What this article does

Article 1 establishes what the Zoning Ordinance is, why it exists, and who it applies to. Think of it as the preamble — it sets the legal stage for everything that follows.

The basics

• The ordinance applies to every parcel in Portsmouth with no exceptions unless explicitly stated elsewhere.
• No structure may be built, enlarged, or moved, and no land use changed, except in compliance with the ordinance.
• When the ordinance conflicts with another rule (a deed restriction, another ordinance, state regulation), whichever is more restrictive wins. The ordinance doesn't override private agreements, but it may be stricter than them.
• Amendments must go through the Planning Board for a recommendation before the City Council votes. The public has the right to participate.

Who enforces the rules?

The Code Official (Code Enforcement office) administers the ordinance day to day — issuing building permits, investigating violations, and ordering violations to stop.

When do you need a building permit?

Before starting any construction, reconstruction, or alteration of a building, or changing how a property is used. The permit won't be issued unless your project complies with all applicable rules.

The Zoning Board of Adjustment (ZBA)

A 7-member (+ 2 alternates) appointed board with three main powers:

Conditional Use Permits (CUPs)

More complex uses require a CUP approved by the Planning Board at a public hearing. The board can attach conditions. To get a CUP, the project must show it:

• Is compatible in design and scale with surrounding uses
• Has adequate utility infrastructure and traffic/pedestrian access
• Won't create significant adverse impacts (traffic, noise, odors, lighting)
• Won't harm natural resources or reduce nearby property values

Penalties

Violating the ordinance is fineable under state law. Each day of continuing violation is a separate offense — fines compound rapidly.

Nonconforming lots

A lot is nonconforming if it's smaller than the current minimum lot size or has less street frontage than required. You generally cannot build on it without a ZBA variance — unless the lot was legally established before March 21, 1966.

Nonconforming buildings & structures

• ✅ Continue using it, maintain it, and repair it
• ✅ Restore or rebuild if damaged — rebuilding cannot make it more nonconforming; building permit must be applied for within 18 months of damage
• ✅ Install egress or accessibility components even if that slightly increases nonconformity
• ❌ Extend, enlarge, or expand in a way that increases the nonconformity without a variance

Nonconforming uses

• ✅ You can continue the use indefinitely
• ❌ You cannot expand or extend it to other parts of the building or lot
• ❌ Stop the use for more than 8 months and you permanently lose the right to it — presumed abandoned, cannot be revived
• ⚠️ You can change to a different nonconforming use if it's equally appropriate and less impactful — requires ZBA special exception

Article 5 sets the physical limits on what can be built: minimum lot sizes, required setbacks from property lines, and height limits.

Residential dimensional standards

⚖ These figures are summarized from the ordinance. Confirm current values with the Planning Department or the official ordinance before relying on them for a project.

Business & industrial dimensional standards

⚖ These figures are summarized from the ordinance. Confirm current values with the Planning Department or the official ordinance before relying on them for a project.

Key rules to know

• Setback = required yard. Measured from your property line to the nearest face of the building — not from the street edge.
• Building coverage = percentage of lot covered by all buildings (main + accessory).
• Height: to the ridge for sloped roofs; to the top of the parapet for flat roofs. Roof appurtenances (chimneys, HVAC) can typically extend 8–10 feet above the limit.
• Corner lots: Nothing over 3.5 feet within a 20-foot triangle at the corner — protects driver sightlines.
• Multifamily buildings may not exceed 160 feet in length.
• Lafayette Road: Buildings and parking on lots abutting Lafayette Road (Rte. 1 Bypass to Rye town line) must be at least 80 feet from road centerline or 30 feet from sideline — whichever is greater.

Accessory buildings

• Never allowed in the front yard or closer to the street than the main building
• Under 10 feet tall and 100 sq ft: 5-foot setback from all lot lines
• Larger: setback = building's height or district yard requirement, whichever is less
• Permit-free: One shed per dwelling unit, up to 120 sq ft, one story — no permit needed (environmental, corner vision, and Historic District rules still apply)
• Dumpsters: 20 feet from any residential lot; 10 feet from any lot line

Separation from residential districts

Portsmouth is divided into zoning districts. Your district determines what uses are permitted, what requires approval, and what is prohibited. The Zoning Map is available at the City Clerk's office, Planning Department, and through the city's GIS portal.

Residential districts

Mixed use districts

Business & industrial districts

Character & special districts

How uses are categorized

Article 5A governs the Character Districts (CD4-L1, CD4-L2, CD4-W, CD4, CD5) — downtown Portsmouth and surrounding walkable neighborhoods. This is "form-based" zoning: instead of only regulating land use, it regulates how buildings must be shaped and how they relate to the street.

