Zoning & Size Limits
| Requirement | Princeton, NJ | Jersey City, NJ |
|---|
| Allowed Zones | All residential districts where single-family dwellings are | R-1, R-2, RH-1 and RH-2 zones (check the Jersey City Interac |
| Max Size (Detached) | 800 sq ft or 25% of the principal dwelling's total floor area, whichever is greater; +5% total floor area if the ADU is fully accessible under NJ's Barrier Free subcode; 1,000 sq ft or 30% if deed-restricted to low/moderate-income occupancy (Ord. 2024-32) | No square-footage cap — size is limited by the 18 ft/2-story height limit, setbacks and lot coverage (R-1: maximum lot coverage increases by an additional 5% for an ADU; R-2: 80% lot coverage; RH-1: 75% lot / 55% building coverage; RH-2: 75% lot coverage) |
| Max Size (Attached) | Same standard as detached — 800 sq ft or 25% of principal floor area, whichever is greater; attached ADUs must use the same exterior materials and colors as the main house | Not permitted — all Jersey City ADUs must be detached from the principal structure; attached/ground-floor garage conversions are a separate conditional use (LDO §345-41 G.1, R-1 zone, Planning Board approval, driveway and curb cut must be removed) |
| Max Height | Detached ADUs follow the accessory-structure bulk | 18 feet or 2 stories (18 feet in RH-1) |
| Parking Required | No additional parking for ADUs with 2 habitable rooms; 1 add | ADUs are exempt from parking requirements (in R-2, follow R- |
| Owner Occupancy | Not required — Ordinance 2020-16 expressly eliminated Prince | No owner-occupancy requirement appears in the LDO ADU standa |
Setback Requirements
| Setback | Princeton, NJ | Jersey City, NJ |
|---|
| Rear Setback | Per the accessory-structure setbacks of the underlying district — confirm with the Princeton Planning Department; detached ADUs must be at least 5 ft from the habitable portion of the main house | R-1: 2 ft (per building code); R-2: 3 ft; RH-1 and RH-2: none |
| Side Setback | Per the accessory-structure setbacks of the underlying district — confirm with the Princeton Planning Department | R-1: 2 ft; R-2: 3 ft; RH-1 and RH-2: 2 ft |
| Front Setback | No separate street-facing external entrance is all | ADU sits behind the principal structure; corner, c |
Permits & Timeline
| Detail | Princeton, NJ | Jersey City, NJ |
|---|
| Permit Timeline | Confirm with the Princeton Zoning Office — no published ADU-specific timeline | Confirm with the Division of Zoning — no published ADU-specific timeline |
| Permit Fees | Confirm with the Princeton Zoning Office and Building Department — zoning permit plus UCC construction permit fees scale with project value | Confirm with the Division of Zoning and Division of Construction Code Official — no published ADU fee schedule |
| Impact Fees | No California-style ADU impact fees; sewer connection charge | No California-style ADU impact fees; sewer/water connection |
| Pre-Approved Plans | None offered as of July 2026 | None offered as of July 2026 |
Construction Costs
| Cost | Princeton, NJ | Jersey City, NJ |
|---|
| Avg Build Cost | $180,000-$350,000 | $150,000-$300,000 |
| Cost Per Sq Ft | $250-$400 | $200-$350 |
| Garage Conversion | $70,000-$150,000 | $60,000-$150,000 (detached garages only — attached-garage conversions are a separate conditional-use dwelling unit, not an ADU) |
| Prefab ADU | $130,000-$260,000 installed | $120,000-$250,000 installed (tight urban lot access can add crane/site costs) |
Rental Income Potential
| Rental | Princeton, NJ | Jersey City, NJ |
|---|
| 1BR Avg Rent | $2,400-$2,900/mo | $2,900-$3,400/mo |
| 2BR Avg Rent | $3,000-$3,500/mo | $3,900-$4,600/mo |
| Short-Term Rentals | The ADU must be used 'only for residential purposes for one | Heavily restricted — Jersey City's short-term rental ordinan |
| Est. ROI | 6-9% gross annual return (long-term rental, before taxes and financing) | 8-12% gross annual return (long-term rental, before taxes and financing) |
Which City Is Better for ADUs?
Princeton scores 8/10 while Jersey City scores 7/10 on our ADU-friendliness index.
Princeton edges ahead overall. Both cities offer viable ADU development opportunities — the best choice depends on your specific property, budget, and goals.
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