapped accessible, an additional 5% of the total floor area may be added to either the primary dwelling or ADU (New Jersey's Barrier Free sub-code)
- Maximum height
- 20 ft or the height of the primary dwelling unit, whichever is less
- Maximum habitable rooms
- 3 habitable rooms per ADU
Setbacks
| Zone dimension | R4 Example |
|---|---|
| Front yard | 25 ft |
| Combined side yards | 20 ft |
| Smaller side yard | 8 ft |
| Rear yard | 35 ft |
- Location restriction
- ADU (as a detached structure) must be located in the side or rear yard exclusively; not in the front yard
- Specific setback requirements
- The specific setback and lot coverage requirements of the district apply
Rules for use
Parking
- ADU with 2 habitable rooms or fewer
- No additional off-street parking required
- ADU with 3 habitable rooms
- 1 additional off-street parking space required
Owner occupancy
- Required
- No — Ordinance #2020-16 eliminated the owner occupancy requirement. Neither the property owner nor any resident is required to occupy the primary dwelling
- Separate sale permitted
- The property owner may sell both the primary dwelling and the ADU to separate people, making it a condominium-style arrangement
Rental use
- Short-term rental
- Not specifically prohibited by ADU ordinance; however, standard Princeton STR regulations apply
- Long-term rental
- Permitted
- Separate sale/condominium
- Permitted under Ordinance #2020-16 — the ADU can be sold as a separate condominium unit from the primary dwelling
How to apply in Princeton
- Zoning approval
- Required from Princeton Zoning Office
- Building permit
- Required; applicant typically works with a civil engineer to obtain municipal approvals
- Contact
- Princeton Department of Planning, 400 Witherspoon Street, Princeton, NJ 08540
Recent and pending changes
- Ordinance #2020-16Eliminated owner occupancy requirement and introduced the separate condominium sale option; this was a significant liberalization from prior ordinance
Important details
- No owner occupancy + separate sale: Princeton's most distinctive provision — Uniquely, Princeton allows the ADU to be sold as a condominium separate from the primary dwelling, and neither owner is required to live on the property
- Home occupation permitted: The ADU may be used for both residential and occupational purposes (home office, studio, etc.) as long as there is no exterior indication
- Survey requirement: Applicants need a stamped survey less than 10 years old as part of the application package
- Accessibility incentive: Handicapped-accessible ADUs can exceed the standard 25%/800 sq ft cap by an additional 5% of the total floor area
Frequently asked questions
Do I need to own my home to build an ADU in Princeton under New Jersey's new law?
No. Princeton's ADU ordinance allows both owner-occupied and separate ownership. This means you can even sell the ADU as a separate unit from the primary residence, enabling creative ownership structures and making ADUs more accessible to first-time homebuyers.
What's the maximum size for an ADU in Princeton, and are there income restrictions?
Standard ADUs are limited to 800 square feet or 25 percent of the principal dwelling's floor area, whichever is greater. However, if the ADU is restricted to low- and moderate-income occupancy, it can be up to 1,000 square feet or 30 percent of the principal dwelling. Accessible units receive a 5 percent floor area bonus.
Can I use my Princeton home and ADU for short-term rentals like Airbnb?
Yes, but with conditions. Your primary residence must be your principal residence, and you must obtain a short-term rental permit. Permits cost $200 for initial registration and $100 annually, with $500,000 minimum liability insurance required. Only one ADU is allowed per lot.
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Last reviewed 2026-04-26. Local rules can change — verify the latest details with the Princeton planning department, or book a free consultation with our team before starting your project. This page is informational and is not legal advice.