ACCESSORY DWELLING UNITS IN NEW HAMPSHIRE A Guide for

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ACCESSORY DWELLING UNITS IN NEW HAMPSHIRE

A Guide for Municipalities

ACCESSORY DWELLING UNITS IN NEW HAMPSHIRE: A GUIDE FOR MUNICIPALITIES

December 2017

Written and edited by

Benjamin D. Frost, Esq., AICP |

Director of Legal and Public Aairs | bfr[email protected]

New Hampshire Housing Finance Authority

Prepared with the assistance of ADG, LLC

NEW HAMPSHIRE HOUSING FINANCE AUTHORITY | 603-472-8623 | P.O. Box 5087 | Manchester, NH 03108 | NHHFA.org

New Hampshire Housing Finance Authority | Board of Directors

Stephen W. Ensign, New London – Chair | Amy L. Lockwood, Deerﬁeld – Vice Chair

Kendall Buck, Wilmot | John A. Cuddy, North Conway | Pauline Ikawa, Manchester

Connie Boyles Lane, Concord | Mary Beth Rudolph, Dover | Stephanye Schuyler, Portsmouth

Donald L. Shumway, Hopkinton

Dean J. Christon, Executive Director

ACCESSORY DWELLING UNITS IN NEW HAMPSHIRE: A GUIDE FOR MUNICIPALITIES | December 2017

New Hampshire Housing

TABLE OF CONTENTS

New Hampshire Accessory Dwelling Units Law | page 4

RSA 674:71 - 73

INTRODUCTION | page 6

ADUs: Expanding Housing Opportunities in New Hampshire Communities

PART 1 | page 8

Understanding New Hampshire’s Accessory Dwelling Units Law

1.0 New Hampshire Accessory Dwelling Units Law Explainer Table

1.1 What is an ADU?

1.2 How ADUs Beneﬁt Homeowners

1.3 Financial Impact of ADUs on Communities

1.4 ADU Technical and Legal Considerations

1.4.1 Model ordinances

1.4.2 Zoning ordinances and compliance with the ADU law

1.4.3 Blending ADUs into the character of a neighborhood

1.4.4 State and municipal codes and standards

1.4.5 Dierences between a house with an ADU and a two-family house

1.4.6 Who may live in an ADU

PART 2 | page 16

Implementing the ADU Law

2.0 Requirements for Municipalities

2.1 Options for Municipalities: Building Your Own Ordinance

2.2 Adding to Your Zoning Ordinance

2.3 Community Acceptance and Approval

PART 3 | page 23

ADU-Related Resources

3.0 Frequently Asked Questions about ADUs

3.1 Learn More about ADUs

3.2 Appendices - Examples of New Hampshire town and city ADU ordinances

3.2.1 Town of Hebron Ordinance

3.2.2 Town of Hollis Ordinance

3.2.3 Town of Londonderry Ordinance

3.2.4 City of Portsmouth Ordinance

3.2.5 City of Portsmouth ADU Permit Application

3.2.6 Town of Warner Ordinance

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Section 674:71 Deﬁnition

As used in this subdivision, “accessory dwelling unit’’ means a residential living unit that

is within or attached to a single -family dwelling, and that provides independent living

facilities for one or more persons, including provisions for sleeping, eating, cooking, and

sanitation on the same parcel of land as the principal dwelling unit it accompanies.

Section 674:72 Accessory Dwelling Units

I. A municipality that adopts a zoning ordinance pursuant to the authority granted

in this chapter shall allow accessory dwelling units as a matter of right or by either

conditional use permit pursuant to RSA 674:21 or by special exception, in all zoning

districts that permit single-family dwellings. One accessory dwelling unit shall be

allowed without additional requirements for lot size, frontage, space limitations, or

other controls beyond what would be required for a single -family dwelling without

an accessory dwelling unit. The municipality is not required to allow more than one

accessory dwelling unit for any single -family dwelling. The municipality may prohibit

accessory dwelling units associated with multiple single-family dwellings attached

to each other such as townhouses, and with manufactured housing as deﬁned in

RSA 674:31. Subsequent condominium conveyance of any accessory dwelling unit

separate from that of the principal dwelling unit shall be prohibited, notwithstanding

the provisions of RSA 356-B:5, unless allowed by the municipality.

