Manchester ADU permit requirements
Last reviewed: June 22, 2026
Quick answer
Permitting an accessory dwelling unit (ADU) in Manchester, New Hampshire means pulling a building permit from the local authority that issues it. ArchPermit tracks 12 source-cited requirements (10 required, the rest conditional) for this jurisdiction. Submittals go through gTechna online portal (building) + Planning Board (CUP). These requirements were last reviewed June 22, 2026; confirm the exact forms and fees with the local permitting authority.
A source-cited checklist of what an ADU (accessory dwelling unit) permit package needs in City of Manchester. Every item links to its authoritative source; items that vary are flagged to confirm locally.
Manchester currently requires a Conditional Use Permit (CUP) from the Planning Board BEFORE building permits; ADUs are allowed by CUP in all residential districts (R-S, R-1A, R-1B, R-2, R-3, R-SM). One ADU per single-family dwelling, only within the dwelling or its attached/detached garage; owner-occupancy required (common ownership, no condominium); ≤2 bedrooms; ≤750 sf gross floor area; +1 off-street parking per ADU bedroom. A Certificate of Occupancy AND a Certificate of Compliance are required before the ADU is recognized. ⚠️ NH RSA 674:71–73 (eff July 1 2025) requires municipalities to allow one attached + one detached ADU by-right with no permits other than building permits — Manchester's CUP requirement and garage-only/no-detached rule appear to predate / not yet reflect the state mandate; confirm with PCD whether the CUP step still applies.
- Abutter List (RSA 672:3)required
Names + mailing addresses of all abutting owners of record, for the CUP public hearing.
source · reviewed 2026-06-22 - Building Permit Application + Feerequired
Applied online via gTechna (or paper), reviewed for Building Code + Zoning Ordinance compliance.
source · reviewed 2026-06-22 - Certificate of Occupancy + Certificate of Compliancerequired
Both required before the ADU is City-recognized; cannot be granted without prior approval of all building permits + Housing Code conformance.
source · reviewed 2026-06-22 - Conditional Use Permit (CUP) Applicationrequiredverify locally
Planning Board CUP, signed by the owner, obtained before the building permit (currently required; NH RSA 674:71–73 may now bar requiring it — confirm with PCD).
source · reviewed 2026-06-22 - Copy of Deed + Tax Map + Property Cardrequired
A copy of the deed with lot description, plus the tax map and current property card.
source · reviewed 2026-06-22 - Electrical / Plumbing / Heating Permit Applicationsrequired
Separate trade permits by licensed trades; filled online but printed, signed, and mailed with fees (not accepted electronically).
source · reviewed 2026-06-22 - Floor Plans / Elevations (6 copies)required
Floor plans plus elevations (required for any new construction, including additions).
source · reviewed 2026-06-22 - Letter Addressing Article 12.05 + Architectural-Consistency Criteriarequired
Written narrative addressing the CUP decision criteria; the Board must find the exterior architecturally consistent with the primary residence.
source · reviewed 2026-06-22 - Means-of-Egress / Fire-Safety / Ventilation Compliancerequired
Two means of egress per unit; bedroom emergency egress; hardwired smoke + CO detectors; habitable-room window area ≥1/10 floor area; bathroom window ≥3 sf or mechanical ventilation.
source · reviewed 2026-06-22 - Plot / Site Plan (6 copies, to scale)required
Existing conditions + proposed changes: lot, building, parking, setbacks, driveways, streets, all setback information noted.
source · reviewed 2026-06-22 - Owner Affidavit (if owner ≠ applicant)conditional
A signed affidavit from the owner when the owner is not the applicant/agent.
source · reviewed 2026-06-22 - Wastewater / Septic Provisionconditional
If not on municipal sewer, the septic system must meet NH WSPCD requirements (RSA 485-A:38).
source · reviewed 2026-06-22