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Housing Action Plan — Context Module 6

The Missing Middle:
Housing Types Portsmouth Lacks

Portsmouth's current zoning creates a gap between single-family homes and large apartment buildings — a range of housing types that once defined New England neighborhoods but are now largely prohibited from being built new. Understanding this gap is essential to evaluating the zoning category of the Housing Action Plan.

"Missing middle" housing refers to multi-unit or clustered housing types compatible in scale with single-family neighborhoods — duplexes, triplexes, fourplexes, cottage courts, townhouses, and small apartment buildings. They are "missing" not because they don't exist in Portsmouth's older neighborhoods, but because current zoning largely prevents building new ones.

The housing type spectrum — click any type to explore

The legal and regulatory frame

Why missing middle is banned

Most of Portsmouth's residential zones permit single-family homes as-of-right but require a variance or special exception for duplexes, triplexes, or small multifamily. These are the same housing types that make up much of Portsmouth's older, walkable neighborhoods — built before current zoning existed.

RSA 672:1 III-e — prohibition on unreasonable discouragement of housing

The zoning history

Mid-20th century zoning reforms replaced use-mixed neighborhood patterns with single-use residential zones. The result is that buildings considered normal in Portsmouth's historic core are nonconforming — and illegal to replicate — in most of the city's residential land area.

See also: HAP items Z-22 through Z-30 (zoning reform category)

Housing Action Plan items that address the missing middle

Several HAP zoning items directly expand what types of housing are permitted and in which zones.

Z-2 + P-2
ADU ordinance enhancements + Administrative approval for ADUs
The by-right baseline is now achieved — HB 577 (July 2025) and Portsmouth's March 2026 ordinance update make ADUs by-right citywide. Z-2 now addresses enhancements beyond state compliance: dimensional standards, design guidance, and ordinance optimization. This is the HAP's most recent tangible win and a model for how zoning reform produces results.
Z-26 + Z-5
Reduce conditional use permits for housing + Missing middle housing allowances
Z-26 reduces the CUP burden that forces small multifamily through discretionary review. Z-5 directly addresses missing middle housing allowances — expanding the types and configurations permitted in residential zones to replicate Portsmouth's pre-zoning neighborhood patterns.
Z-9
Cottage housing / cluster development provisions
Creates a regulatory pathway for cottage courts and small clustered housing — a type common in Portsmouth's historic fabric but currently without a clear by-right option. Z-9 establishes the standards needed to permit this form without a variance.
Z-8
Lot size and dimensional requirement updates
Current lot size minimums and dimensional standards often make missing middle types physically impossible on existing infill lots, even when the use is technically permitted. Z-8 is a precondition for many other zoning items to have real reach.
Z-5
Missing middle housing allowances
Z-5 directly targets the missing middle gap — expanding the range of housing types permitted as-of-right in residential zones. This is the core zoning item for filling in the spectrum between single-family homes and large apartment buildings.

For triage: Missing middle items in the HAP are not about large-scale development — they're about replicating the building patterns already present in Portsmouth's most livable neighborhoods. The question for each item is whether it gives those patterns a legal pathway, and whether that pathway requires discretionary review or is truly by-right.