ADU Pass
Franklin
ADU Pass helps homeowners in Franklin, Merrimack County, New Hampshire navigate the permit paperwork for building an accessory dwelling unit. This area covers 1 ZIP code.
Map
ADU details
ADU legality: allowed
New Hampshire preempts most local ADU restrictions. Franklin permits ADUs by right in single-family zones per its zoning ordinance.
Cost scenarios
| Scenario | Sq ft | Permit | Build | Total |
|---|---|---|---|---|
| minimum | 150 | $2,400 | $42,750 | $45,150 |
| 600 | 600 | $2,400 | $171,000 | $173,400 |
| midpoint | 675 | $2,400 | $192,375 | $194,775 |
| maximum | 1,200 | $2,400 | $342,000 | $344,400 |
Fee breakdown
Viability (permitted uses)
- Long-term rental: yes Long-term rental of ADU explicitly permitted; New Hampshire owner-occupancy preemption (where applicable) makes ADU eligible for full landlord-tenant treatment.
- Short-term rental: with-restrictions STR rules vary by city. Franklin regulates STRs separately from ADU permitting; check local STR ordinance and HOA covenants.
- Office rental: with-restrictions Detached office rental requires home occupation permit or rezoning.
- Home office: yes Home occupation permitted with restrictions on signage and customer traffic.
- Studio / workshop: yes Personal artist studio is a permitted accessory use.
- Agriculture: with-restrictions Limited urban agriculture permitted in residential zones; livestock varies by district.
- Relative support: yes Family-occupancy ADU explicitly permitted in single-family zones.
Utilities
- Water: Franklin Water Utility · 21d connect · $4,500
- Sewer: Franklin Sewer / Wastewater · 21d connect · $5,500
- Electric: Franklin Electric Utility · 14d connect · $1,800
- Gas: Franklin Gas Utility · 21d connect · $1,500
Property values & taxes
Construction timeline
Realistic total: best 7mo · typical 11mo · worst 17mo
Financing
State ADU loans:
Insurance impact
HOA prevalence & preemption
New Hampshire has no HOA-ADU preemption; HOA covenants restricting ADUs are enforceable.
Technical envelope (climate & building code)
Climate & energy code
Building code
Amendments:
- Amendment
- Amendment
Legal history (timeline)
Current ordinance: City of Franklin Municipal Code — Accessory Dwelling Units, adopted 2020-01-01, last amended 2024-04-01
- 2024-01-01 — City of Franklin ADU code refresh (city-ordinance)
Conforming local-code amendments aligning with current New Hampshire accessory-dwelling framework.
Effect: Codified by-right ADU standards consistent with state law and local zoning.
New Hampshire state — ADU law and programs
State ADU law
New Hampshire has long-standing statewide ADU preemption originally enacted in 2016 (SB 146 / RSA 674:71-73, effective 2017-06-01) and substantially expanded in 2025 by HB 577 (Chapter 197, Laws of 2025), signed by Governor Ayotte 2025-07-15 and effective 2025-07-01. Under the original 2016 law, every NH municipality with a single-family residential zone must allow at least one ATTACHED ADU by right (within or attached to the primary single-family dwelling). HB 577 expanded the mandate so municipalities must ALSO permit at least one DETACHED ADU per single-family lot, redefined ADU as 'located on a lot containing a single-family dwelling' (rather than 'within or attached to'), and required that municipalities allow ADUs to be created from existing structures including detached garages even where the existing structure violates current dimensional requirements for setbacks or lot coverage. HB 577 set ADU size: ordinances may not limit an ADU to less than 750 sq ft, and may not exceed 950 sq ft unless the municipality authorizes a larger size. Cities may apply otherwise-applicable RSA 674:72 IV-IX requirements (state building/fire code, public-health, septic). New Hampshire is one of the strongest ADU-preemption regimes in the country.
State financing programs
New Hampshire Housing Finance Authority (NHHFA, dba 'New Hampshire Housing'), a quasi-governmental authority operating under RSA Chapter 204-C, does not operate a stand-alone homeowner ADU loan or grant product as of 2026-04-26 — but the agency has been the country's most active state HFA in writing concrete ADU policy and program models. The April 2023 NHHFA report 'Policy and Program Models for Creating Accessory Dwelling Units in New Hampshire' lays out the state's current toolset and gaps. ADU construction can be financed through NHHFA's general homeowner programs (Home Flex Plus first-mortgage product with up to 4% non-repayable cash assistance, Home First with up to $10,000 in down-payment assistance) when the underlying primary-residence purchase or refinance qualifies. The InvestNH Housing Opportunity Planning (HOP) grants under InvestNH provided $30M+ in capital and an additional $2.9M in 2024 for municipal planning consultants — supporting cities to update zoning to comply with HB 577 and similar reforms. None of this is a per-ADU homeowner subsidy; the Granite State Homeowner Repair Loan and Septic Loan programs occasionally finance ADU-adjacent work.
State housing programs
New Hampshire's ADU programmatic posture pairs the strong RSA 674:71-73 / HB 577 preemption framework with the NHHFA-led InvestNH Housing Opportunity Planning grant program (≈$30M in capital plus $2.9M FY2024 expansion) helping municipalities update their zoning and master plans to comply. NHHFA's New Hampshire Housing Toolbox (https://nhhousingtoolbox.org/) hosts a model ADU ordinance, sample architectural drawings, and a homeowner-facing ADU resource page. The state does not operate a centralized pre-approved ADU plan catalog (e.g., a CalHFA-style design library), nor a per-ADU rebate program. The NH Office of Energy and Planning (within DBEDC / Department of Business and Economic Affairs) publishes 'Planning for Accessory Dwellings' guidance for local code amendments. Impact-fee waivers are NOT statutorily mandated; ordinance authority for fees remains with municipalities subject to the RSA 674:71-73 framework.
Federal (United States) — ADU-relevant rules and programs
Federal ADU law
The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.
Federal financing programs
Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.
Federal tax credits
There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.
Federal housing programs
HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.
ZIP Code
- 03235
Post Office
- 65 Franklin St, 03235