Trenton

1. Pre-application zoning verification (~7d)
   Confirm parcel is in Residence A/B/C district per TMC Article 4 zoning map; check overlay (Capitol District, historic Mill Hill, riverfront flood-zone). Trenton Division of Planning offers a $50 zoning-verification letter.
2. UCC construction permit application (~1d)
   Submit NJ DCA Construction Permit Application (UCC F100) to Trenton Division of Technical Services, 319 East State Street. Include site plan, floor plan, elevations, structural details, NJ-licensed architect/engineer seal, plus subcode technical sections (building, electrical, plumbing, fire).
3. Single-trade fast-track issuance (when applicable) (~2d)
   Single-trade-only ADU work (e.g., basement plumbing finish) issues within 48 hours per Trenton Technical Services policy.
4. Full plan review (when not single-trade) (~28d)
   20 working days from the construction inspector's acceptance for complete plan review across all four UCC subcodes. Approval/denial letter issued to design professional.
5. Tax-current certification (~3d)
   Before permit issuance, applicant must file Tax Collector certification that all municipal taxes and assessments are current per TMC Chapter 42.
6. Permit issuance and fee payment (~1d)
   Permit issues; UCC subcode fees, DCA training fee, and Trenton local surcharges due at issuance.
7. Construction inspections
   Footing, foundation, framing/rough MEP, insulation, final. Inspections requested via Trenton Technical Services 609-989-3550.
8. Certificate of occupancy (~5d)
   Final inspections cleared; CO issued; ADU eligible for occupancy and rental registration.

• Long-term rental: yes (TMC Chapter 315) Long-term rental of ADU permitted; rent control does NOT apply to ADUs at single-family principal-dwelling parcels.
• Short-term rental: with-restrictions (Trenton Municipal Code (rental registration)) Trenton has not adopted a dedicated STR ordinance as of 2026-04; STR-style rental of an ADU operates under the standard rental-registration regime.
  • Rental registration with Trenton Department of Inspections required
  • C/O reinspection required between tenants
  • STRs unregulated under dedicated ordinance; subject to standard rental rules
• Office rental: no TMC limits ADU to dwelling-unit use; commercial office tenancy not permitted.
• Home office: yes Home occupation permitted with TMC limits on signage, customer traffic, employees.
• Studio / workshop: yes Personal artist studio is a permitted accessory use.
• Agriculture: with-restrictions Limited urban agriculture / community gardens permitted; livestock generally prohibited within city limits.
• Relative support: yes Family-occupancy ADU explicitly permitted; commonly used for caregiver/in-law arrangements.

• NJHMFA First-Generation Down Payment Assistance — $15,000 (First-generation homebuyer; income-limited; can be paired with ADU purchase financing)
• Trenton Urban Enterprise Zone (UEZ) sales-tax reduction — Reduced 3.3125% sales tax on building materials purchased from UEZ-certified vendors (Construction within UEZ boundary; vendor must be UEZ-certified)

Staff: Construction Permit Counter (Permit Intake / Inspection Scheduling), Division of Planning (Zoning verification / Planning Board)

• Water: Trenton Water Works (TWW) · 30d connect · $2,800
• Sewer: Trenton Sewer Utility (treatment via Trenton Sewerage Authority / CCMUA) · 21d connect · $4,200
• Electric: PSE&G · 21d connect · $1,200 · separate meter required
• Gas: PSE&G · 30d connect · $1,500

Realistic total: best 7mo · typical 11mo · worst 17mo

Mercer County GC market is mid-depth (~260 licensed). Lead time eased somewhat post-2024 as Princeton-area discretionary projects slowed. Worst-case extended by Delaware River flood-zone special inspections.

Modular pathway NJ DCA Bureau of Homeowner Protection - Modular & Manufactured Housing · inspectors are rare with modular · 1 modular permits (last 24mo)

Trenton's narrow downtown streets and overhead utility lines limit module width; rear-yard placement on rowhouse parcels often requires crane access through alley or via demolition of adjacent garage.

State ADU loans:

• NJHMFA First-Time Homebuyer Mortgage Program (New Jersey Housing & Mortgage Finance Agency)
• NJHMFA First Generation DPA Program (NJHMFA) up to $15,000
• New Jersey Homeowner Assistance Fund (NJERMA) (NJ DCA)

Delaware River flood zone drives meaningful flood-insurance premium for parcels in SFHA; non-flood-zone parcels see modest delta. NJ admitted-carrier market remains stable.

Trenton is overwhelmingly fee-simple rowhouse / detached single-family without HOA. New Jersey law does NOT preempt HOA-ADU prohibitions, so the few condominium / townhouse associations may bar ADUs.

• historic-district — Mill Hill Historic District, Old Mill Hill, Trenton Capitol District, Cadwalader Heights · +30d · +10% cost
  Trenton Landmarks Commission review required for ADUs in designated historic districts; certificate of appropriateness needed for exterior alterations. (map)
• flood-zone — Delaware River SFHA Zone AE along Riverline / South Trenton; Assunpink Creek floodplain through Mill Hill / Trenton Central; Shabakunk Creek tributaries · +21d · +12% cost
  Finished-floor elevation 1 ft above BFE; flood vents on enclosed below-base areas; NJDEP Flood Hazard Area Permit may be required for parcels within 50 ft of regulated waters. (map)
• other — NJ State Capitol Complex viewshed and Capitol Park overlay · +14d · +4% cost
  Capitol-area parcels subject to height/massing review for state-house viewshed protection. (map)