II. If a zoning ordinance contains no provisions pertaining to accessory dwelling units,

then one accessory dwelling unit shall be deemed a permitted accessory use, as a

matter of right, to any single -family dwelling in the municipality, and no municipal

permits or conditions shall be required other than a building permit, if necessary.

III. An interior door shall be provided between the principal dwelling unit and the

accessory dwelling unit, but a municipality shall not require that it remain unlocked.

IV. Any municipal regulation applicable to single- family dwellings shall also apply to the

combination of a principal dwelling unit and an accessory dwelling unit including,

but not limited to lot coverage standards and standards for maximum occupancy

per bedroom consistent with policy adopted by the United States Department of

Housing and Urban Development. A municipality may require adequate parking to

accommodate an accessory dwelling unit.

TITLE LXIV - PLANNING AND ZONING

CHAPTER 674 -

LOCAL LAND USE PLANNING AND REGULATORY POWERS

Accessory Dwelling Units eective June 1, 2017

RSA 674:71 - 73

ACCESSORY DWELLING UNITS LAW

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New Hampshire Housing

V. The applicant for a permit to construct an accessory dwelling unit shall make adequate

provisions for water supply and sewage disposal for the accessory dwelling unit in

accordance with RSA 485 -A:38, but separate systems shall not be required for the

principal and accessory dwelling units. In order to comply with this paragraph and prior

to constructing an accessory dwelling unit, an application for approval for a sewage

disposal system shall be submitted in accordance with RSA 485-A

as applicable.

The approved sewage disposal system shall be installed if the existing system has

not received construction approval and approval to operate under current rules or

predecessor rules, or the system fails or otherwise needs to be repaired or replaced.

VI. A municipality may require owner occupancy of one of the dwelling units, but it shall not

specify which unit the owner must occupy. A municipality may require that the owner

demonstrate that one of the units is his or her principal place of residence, and the

municipality may establish reasonable regulations to enforce such a requirement.

VII. A municipality may establish standards for accessory dwelling units for the purpose of

maintaining the aesthetic continuity with the principal dwelling unit as a single -family

dwelling. A municipality may also establish minimum and maximum sizes for an accessory

dwelling unit, provided that size may not be restricted to less than 750 square feet.

VIII. A municipality may not require a familial relationship between the occupants of an

accessory dwelling unit and the occupants of a principal dwelling unit.

IX. A municipality may not limit an accessory dwelling unit to only one bedroom.

X. An accessory dwelling unit may be deemed a unit of workforce housing for purposes of

satisfying the municipality’s obligation under RSA 674:59 if the unit meets the criteria in

RSA 674:58, IV for rental units.

Section 674:73 Detached Accessory Dwelling Units

A municipality is not required to but may permit detached accessory dwelling units. Detached

accessory dwelling units shall comply with the requirements of, and any municipal ordinances

or regulations adopted pursuant to, RSA 674:72, IV through IX. If a municipality allows

detached accessory dwelling units, it may require an increased lot size.

Statute text includes amendments adopted by the Legislature in 2017.

RSA 674:71 - 73

ACCESSORY DWELLING UNITS LAW (cont’d)

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New Hampshire Housing

With a limited supply of affordable apartments and houses in New Hampshire to meet the needs of

a growing economy and changing demographics, accessory dwelling units (ADUs) are an important

component of expanding the availability of housing in the state.

The New Hampshire Accessory Dwelling Units statute (RSA 674:71 - 73) became law on June 1,

2017. As expressed by the Legislature, the intent of the law is to expand the supply of housing in

New Hampshire communities without further land development, as well as to encourage efﬁcient use

of existing housing stock and infrastructure, and provide an affordable housing option in communities.

Accessory dwelling units are residential living units attached to or associated with a single-family

dwelling, providing independent living facilities for one or more persons (e.g., an apartment over a

garage, in a basement, in an outbuilding).

Under the law, homeowners statewide now have the right to

create an ADU for a family member, caregiver, or as a rental unit, in accordance with local ordinances.