What makes Character Districts different

• Rules are tied to a Regulating Plan — a detailed map showing what standards apply to specific block faces and lots
• Standards govern building placement (build-to lines rather than just setbacks), facade transparency, ground-floor active uses, and architectural character
• Article 5A takes precedence over other parts of the ordinance when there's a conflict
• Buildings typically must be built close to or at the street edge, creating the walkable streetwall that defines downtown

The Character Districts

Article 5B governs the G1 and G2 Gateway Neighborhood Mixed Use Districts along portions of Islington Street, Woodbury Avenue, and similar major corridors. Designed for walkable, transit-friendly, mixed-use development with more housing density than standard residential zones allow.

Key features

• Broad range of housing types encouraged alongside commercial uses
• Buildings must be close to the street — no parking between building and street
• Minimum 8-foot-wide pedestrian walkways required through the site

Density bonus for workforce housing

Projects including units affordable to households at or below 120% of Area Median Income (AMI) can apply for a density bonus CUP. The Planning Board may modify other standards to make affordable projects viable.

Parking in Gateway districts

• Developments within ¼ mile of a fixed transit stop on a year-round 5-days/week route may qualify for a 20% parking reduction — but this is not automatic; it requires Planning Board approval through the site review process
• No parking between building and street
• Shared parking across a multi-lot development site is allowed

Overlay districts don't replace your base zoning — they add extra rules on top. You must comply with both. When they conflict, the overlay wins.

Floodplain District (FP)

Based on FEMA flood maps updated January 29, 2021. Covers Special Flood Hazard Areas (Zones A and AE) plus extended flood hazard areas (land within 2 feet above Base Flood Elevation adjacent to a SFHA).

• All development in a flood hazard area requires a building permit
• New residential buildings: lowest floor at least 2 feet above Base Flood Elevation
• New nonresidential buildings: lowest floor at least 1 foot above BFE, or floodproofed with engineer certification
• Substantial improvements (repairs costing 40%+ of market value) trigger the same requirements as new construction

Historic District (HD)

Covers Portsmouth's downtown historic core. The Historic District Commission (HDC) reviews any exterior changes visible from a public way.

• Any exterior change visible from a public way requires HDC approval before a building permit can issue
• Demolition of historic structures is strongly restricted

Downtown Overlay District (DOD)

Notable: nightclubs and bars within the DOD may locate closer to residential areas than otherwise allowed, as long as they don't directly abut a residential district.

Other overlays

• North End & West End Incentive Overlays: Allow additional density in specific neighborhoods in exchange for affordability or design criteria (embedded in Article 5A standards)
• Airport Approach Overlay (AA): Height restrictions within Pease International Tradeport flight approach paths
• Highway Noise Overlay (HNOD): New residential construction along major highways must meet noise attenuation standards

Planned Unit Developments (PUDs) let developers design projects holistically, with flexibility on individual lot dimensions, in exchange for community benefits like protected open space or affordable housing. All PUDs require a Conditional Use Permit.

Types of PUDs

• Open Space PUD (OS-PUD): Clusters development on part of a site to preserve open space. Allowed in R and SRA/SRB districts. Minimum 1 acre. Open space must be permanently protected.
• Residential Density Incentive PUD (RDI-PUD): More units than base density in exchange for affordable units. For every unit affordable at or below 120% AMI, the developer earns 1.5 additional market-rate units. Minimum 1 acre.

Accessory Dwelling Units (ADUs)

A second, smaller dwelling unit on a property with a primary single-family home. Two types:

ADU approval requirements

Rules that apply to all ADUs

• The property owner must occupy either the primary unit or the ADU
• Neither unit may be used as a short-term rental (Airbnb, VRBO, etc.)
• One additional off-street parking space required for the ADU
• Exterior must be architecturally consistent with the main house — matching materials, roof forms, window patterns, siding
• Detached ADUs must be at least 5 feet from the main structure (or more per Building Code)
• If on private septic, the system must handle combined demand for both units

Converting single-family homes to multifamily

Coliving facilities

Shared housing with private sleeping areas and shared common space — adopted May 5, 2025. Requires a Conditional Use Permit in Business (B) and Gateway (G1, G2) districts. Requirements include 24/7 on-site management, posted contact signage, and annual city reporting.

Small structures — permit-free shed rule

One detached shed per dwelling unit, up to 120 sq ft, one story — no permit required. Environmental, corner vision, and Historic District rules still apply.

