Building permits, zoning and septic rules in Merrimack County, New Hampshire

At a glance

Building permit

Required for covered construction through the applicable local process¹

Zoning

Rules vary by municipality and zoning district²

Septic

Approved statewide by NHDES, not the county³

RV living

Campgrounds allow temporary stays only; a year-round site must meet the state's single-family septic standard⁵

Accessory dwelling unit

One attached or detached unit is allowed where single-family homes are permitted, subject to local and septic conditions⁶

Owner-builder exemption

Unconfirmed for Merrimack County; ask your town's building office directly⁷

Wells

No universal state well-construction permit; the contractor must file a completion record within 90 days⁸

Who to call

Contact details are copied from each office’s official page and were checked against it on October 9, 2026.

Do you need a building permit in Merrimack County, New Hampshire?

New Hampshire's building code applies throughout Merrimack County, and covered construction, remodeling or related work requires a building permit⁴¹. Where a municipality has adopted an enforcement mechanism, the permit follows that municipality's process¹. The building official generally must decide a completed application within 30 days; the period is 60 days for nonresidential applications or residential applications covering more than 10 dwelling units⁹. Work performed under an issued permit requires inspections at the appropriate stages and before it is concealed¹⁰. A municipality may also require a certificate of occupancy, so confirm that requirement with the town before planning a move-in date¹¹.

Who issues building permits in Merrimack County, and how do you reach them?

Building permits in Merrimack County are issued by each city or town, not by the county, so begin with the city or town where the parcel lies²¹. Inside Concord, the Code Administration Division at 37 Green Street handles building, housing and health or licensing permits and can be reached at 603-225-8580¹². Concord's zoning administration is in the Planning Division at 41 Green Street, reachable at 603-225-8515¹²¹³. The state fire marshal's direct permitting, inspections and certificates of occupancy cover buildings owned by New Hampshire, the community college system or the university system¹⁴. Merrimack County's Administration Office at 333 Daniel Webster Highway in Boscawen, (603) 796-6800, is a general county contact if you are unsure which municipality or agency serves the parcel¹⁵.

Does Merrimack County have zoning?

Zoning approval in Merrimack County comes from each city or town, and rules vary by municipality and district; local rules may govern building size and height, lot size, yards, open space, density and land use². Concord's Planning Division reviews applications against its zoning, site-plan and subdivision regulations¹³. New Hampshire municipalities must allow one attached or detached accessory dwelling unit as a matter of right in districts permitting single-family homes, while retaining authority over owner occupancy, parking, aesthetics, septic and other statutory conditions⁶. A municipality may not restrict an accessory dwelling unit below 750 square feet and may cap it at 950 square feet unless it authorizes more⁶. We could not confirm one countywide schedule for setbacks, minimum lot size, lot coverage or building height, so obtain the parcel's zoning district and dimensional table from its municipality before designing a home.

How do septic permits work in Merrimack County?

Septic permits in Merrimack County, including inside Concord and every other town, are approved by NHDES rather than the county or the municipal building office, although local requirements may apply before an application reaches the department³. Prior approval of the plans and specifications is required before constructing a sewage-discharging building or a sewage or waste-disposal system¹⁶. NHDES issues construction approval after the state and, when required, the municipality approve the proposed plans¹⁷. Approval to operate follows final inspection, and the system cannot be covered or used beforehand¹⁸. The NHDES application fee is $450¹⁷. Only about 3% of county soils are rated without severe limits for a conventional drain field, so make a site evaluation an early contingency rather than assuming a standard field will fit¹⁹. Municipal subdivision review may also apply where the town has authorized its planning board to regulate subdivisions²⁰.

Can you live in an RV or tiny home on your land in Merrimack County?

We could not confirm a countywide rule for living in an RV. State law exempts only occasional RV use of a parcel for no more than 7 days in a calendar year, with a statement of compliance filed with the municipality and local zoning and health rules still enforceable²¹. For anything longer, ask the parcel's municipality about occupancy, camping and zoning before relying on an RV as temporary or permanent housing. A municipality may permit a qualifying tiny house on an individual lot where single-family homes are allowed or as an accessory dwelling unit, but all local land-use, drinking-water and wastewater requirements still apply²². For this rule, a qualifying tiny house has no more than 600 square feet excluding lofts, complies with the state building code's tiny-home provisions and sits on a stable ground surface or foundation²². Local zoning still controls the parcel's district and dimensional standards². One attached or detached accessory dwelling unit must be allowed where single-family homes are permitted, subject to the statutory local and septic conditions⁶.

How do you build a home in Merrimack County, step by step?