As demographics, commuting patterns, and economics change, so do people’s needs and desires for

housing options. Recent studies demonstrate that millennials and baby boomers alike increasingly

are looking for housing that reﬂects a more compact, urban setting. The New Hampshire Legislature

recognized this trend, as indicated in the preamble to the ADU law:

There is a growing need for more diverse affordable housing opportunities for the citizens of

New Hampshire

Demographic trends are producing more households where adult children wish to

give care and support to parents in a semi-independent living arrangement

Elderly and disabled citizens are in need of independent living space for caregivers

Also, there are societal beneﬁts associated with the creation of accessory dwelling units. ADUs can:

Increase the supply of affordable housing without the need for more infrastructure or further

land development

Beneﬁt aging homeowners, single parents, recent college graduates (who can be saddled

with heavy student loan debt), caregivers, and disabled persons

Integrate affordable housing into the community with minimal negative impact

Provide elderly citizens with the opportunity to live in a supportive family environment

INTRODUCTION

Accessory Dwelling Units: Expanding Housing

Opportunities in New Hampshire Communities

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New Hampshire Housing

ADUS AND YOUR MUNICIPALITY

The ADU law was initiated by the New Hampshire Home Builders Association. It heard from its

members that they were having difﬁculty meeting client requests to construct ADUs in many commu-

nities because of local zoning restrictions. When the bill was introduced in 2015, a large coalition that

included real estate professionals, AARP, disability rights advocates, young professionals, and housing

advocates expressed a desire for greater ﬂexibility in housing options – which ADUs offer.

All New Hampshire municipalities are now faced with a choice: either pro-actively address the law’s

requirements and utilize its ﬂexibility, or let the law override any conﬂicting local zoning provisions.

We encourage you to be proactive and do at least two things:

Utilize this guide and other information about ADUs, such as that provided by the New Hampshire

Ofﬁce of Strategic Initiatives and the New Hampshire Municipal Association.

Plan for the unique needs of your community. Know what you would like your regulations to

achieve, in light of the ADU law’s requirements and options.

Working with public ofﬁcials and partner organizations, New Hampshire Housing provided technical

assistance as the state’s new ADU law was developed, and continues to provide support to communi-

ties as they implement this law.

While municipalities are not required to report ADU and workforce housing permits to the New

Hampshire Ofﬁce of Strategic Initiatives, NHOSI annually collects building permit and land use

regulation information from the state’s cities and towns.

Municipalities are strongly urged to submit information about permits to create ADUs to the NHOSI in

order to more thoroughly document New Hampshire’s housing market and long-term affordability.

This ADU guide for municipalities, along with a new ADU guide for homeowners that will be avail-

able in fall 2018, is part of the service and outreach provided by New Hampshire Housing to support

the ongoing development of affordable housing in the state.

Dean J. Christon

Executive Director

New Hampshire Housing Finance Authority

A house in Hollis, NH, with an ADU constructed to the left of the front door.

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New Hampshire Housing

Individual and family needs, along with traditional notions of homeownership, are evolving.

The millennial generation (now in their 20s and 30s) has surpassed the baby boomers (at or nearing

retirement age) to become the largest generational group in America. This creates new housing chal-

lenges for our communities.

As the largest group of potential homeowners, millennials may face student debt burdens and more

stringent credit requirements that hinder their ability to purchase a home. At the same time, boomers

may have difﬁculty staying in their homes and communities – aging in place – due to rising owner-

ship costs, ﬁxed incomes, home maintenance, and age-related physical limitations.

While there are many different ways to tackle this problem, one of the simplest involves local land

use regulations. Many communities have revised their zoning ordinances to allow accessory dwelling

units. Sometimes called “in-law” apartments, ADUs foster neighborhood diversity, increase the supply

of workforce housing, and provide homeowners with additional income.

Certain groups in New Hampshire communities may especially beneﬁt from the ADU law, such as

empty nesters and retirees, young professionals, employers, and single parents.

EMPTY NESTERS AND RETIREES

Almost three-quarters of the homes in America are owned by people 45 years or older. In many cases,

these people are discovering that their home has outgrown their needs, and they have a lot of unused

space. Some homeowners will choose to downsize and move, while others prefer to stay connected

to the communities where they’ve lived for many years. The familiarity of the physical setting and the

social networks they’ve developed are the things that make them want to “age in place.”

ADUs can allow homeowners to convert unneeded personal space for a unit in which a caregiver can

live and help with personal care and household work. These arrangements might enable older home-

owners to stay in their homes longer and maintain an independent lifestyle for many years.

