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Zoning Guide

Merrimack, NH Zoning Regulations & Building Permits

Data-only stub — facts unverified locally. Confirm with the planning department before relying on details.
Last updated: Verified:

What we have on file vs. what to verify locally

We don't have editor-verified zoning prose for Merrimackyet. Here's the structured data we do have, and the highest-leverage steps to confirm specifics for your parcel.

What we have on file

Population:
26,632
County:
Hillsborough County
State building code:
NH State Building Code (based on 2018 IBC)(statewide default)
State ADU law:
Yes — New Hampshire RSA 674:71-73 (enacted by SB 146, signed March 2016) requires municipalities that adopt zoning to allow at least one accessory dwelling unit as a matter of right or by conditional use permit/special exception in all zoning districts that permit single-family dwellings. HB 1291 (2024), which would have expanded this to two ADUs by right, passed the House but was killed in the Senate.
FEMA flood map:
Search flood zones
Planning department:
Merrimack Community Development

Verify these locally

  • Call the Merrimack Community Development: (603) 424-2331
  • Check FEMA flood zone for your parcel — flood-zone status changes setbacks, foundation requirements, and insurance.
  • Check your HOA CC&Rs and recorded deed restrictions — they are common in Merrimack and frequently restrict ADUs, fences, and exterior changes beyond what zoning allows.

Key Zoning Facts

Planning Department
Merrimack Community Development(603) 424-2331
Building Code Edition
NH State Building Code (IBC/IRC based)
ADUs Allowed
Yes

Merrimack Zoning Overview

Merrimack is a town in Hillsborough County, New Hampshire, with a population of approximately 26,632 (2020 Census). Located in southern New Hampshire along the Merrimack River, the town manages land use and development through its zoning ordinance, administered by Merrimack Community Development.

Merrimack's zoning ordinance divides the town into several districts, including two residential zones, two commercial zones, and an industrial zone. The R district requires 40,000 sq ft minimum lots, while R-1 requires 20,000 sq ft.

Key Zoning Districts

Merrimack's primary residential zoning districts include:

  • R (Residential) — Minimum 40,000 sq ft lots with 40 ft front, 20 ft side, and 30 ft rear setbacks. Maximum height of 35 ft.
  • R-1 (Residential) — Minimum 20,000 sq ft lots with 30 ft front, 15 ft side, and 20 ft rear setbacks. Maximum height of 35 ft.

Commercial and industrial districts include:

  • C (Commercial) — General commercial district for retail, office, and service uses
  • C-1 (Highway Commercial) — Highway-oriented commercial district for larger-scale retail and services
  • I-1 (Industrial) — Manufacturing, warehousing, and related industrial uses

ADU Regulations (Accessory Dwelling Units)

New Hampshire state law (RSA 674:72-73) requires all municipalities to allow ADUs (Accessory Dwelling Units) as a matter of right on any property with a single-family dwelling. Merrimack must comply with this state mandate. Key points:

  • One ADU is permitted per single-family lot
  • The ADU may be attached to or detached from the primary dwelling (subject to local standards)
  • Municipalities cannot prohibit ADUs but may adopt reasonable regulations regarding size, parking, and other dimensional standards
  • Contact Merrimack Community Development for the town's specific ADU application requirements and any local dimensional standards

Building Code

Merrimack follows the NH State Building Code (RSA 155-A), which is based on the International Building Code (IBC) and International Residential Code (IRC). All construction must comply with the state building code.

Development Process

Development in Merrimack generally requires obtaining the appropriate permits from the town's planning and building departments. The process typically involves:

  1. Zoning Verification — Confirm that your proposed use is permitted in the applicable zoning district
  2. Site Plan Review — For commercial, multi-family, and certain other projects, submit a site plan to the Planning Board
  3. Building Permit — Apply for a building permit with construction documents
  4. Inspections — Schedule required inspections during construction
  5. Certificate of Occupancy — Obtain final approval before occupying the structure

For projects that do not conform to existing zoning, property owners may need to seek a variance or special exception from the Merrimack Zoning Board of Adjustment (ZBA).

Key Considerations

Before starting any development project in Merrimack, property owners should:

  • Verify the zoning classification of their property
  • Review setback, height, and lot coverage requirements for the applicable district
  • Check for any overlay districts or special regulations
  • Determine if the property is in a flood zone using FEMA's flood map service
  • Confirm whether HOA covenants or deed restrictions apply
  • Contact Merrimack Community Development at (603) 424-2331 for pre-application guidance

Disclaimer: This guide provides general information about zoning in Merrimack, NH and should not be relied upon as legal advice. Zoning codes are subject to change. Always verify current regulations with Merrimack Community Development before making development decisions.

Regulatory Layers That Apply in Merrimack

Your property is subject to ALL of these regulatory layers. Each one can impose additional requirements beyond the others.

Federal

State — New Hampshire

  • Building Code: NH State Building Code (RSA 155-A)
  • State ADU Override: Yes (NH RSA 674:72-73 requires municipalities to allow ADUs)
View New Hampshire zoning overview

County — Hillsborough County

    City / Municipal

    The city's zoning ordinance, building codes, and local permits form the primary layer of land-use regulation for your property.

    Overlay Districts

    No overlay districts identified.

    Private Restrictions

    • HOA / CC&Rs common: Yes
    • Check HOA CC&Rs and deed restrictions for additional requirements.

    Statewide Context (New Hampshire)

    Local data for Merrimack is limited. The following state-level facts apply across New Hampshire and are inherited by this page until city-specific details are verified.

    State Building Code
    NH State Building Code (based on 2018 IBC)
    State ADU Preemption
    Yes — state law overrides local rules
    Coastal Zone
    Yes
    Wildfire Zones
    No

    ADU Rules in Merrimack

    ADUs:Allowed(statewide context — not city-specific)

    State law (statewide context, not city-specific):

    New Hampshire RSA 674:71-73 (enacted by SB 146, signed March 2016) requires municipalities that adopt zoning to allow at least one accessory dwelling unit as a matter of right or by conditional use permit/special exception in all zoning districts that permit single-family dwellings. HB 1291 (2024), which would have expanded this to two ADUs by right, passed the House but was killed in the Senate.

    Source (New Hampshire)

    For local size, setback, and parking specifics, contact the Merrimack Community Development.

    Full ADU rules for Merrimack →

    Permit Costs & Timelines

    Permit Costs & Timelines

    Specific permit fee schedules for Merrimack are available from the local planning department. Fees vary based on project type, scope, and valuation.

    Check Merrimack permit fees →

    Official Sources

    City-specific

    Town of Merrimackmerrimacknh.govOfficial source