ADUs are allowed in TrentonTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Trenton, NJ
Is your property eligible for an ADU?
# of Properties
27,565
Owner-occupied
44%
Zoning districts
23
Avg Home Value
$136,620
Median Lot Size
0.05 acres
Avg Income
$68,727
Residential Types:
27,565 housing units
2-3 Family
84%
Apts (4+ units)
1%
Other
15%
Zoning Districts:
31,714 parcels · 23 districts
RH-1
45%(14,377)
RM-1
25%(7,799)
RM-2
7%(2,212)
C-CC
7%(2,186)
Other
16%(5,140)
ADU Rules
What can you build in Trenton, NJ?
Trenton, NJ follows state and local rules for Accessory Dwelling Units. Here is a concise overview of the local rules.
Eligibility
- –Internal / Attached ADU: By Right
- –Detached ADU: By Right
Interior / Attached ADU Size Limits
- –Internal ADU (in-home apartment) maximum size cap of 800 sq ft.
- –Internal ADU (in-home apartment) maximum size of 40% of the primary dwelling’s floor area (uses gross building area if available, else habitable area).
Detached ADU Size Limits
- –Maximum detached ADU size of 800 sq ft (Trenton LDO §315-9.4.B.7).
- –Maximum detached ADU size is 40% of the primary dwelling floor area (uses HABITABLE_SQFT if provided, else GROSS_BUILDING_AREA_SQFT) (§315-9.4.B.8).
- –Detached accessory structure footprint cannot exceed principal building footprint; ADU floor area capped as principal footprint × ADU stories (§315-9.4.A.5).
Max Units
- –Detached single-family lot: 1 ADU (attached/internal or detached)
- –Duplex/multifamily: 0 ADUs
Owner Occupancy
- –Owner must occupy one dwelling unit on the property.
Parking
- –0 spaces/ADU; max tied to principal use (single-family has no max); citywide off-street parking has no minimum
ADU State Law
What can you build in New Jersey?
- –New Jersey does not have a statewide ADU mandate; ADU rules are set by individual municipalities.
- –Building/fire codes are set statewide, but whether an ADU is allowed is local zoning.
What's allowed on your lot?
These are the municipality-wide rules. What's allowed on a specific property also depends on state laws, setbacks, floor area ratio, lot coverage, environmental constraints, topography, and other property-specific factors. Search your address on FutureLot to see what's allowed on your property.
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ADU rules in other New Jersey municipalities
Rules change at the town line. Check the municipality your property is actually in.
Mercer County