PART I

Understanding New Hampshire’s

Accessory Dwelling Units Law

Architectural drawing for an addition that will become an ADU.

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New Hampshire Housing

Or, by remodeling and creating an ADU, they can convert unused living space into a rent-producing

unit, provide independent living space for themselves, or for a relative.

YOUNG PROFESSIONALS

For recent college graduates, ﬁnding an affordable place to live once they’ve found a job can be

daunting. Many young workers move back to their parents’ homes or may settle for a less desirable

job due to location and housing affordability concerns.

An even greater challenge for young adults is the ability to become a homeowner. The median age of

ﬁrst-time homebuyers nationally is 32 years, the highest it’s ever been. Part of millennials’ delay in

purchasing a home is based on a choice to form families later in life; part of it is economic circum-

stances that make saving for a downpayment difﬁcult.

Renting an ADU could be a housing option for some young adults. While ADU rents may be similar

to those of units in apartment complexes, tenants may be able to negotiate terms, such as agreeing

to do property maintenance (like shoveling snow or mowing the lawn) in exchange for a lower rent.

ADUs are often located in safe, established neighborhoods, close to stores and amenities such as pub-

lic transportation. ADU renters can live and work in the same town, enabling them to become part

of the community and to develop their own social networks faster. ADUs can also be a satisfactory

arrangement where the homeowner and a relative wish to have both proximity and privacy.

EMPLOYERS

ADUs not only beneﬁt owners and renters but also local employers. Finding employees and housing

for them has become a serious challenge in New Hampshire’s housing market. This is especially true

in established communities that have a shortage of affordable rental units. If employees cannot ﬁnd

affordable places to live, companies may be compelled to relocate, hindering economic development

in the area.

A healthy rental market, complete with a ready supply of ADUs, can provide the opportunity for

young workers to move into a community where businesses are established or growing, and help

satisfy the need for affordable housing for employees.

SINGLE PARENTS

Out of all families with children in New Hampshire, almost 21% are headed by single women. The

average income of single mothers is about one-third of those of married couple families, and about

two-thirds of single fathers. This income gap indicates single mothers are at a signiﬁcant disadvantage

in their ability to afford homeownership or even a decent apartment.

ADUs may provide an opportunity for single mothers to ﬁnd affordable housing for their families in

good communities. Additionally, if they purchase a home with an ADU, the rental income could help

them qualify for a mortgage.

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New Hampshire Housing

1.0 | New Hampshire Accessory Dwelling Units Law Explainer Table

Section of Law Explanation

674:71 Deﬁnition

As used in this subdivision, “accessory dwelling

unit’’ means a residential living unit that is

within or attached to a single -family dwelling,

and that provides independent living facilities

for one or more persons, including provisions

for sleeping, eating, cooking, and sanitation

on the same parcel of land as the principal

dwelling unit it accompanies.

• The four deﬁning elements – provisions for

sleeping, eating, cooking, and sanitation –

must be allowed by the municipality for the

unit to constitute an ADU.

• This may all be done in a relatively small space,

such as a studio apartment or “tiny home,” or it

may be in a larger unit with multiple rooms.

674:72 Accessory Dwelling Units

I. A municipality that adopts a zoning ordinance

pursuant to the authority granted in this

chapter shall allow accessory dwelling units

as a matter of right or by either conditional

use permit pursuant to RSA 674:21 or by

special exception, in all zoning districts that

permit single-family dwellings. One accessory

dwelling unit shall be allowed without

additional requirements for lot size, frontage,

space limitations, or other controls beyond

what would be required for a single-family

dwelling without an accessory dwelling unit.

The municipality is not required to allow more

than one accessory dwelling unit for any

single-family dwelling. The municipality may

prohibit accessory dwelling units associated

with multiple single-family dwellings attached

to each other such as townhouses, and with

manufactured housing as deﬁned in RSA

674:31. Subsequent condominium conveyance

of any accessory dwelling unit separate from

that of the principal dwelling unit shall be

prohibited, notwithstanding the provisions

of RSA 356-B:5, unless allowed by the

municipality.

