Portsmouth Zoning Overview

Portsmouth is a historic coastal city in Rockingham County, New Hampshire, with a population of approximately 22,158 (2020 Census). Located on the seacoast at the mouth of the Piscataqua River, Portsmouth is known for its historic downtown, maritime heritage, and vibrant cultural scene. Land use and development are regulated through the city's zoning ordinance, administered by the Portsmouth Planning Department.

Portsmouth's zoning ordinance divides the city into multiple districts, including several residential zones ranging from Single-Family A (SRA) with 15,000 sq ft minimum lots to General Residence (GR) with 7,500 sq ft minimums. The city also includes Mixed Residence (MR), Central Business District (CBD), General Business (G), Industrial (I), and Waterfront (W) districts.

Key Zoning Districts

Portsmouth's primary residential zoning districts include:

• SRA (Single-Family A) — Minimum 15,000 sq ft lots with 25 ft front, 10 ft side, and 20 ft rear setbacks. Maximum height of 35 ft.
• SRB (Single-Family B) — Minimum 10,000 sq ft lots with 20 ft front, 8 ft side, and 15 ft rear setbacks. Maximum height of 35 ft.
• GR (General Residence) — Minimum 7,500 sq ft lots with 15 ft front, 6 ft side, and 12 ft rear setbacks. Maximum height of 35 ft.
• MR (Mixed Residence) — Mixed residential district allowing various housing types and densities.

Commercial and other districts include:

• CBD (Central Business) — Mixed-use district in Portsmouth's historic downtown core
• G (General Business) — Broad range of retail, office, and service uses
• I (Industrial) — Manufacturing, warehousing, and related industrial uses
• W (Waterfront) — Special district for maritime and mixed waterfront 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. Portsmouth 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 the Portsmouth Planning Department for the city's specific ADU application requirements and any local dimensional standards

Building Code

Portsmouth 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 Portsmouth generally requires obtaining the appropriate permits from the city'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 Portsmouth Zoning Board of Adjustment (ZBA).

Key Considerations

Before starting any development project in Portsmouth, 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 (including historic district and coastal/flood zone requirements)
• Determine if the property is in a flood zone using FEMA's flood map service
• Confirm whether HOA covenants or deed restrictions apply
• Contact the Portsmouth Planning Department at (603) 610-7216 for pre-application guidance

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