What approvals do I need to build an accessory dwelling unit (ADU) on my property?

Each application for a potential ADU is unique. We encourage you to come in and meet informally with the Planning Staff to discuss before making a formal application.  

There are two types of ADU – Attached and Detached – that can be created on a single-family property.  

  1. Attached: An Attached ADU is conversion of interior space, an addition to the side or on a single-family residence. Interior renovations will require Administrative Approval. Additions will require Planning Board approval through a Conditional Use Permit.  

  1. Detached: A Detached ADU will require Planning Board approval through a Conditional Use Permit. 

Staff will review each application and determine what the permitting process will require. After our informal meeting and you decide to create an ADU, a land use application must be made. This can be done using the online permitting program OpenGov. Planning and Sustainability staff will then work with you on the permitting process, making requests for any additional information if required and scheduling your application for an Administrative Approval or Planning Board review. 

What approvals do I need to construct a shed or accessory structure on my property?

A building permit is needed for a shed, or accessory structure. No accessory building, structure or use shall be located in any required front yard, or closer to a street than the principal building (Zoning Ordinance - Section 10.571) and all accessory buildings and structures shall be included in the computation of building coverage (Zoning Ordinance Section 10.574). Staff will review the building permit application to see if the proposed location impacts any wetland buffers, or is in the historic district, and you will be notified of the next steps if those regulations apply. All accessory structures are required to meet the setbacks of the Zoning District where they are located.  

  1. An accessory building or structure not more than 10 feet in height and not more than 100 square feet in area shall be set back at least 5 feet from any lot line (Section 10.573.1). 

  1. An accessory building or structure more than 10 feet in height or more than 100 square feet in area shall be set back from any lot line at least the height of the building or the applicable yard requirement, whichever is less (Section 10.573.20). 

What approvals do I need to put in a swimming pool?

A building permit is needed for any pool addition. Staff will review the application to see if the proposed location impacts any wetland buffers, or is in the historic district, and you will be notified of the next steps if those regulations apply. Swimming pools are treated as accessory structures and need to meet setbacks within their Zoning District. 

Is there a setback or buffer from wetlands? How do I know if my property is near a wetland?

Yes, there are multiple buffers from wetlands, but the standard City buffer is 100 ft. This applies to all wetlands in Portsmouth that are over 10,000 s.f. as well as the jurisdictional tidal wetlands and vernal pools in Portsmouth. In addition to the 100 ft buffer, there are specific restrictions for what a property owner can do within 0-25 ft, 25-50 ft, and 50-100 ft of a wetland boundary. Please see Article 10 in the City of Portsmouth Zoning Ordinance for more information. 

In addition to local wetland buffers, be sure to check out the New Hampshire Department of Environmental Services webpage as the state has different wetland buffers for state waters such as tidal rivers, streams, and prime wetlands. 

To see if you have a wetland or wetland buffer on your property, please check out the City’s MapGeo online mapping application and be sure to turn on the ‘Wetlands’ layer under the Theme bar. If you are still unsure, please contact Kate Homet in the Planning & Sustainability Department for more information at (603) 610-7225 or by email at kehomet@cityofportsmouth.com.  

What is the Technical Advisory Committee (TAC) and do they need to review my project?

The Site Plan Review Technical Advisory Committee, also called the Technical Advisory Committee or TAC, is composed of city staff members from various Departments that provide technical review on applications before they are reviewed by the Planning Board. Site Plan, Subdivision, and Parking Conditional Use Permit applications all require review by TAC. For more information on the Technical Advisory Committee and to view the meeting calendar, please visit the Technical Advisory Committee webpage on the City of Portsmouth website --> https://www.cityofportsmouth.com/planportsmouth/site-plan-review-technical-advisory-committee

Do I need to present my project to the Conservation Committee?

If you are a property owner submitting a Wetland Conditional Use Permit, the project will go before both the Conservation Commission and the Planning Board for approval. The Conservation Commission is advisory to the Planning Board and will make a recommendation on the application to them. Applicants or their representative will need to attend these meetings to give a presentation on the project. This is necessary to give Conservation Commission and Planning Board members a clear picture of what is being proposed as well as providing the ability to answer questions. If you have hired an outside party, such as an engineer, wetland scientist, landscape architect, etc., to produce your application, you may request that they present it on your behalf if they are willing. 

How long does the land use approval process take?

The timeline will depend entirely on the project and specifics of the application. An application that requires multiple land use approvals through different Boards will take additional time versus a simpler application that may only require one land use approval and one meeting. Typically the technical review process takes 6-8 weeks including time for the applicant to make revisions before submitting for Planning Board approval. If the application requires review by the Conservation Commission, Zoning Board of Adjustment or Historic District Commission, additional time will be required to submit applications to those other land use boards and to receive those additional approvals. If staff finds the application incomplete, if a Board votes to continue an application or if consultants need more time for plan revisions, these will all increase the approval process timeline. 

I'm opening a business, what approvals or permits do I need?

At the very minimum, you will need to submit a building permit application for a Tenant Fit-Up/New Use/Change in Use. This is to make sure that the proposed use is allowed within the proposed zone, and that there is enough parking to accommodate the use. When establishing a new business, please contact a member of the Planning & Sustainability Department early in the process to review all needed approvals and considerations. Additional considerations may include allowed uses and zoning districts, required parking spaces, potential traffic impacts, and sign requirements. 

How much signage can I have?

The amount of signage you are allotted is determined by the frontage of your establishment. Each sign district permits a different amount of signage per linear foot of frontage. All signs require a sign permit and will be reviewed by staff.  A Tenant Fit-Up/New Use/Change in Use application needs to be submitted before a sign permit can be released.  

Can I operate a business out of my home?

A home occupation is permitted in most residential districts.  See Section 10.440 (19.20) of the Zoning Ordinance for the Table of Uses outlining which Zoning Districts permit home occupation 1 and home occupation 2 uses. See Article 15 – Definitions for details on specifications for each type of home occupation.