Unregistered vehicles

Vehicles with two or more axles that are unregistered, uninspected, or inoperable cannot remain outdoors on a lot for more than 60 days in any 12-month period unless enclosed in a building.

Small wind energy systems

Turbines up to 100 kW for on-site use. Setback from neighboring buildings: 1.5× total height. Setback from lot lines and utility lines: 1.1× height. Must also meet base zone principal structure setbacks.

Wireless telecommunications facilities

Portsmouth strongly prefers co-location (multiple carriers on one tower) and building-integrated antennas over new freestanding towers. Approval by special exception, expires after 5 years, requires a removal bond.

Sexually oriented businesses

Subject to location restrictions requiring separation from residential districts, schools, churches, and other adult businesses (Section 10.930).

Article 10 protects Portsmouth's natural resources — particularly wetlands, water quality, and slope stability. If your property has wetlands, is near water, or involves significant grading, these rules affect what you can build.

Wetlands protection

Development within or adjacent to wetlands requires state permits (NH Wetlands Bureau) before city permits can issue. Buffer zones around wetlands restrict or prohibit development. Buffer dimensions depend on wetland type and quality.

Grading, filling & excavation

Significant earth disturbance requires permits and must not cause erosion, sedimentation, runoff onto neighboring properties, slope destabilization, or drainage hazards.

Off-street parking minimums

⚖ Parking minimums summarized from the ordinance. The 2026 floor-area amendment changes residential calculations. Confirm current requirements with the Planning Department before designing a project.

Parking location rules

• Required parking must generally be on the same lot as the use it serves
• In Gateway districts, shared parking across a development site is allowed, and parking is prohibited between the building and the street
• In Business districts, parking must be set back from front lot lines (20 ft for B; 40 ft for GB)
• Home occupation parking: 10-foot setback from side and rear lines, screened from view

Parking design

• Standard space: 8.5 feet wide × 19–20 feet deep (depending on angle)
• Two-way drive aisles: 24 feet minimum
• ADA accessible spaces required per Building Code
• Surfaces must be durable: asphalt, concrete, compacted gravel, or approved pervious surfaces
• Spaces must be marked, except for 1- and 2-family homes
• Tandem parking allowed for residential dwelling units

Landscaping & screening

The Site Plan Review Regulations (separate document) contain detailed landscaping standards. The ordinance requires screening of parking lots from residential uses and streets, and vegetative buffers around certain industrial uses.

General principles

• Signs must be maintained in good condition — faded or damaged signs are violations
• Illuminated signs must not create glare on neighboring properties or traffic
• Electronic message and flashing signs are restricted in most districts
• Signs in the Historic District require HDC approval in addition to a sign permit

Residential zones

• Limited to: small nameplate signs, real estate for-sale signs, and home occupation identification signs
• Home occupation signs: typically one sign under 2 sq ft, non-illuminated

Business & commercial zones

• Wall signs (attached to building) are the primary type; size limited by facade area
• Freestanding signs allowed — typically no taller than 20–30 feet depending on district
• Each business typically gets one primary sign and limited secondary signs

Signs that don't need a permit

• Temporary real estate for-sale/for-lease signs (removed after sale)
• Construction signs on active project sites
• Public safety, traffic control, and government signs
• Interior window signs (mounted inside the glass)

Article 13 sets limits on the operational impacts of uses — how loud, smoky, bright, or vibrating a business can be at its property line. These protect neighboring properties from nuisance effects.

• Noise: Decibel limits at property lines. Stricter near residential zones and at night.
• Vibration: Must not be perceptible at neighboring property lines
• Smoke, dust, odors: Must not be discernible beyond the property line at nuisance levels
• Glare and heat: Must not project onto neighboring properties
• High hazard uses: At least 500 feet from any other high hazard use and from residential districts, with vegetated buffer

Article 14 authorizes Portsmouth to charge impact fees — one-time payments new development makes toward its proportionate share of the public infrastructure its occupants will need.

• Assessed by the Planning Board as a condition of approval
• Must be based on actual cost calculations — not arbitrary
• Held in a separate dedicated account for the specific facility collected for
• Must be spent within a specific timeframe or returned to the developer with interest
• Cannot pay for existing infrastructure deficiencies — only demand created by the new development

Significant projects (subdivisions, multifamily, commercial) expect fees for schools, roads, and parks. Single-family homeowners adding a small addition typically don't trigger impact fees.

Article 15 is the full ordinance glossary. The most commonly encountered terms in plain language. Official definitions control for legal purposes.

This guide is a summary. For legal certainty, or if you just want to go deeper, here are the official city sources.

The ordinance itself

Find your zoning district

The five boards