State building permit guide
New Hampshire building permits — complete guide (2026)
New Hampshire has a mandatory statewide building code but a strong tradition of local control. Manchester and Nashua lead in permit volume. NH has no income or sales tax, keeping permit fees generally reasonable.
Avg cost: $150–$600
Processing: 1–5 weeks
~7,000 permits/year
10 counties
$150–$600Average permit cost
1–5 weeksProcessing time
~7,000Permits issued/year
Yes — 2023 state lawADU-friendly
New Hampshire passed an ADU law in 2023 (RSA 674:71-73) requiring all municipalities to allow at least one ADU on any single-family lot. This was a significant change — many NH towns previously prohibited ADUs. The frost depth in New Hampshire (48–60 inches) is among the deepest in the country and significantly affects foundation costs.
Permit costs by type — New Hampshire
| Permit type | Fee range | Processing time | Notes |
|---|---|---|---|
| Electrical | $100–$275 | 1–5 days | Licensed electrician required statewide |
| Plumbing | $90–$250 | 1–5 days | Licensed plumber required |
| HVAC / Mechanical | $100–$275 | 2–6 days | Oil heat conversion common |
| Roofing | $125–$350 | 1–4 days | Snow load design required statewide |
| New Construction | $600–$1,800 | 2–7 weeks | Rising costs due to population growth |
| Room Addition | $350–$950 | 2–5 weeks | Deep frost footings add cost |
| Deck / Patio | $150–$450 | 1–4 weeks | Frost depth 48–60 inches |
| ADU | $350–$900 | 2–5 weeks | 2023 law — municipalities must allow |
| Solar | $100–$275 | 1–5 days | Good net metering policy |
| Pool | $175–$500 | 1–4 weeks | Short season — permit still required |
How to get a building permit in New Hampshire
1
Find your town building department
New Hampshire has 234 municipalities. Many small towns share a building inspector. Contact your town office to find the right contact.
2
Check for new ADU rules
Under RSA 674:71, all NH municipalities must allow at least one ADU per single-family lot. If your town previously prohibited ADUs, they may now be required to allow them.
3
Licensed contractor requirement
NH requires licensed electricians, plumbers, and mechanical contractors for all permitted trade work.
4
Submit application — mostly paper
Most NH towns still use paper applications. Manchester and Nashua have online portals. Budget extra time for smaller town processing.
5
Inspections
NH inspectors cover wide geographic areas in rural areas. Schedule inspections well in advance — 1–2 week waits are common outside Manchester/Nashua.
Permit costs by county — top New Hampshire counties
Hillsborough (Manchester/Nashua) County
$175–$600
2–6 weeks
Rockingham (Derry/Portsmouth) County
$175–$575
2–5 weeks
Merrimack (Concord) County
$150–$500
1–5 weeks
Strafford (Dover/Durham) County
$150–$500
1–5 weeks
Grafton (Plymouth/Hanover) County
$125–$425
1–4 weeks
Carroll (Conway/Lakes Region) County
$125–$425
1–4 weeks
Frequently asked questions — New Hampshire permits
What is New Hampshire's 2023 ADU law?
RSA 674:71-73 requires all New Hampshire municipalities to allow at least one accessory dwelling unit on any single-family lot. Municipalities cannot require owner-occupancy, set parking requirements, or impose design standards stricter than the primary home.
What is the frost depth in New Hampshire?
New Hampshire's frost depth is 48–60 inches depending on location — one of the deepest in the country. This significantly increases foundation costs for decks, additions, and new construction.
Does New Hampshire have a state income tax?
NH has no income or sales tax. This affects the state's revenue model and keeps many fees — including permit fees — relatively reasonable compared to neighboring states.
Can NH homeowners do their own electrical work?
Yes. NH homeowners can do their own electrical work on their primary residence with a permit. Licensed electricians are required for all other work.
Data sources: US Census Bureau BPS 2024 · New Hampshire NH Office of Professional Licensure and Certification · Shovels.ai permit aggregator