Hamilton, NJ Accessory Structures: ADU Impact Fees (2026)
Key Facts
- Fee rate
- 1.5% of increased equalized assessed value
- Trigger
- Adding an ADU to an existing home
- Collection
- 50% at building permit, 50% at CO
- Appeal body
- Mercer County Board of Taxation
- Key exemptions
- Affordable housing, nonprofits, government
- State authority
- N.J.S.A. 40:55D-8.1 through 8.7
Summary
Adding an accessory dwelling unit to an existing home in Hamilton triggers the Township's affordable housing development fee. Section 550-167D(1)(a) sets the fee at 1.5% of the increase in the property's equalized assessed value caused by the new unit, collected on the same schedule as other residential development fees.
Within all zone districts, all residential developers, except for developers of the types of developments specifically exempted below and developers of developments that include affordable housing, shall pay a fee of 1.5% of the equalized assessed value for all new residential development provided no increased density is permitted. Development fees shall also be imposed and collected when an additional dwelling unit is added to an existing residential structure; in such cases, the fee shall be calculated based on the increase in the equalized assessed value of the property due to the additional dwelling unit.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4984352; v35 updated 2026-06-16; through 06-16-2026).
Full Breakdown
Hamilton's development fee ordinance, added 4-2-2019 by Ord. No. 19-013 and amended 3-10-2026 by Ord. No. A. 7) to fund very low-, low- and moderate-income housing under a court- or Division-approved Spending Plan. 5% of equalized assessed value, and § 550-167D(1)(a) specifically extends that fee to an additional dwelling unit added to an existing residential structure, calculated only on the increase in equalized assessed value the ADU creates. Fees are collected in two installments under § 550-167E(1)(i): 50% when the building permit is issued and the balance when the certificate of occupancy is issued, once the Tax Assessor confirms the final assessed value increase.
Exemptions under § 550-167D(1)(b) cover affordable housing developments, developments with preliminary/final approval predating the fee ordinance, repairs or reconstruction costing less than 50% of the structure's market value, nonprofit 501(c)(3) housing providers, and government projects. A developer may challenge the fee before the Mercer County Board of Taxation under § 550-167E(2)(a), with collected funds held in an interest-bearing escrow account pending the outcome.
Violations & Fines
There is no separate criminal penalty; the development fee operates as a permit condition. The Construction Official will not finalize the certificate of occupancy for the added dwelling unit until the Tax Assessor confirms the increase in equalized assessed value and the remaining balance of the fee is paid, per § 550-167E(1)(i). If a homeowner disputes the fee, § 550-167E(2)(a) requires the disputed amount to sit in an interest-bearing escrow account while the County Board of Taxation, and on further appeal the New Jersey Tax Court, decides the challenge.
Frequently Asked Questions
Does building an ADU in Hamilton cost extra in fees?
When is the ADU development fee paid?
Can a homeowner dispute the ADU fee?
Sources & Official References
Other rules in Hamilton
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