1. Identify the parcel's municipality and obtain its zoning district, allowed-use rules and dimensional table².
2. Ask the local building official for the building permit application and local fee schedule; covered construction requires a permit through the applicable process¹.
3. Arrange the septic site work and obtain the NHDES septic approval of the plans before constructing a sewage-discharging building or system¹⁶.
4. Submit a complete building application; the general decision period is 30 days, or 60 days for nonresidential applications and residential applications covering more than 10 dwelling units⁹.
5. Request building inspections at the required stages and before concealing work¹⁰.
6. Obtain final septic inspection and approval before covering or operating the system¹⁸.
7. Ask whether the municipality requires a certificate of occupancy before moving in¹¹.

What should you check before buying land in Merrimack County, New Hampshire?

Soils and septic: only about 3% of county soils are rated without severe limits for a conventional drain field, so make buildability and septic approval purchase contingencies¹⁹¹⁶. Zoning: allowed uses, setbacks, lot sizes and other dimensional standards depend on the municipality and district². Floodplain: municipalities may adopt separate or zoning-based floodplain ordinances, but we could not confirm every current local ordinance; ask the municipality and check the parcel's mapped flood status²³. Terrain: roughly 76% of Merrimack County land has a slope of 15% or less, while about 86% is wooded²⁴²⁵. Location: population density is about 168 people per square mile, and the nearest city of 100,000 or more is about 25 miles from the county center in a straight line²⁶²⁷. Taxes: the effective property tax rate is about 2%, and the median annual property tax bill is about $6,617²⁸²⁹.

Watch-outs

• Concord moved all zoning administration, including Zoning Board of Adjustment applications, from the Code Administration Division to the Planning Division effective September 30, 2024; use the Planning Division for any zoning question in the county seat¹²¹³.
• NHDES raised its statewide septic (sewage disposal) permit application fee from $300 to $450 effective July 1, 2025; budget for the current amount, not an older figure you may see elsewhere¹⁷.
• Building permits for covered construction follow the applicable local process, and municipal administration varies; contact the parcel's town before starting work¹².
• Merrimack County's owner-builder exemption status is unconfirmed; do not assume one exists without checking with your town's building office⁷.
• A tiny house is not automatically exempt from land-use rules: the municipality may allow a qualifying tiny house only where the state conditions and all applicable local requirements are met²².

Sources

1. RSA 155-A:4 Permit Required, quoted and re-checked
2. RSA 674:16 Grant of Power, quoted and re-checked
3. RSA 485-A:32 Prior Approval; Permits, quoted and re-checked
4. Chapter 155-A New Hampshire Building Code, quoted and re-checked
5. Chapter 216-I Recreational Campgrounds and Camping Parks (New Hampshire statewide rule), quoted and re-checked
6. RSA 674:72 Accessory Dwelling Units, quoted and re-checked
7. RSA 155-A:4 — Permit Required (2026 county census)
8. RSA 482-B:10 Record of Wells; Monitoring Wells (New Hampshire statewide rule), quoted and re-checked
9. RSA 155-A:4 Permit Required, quoted and re-checked
10. gc.nh.gov, quoted and re-checked
11. Chapter 155-A New Hampshire Building Code, quoted and re-checked
12. City of Concord Code Administration Division (concordnh.gov)
13. City of Concord Planning Division (concordnh.gov)
14. Section 155-A:2 State Building Code, quoted and re-checked
15. Merrimack County Administration Office (merrimackcounty.net)
16. RSA 485-A:32 Prior Approval; Permits, quoted and re-checked
17. New Hampshire Department of Environmental Services, Subsurface Systems Bureau (des.nh.gov)
18. Env-Wq 1000 Subsurface Disposal Systems, quoted and re-checked
19. Share of soils USDA rates "not limited" for a conventional septic drain field (SSURGO). A strict rating: the median county is about 6% and a tenth of counties are 0%, so a low figure means most lots need a site evaluation or an engineered system, not that septic is impossible. Cite it only with that caveat: Bolthole Index county data
20. Chapter 674 Local Land Use Planning and Regulatory Powers, quoted and re-checked
21. RSA 216-I:13 Partial Exception for Certain Uses of Recreational Vehicles, quoted and re-checked
22. RSA 674:82 Definitions, quoted and re-checked
23. RSA 674:56 Flood Hazards, quoted and re-checked
24. Share of land at 15% slope or less: Bolthole Index county data
25. Wooded share of land: Bolthole Index county data
26. Population density: Bolthole Index county data
27. Straight-line distance from the county center to the nearest city of 100,000+ people: Bolthole Index county data
28. Effective property tax rate: Bolthole Index county data
29. Median property tax bill: Bolthole Index county data

Written October 9, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.