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State law compliance deadlines
Several HAP zoning items are driven by state mandates — not optional policy. These cannot be deprioritized.
ADUs by-right citywide
HB 577 (eff. July 1, 2025) + Portsmouth February 2026 ordinance update. Detached and attached ADUs are now by-right. No CUP required.
Parking cap (SB 284)
Effective Sept 13, 2025 (RSA 674:16, VII). Caps residential parking at 1 space/unit, with no exceptions — the former 1.5 allowances for 10+ unit developments and workforce studios/1-BRs were struck by SB 284. Portsmouth’s minimums (up to 2/unit) exceed the cap and must be amended. Ch. 329 adds a bar on requiring garaged spaces, eff. Sept 13, 2026.
Multifamily in commercial zones (HB 631 → Ch. 319 → Ch. 329)
Ch. 319 has been in force since July 1, 2026: Portsmouth shall allow multi-family dwelling units on commercially zoned land subject to an infrastructure test. Ch. 329 tightens this on Sept 13. The ordinance is superseded to the extent it conflicts, whether or not it is amended.
- Municipalities shall allow multi-family dwelling units on commercially zoned land where infrastructure is adequate (RSA 674:80, I)
- Planning board may require traffic study, water and sewer connection proof; may deny only on the grounds in II — including an abutting well owner showing their well cannot meet existing demand
- Applicant may supply inadequate infrastructure rather than be denied
- Ground-floor retail authority retained (IV); industrial-zone restriction retained (III)
- Adaptive reuse exemption from setback, height, frontage available now (V)
- Multifamily allowed as a matter of right; no additional requirements unless expressly authorized — “by right” is not in current law until this date
- Frontage, setback, height may not differ from what commercial development gets in the same district
- Nonconforming structures may be converted where the envelope is not further violated
- Attorney’s fees recoverable on improper denial
- No garaged parking space may be required
- The adaptive reuse exemption at left is repealed and replaced by dimensional parity
- Special assessment districts authorized (RSA 162-X)
Scope limit on both: the mandate reaches only structures containing more than 2 dwelling units (RSA 674:43, I). Duplexes are outside it, and because the test is per structure rather than per project, cottage courts and similar small-building forms may be outside it too. Portsmouth retains full authority over those types.
Single-family zones dominate Portsmouth’s residential land
The R, SRA, and SRB zones together cover 2,276 acres — 85.8% of all residential land in the city. These zones currently allow only single-family homes by-right. Virtually all missing middle housing requires a variance or is prohibited outright.
Any serious housing production strategy eventually has to engage Z-33 (single-family zone reform). The dependency note flags this requires anti-speculation groundwork first. But the scale of the problem should inform how the committee weights zoning category items overall.
Zone structure — the 10 zones that matter most for housing HAP
| Code | Name | Land share | Housing types currently permitted | Key HAP items |
|---|---|---|---|---|
| R Rural Residential |
Rural Residential | 5-acre min. lot |
SFH by-right ADU by-right Multifamily: prohibited | Z-8, Z-33 |
| SRA / SRB Single Residence A & B |
Single Residence | Together ~85% res. land |
SFH by-right ADU by-right 2-family: variance 3+: prohibited | Z-5, Z-8, Z-33 |
| GRA / GRB General Residence A & B |
General Residence | 7,500 sf min. |
SFH + 2-fam by-right ADU by-right 3–4 unit by-right 5–8: special exception | Z-5, Z-8, Z-26 |
| GRC General Residence C |
General Residence C | 3,500 sf min. |
SFH through 4-unit by-right 5–8: special exception 8+: prohibited | Z-5, Z-8 |
| G1 / G2 Gateway Mixed Use |
Gateway Mixed Use | Major corridors |
Broad housing by-right Density bonus: CUP Workforce bonus available | Z-6, Z-7, Z-12, Z-22, Z-23 |
| CD4 / CD5 Character Districts |
Character Districts (downtown) | Downtown core |
Mixed use by-right Multifamily by-right Form-based standards apply | Z-7, Z-11, Z-26, Z-35 |
| OR Office / Research |
Office Research | 3-acre min. |
Ordinance text: residential prohibited Superseded — RSA 674:80 in force since Jul 1, 2026 By right + fee-shifting Sept 13 | Z-1, Z-3, Z-25, Z-29 |
| B / GB Business zones |
Business / General Business | Highway corridors |
Ordinance text: CUP in B GB: residential limited Superseded — RSA 674:80 in force since Jul 1, 2026 CUP likely unenforceable Sept 13 | Z-3, Z-25, Z-29, Z-35 |
This matrix does not show the commercial districts (OR, B, GB), and that is now the gap that matters. Multi-family dwelling units on commercially zoned land are governed by RSA 674:80, not by the local pathway shown above: the mandate has been in force since July 1, 2026 and becomes by-right with fee-shifting on September 13, 2026. Two caveats carry into this table as well — the statute reaches only structures with more than 2 dwelling units, so the 2-family / duplex row is unaffected by state law everywhere; and because the test is per structure, the cottage / cluster and coliving rows may fall outside it regardless of unit count. Portsmouth retains full authority over all three.
⚖ Simplified for triage orientation. Confirm specific parcel rules with the Planning Department or the plain English guide.
Approval pathway by housing type — current Portsmouth rules
| Housing type | R / SRA / SRB | GRA / GRB | GRC | G1 / G2 | CD4 / CD5 |
|---|---|---|---|---|---|
| Single-family | By-right | By-right | By-right | By-right | By-right |
| ADU (attached or detached) | By-right ★ | By-right ★ | By-right ★ | By-right | By-right |
| 2-family / duplex | Variance | By-right | By-right | By-right | By-right |
| 3–4 unit multifamily | Prohibited | By-right | By-right | By-right | By-right |
| 5–8 unit multifamily | Prohibited | Sp. exception | Sp. exception | By-right | By-right |
| 9+ unit multifamily | Prohibited | Prohibited | Prohibited | By-right | By-right |
| Cottage / cluster housing | No pathway | No pathway | No pathway | CUP | CUP |
| Coliving | Prohibited | Prohibited | Prohibited | CUP (B, G1, G2) | CUP |
★ By-right as of HB 577 (July 2025) + Portsmouth February 2026 ordinance update.
All 38 Z-items grouped by mechanism — click any to expand