• The municipality needs to choose how it will

allow ADUs: by right (generally requiring only

a building permit), by special exception (board

of adjustment), or by conditional use permit

(often the planning board, but other ofﬁcials

can be involved; see RSA 674:21, II).

• The municipality must allow at least one

attached ADU wherever single-family

residences are also allowed by zoning.

• Regardless of how ADUs are allowed, the

municipality cannot impose greater dimensional

standards on homes with ADUs than it does for

homes without ADUs.

• Municipalities may restrict ADUs from being

built with manufactured housing or town-

house-style units.

• ADUs may not be sold as condominiums unless

the municipality explicitly allows it; such sales

may be allowed either through zoning or

subdivision regulations.

II. If a zoning ordinance contains no provisions

pertaining to accessory dwelling units, then

one accessory dwelling unit shall be deemed a

permitted accessory use, as a matter of right,

to any single- family dwelling in the municipality,

and no municipal permits or conditions shall

be required other than a building permit, if

necessary.

• If a municipality’s zoning ordinance is silent on

the topic of ADUs, the municipality must allow

at least one attached ADU in any single-family

home.

III. An interior door shall be provided between

the principal dwelling unit and the accessory

dwelling unit, but a municipality shall not

require that it remain unlocked.

• The requirement for an interior door only

applies to attached ADUs.

• This requirement may suggest that there must

be a common wall between the units, but

local interpretation could allow ADUs above

attached garages where there might be more

than one intervening door between the ADU

and the main house.

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New Hampshire Housing

1.0 | New Hampshire Accessory Dwelling Units Law Explainer Table

Section of Law Explanation

IV. Any municipal regulation applicable to

single -family dwellings shall also apply to

the combination of a principal dwelling unit

and an accessory dwelling unit including,

but not limited to lot coverage standards

and standards for maximum occupancy per

bedroom consistent with policy adopted by

the United States Department of Housing

and Urban Development. A municipality may

require adequate parking to accommodate an

accessory dwelling unit.

• There can be no additional dimensional require-

ments for an ADU.

• Reference to HUD occupancy standards means

that a municipality can limit per-bedroom

occupancy in ADUs only if it is also doing so in

single-family homes. Check with legal counsel

about limitations before trying this.

• A municipality can require o-street parking or

some other demonstration of parking adequacy

for an ADU.

V. The applicant for a permit to construct an

accessory dwelling unit shall make adequate

provisions for water supply and sewage dispos-

al for the accessory dwelling unit in accordance

with RSA 485-A:38, but separate systems shall

not be required for the principal and accessory

dwelling units. In order to comply with this

paragraph and prior to constructing an accessory

dwelling unit, an application for approval for

a sewage disposal system shall be submitted

in accordance with RSA 485-A as applicable.

The approved sewage disposal system shall be

installed if the existing system has not received

construction approval and approval to operate

under current rules or predecessor rules, or the

system fails or otherwise needs to be repaired

or replaced.

• The property owner must demonstrate the

adequacy of water supply and sanitary disposal.

• The municipality cannot require water or

sanitary disposal systems for the ADU that are

separate from those of the principal dwelling.

• The owner may be required to have a new

septic system designed and approved if the ex-

isting system does not meet NH Department of

Environmental Services standards for the house

including the addition of the ADU. This may be

true even if the overall number of bedrooms

using the system is unchanged by the ADU’s

construction.

• A new septic system does not need to be built

unless the existing system is unlicensed or has

failed.

VI. A municipality may require owner occupancy of

one of the dwelling units, but it shall not specify

which unit the owner must occupy. A munici-

pality may require that the owner demonstrate

that one of the units is his or her principal place

of residence, and the municipality may estab-

lish reasonable regulations to enforce such a

requirement.

• The municipality may require owner occupancy

of one of the units; if it does this, the municipal-

ity should consider what it means by “owner”:

does the owner need to be a physical person, or

can it be (1) a member of an LLC that owns the

property; (2) a beneﬁciary of a revocable trust

that owns the property; or (3) a person with an

interest in another legal entity (e.g., partnership

or corporation) that owns the property.

• Residency of the owner may also be required,

and could be demonstrated through voter

registration, automobile registration, or similar

indicators of domicile.

VII. A municipality may establish standards for

accessory dwelling units for the purpose of

maintaining the aesthetic continuity with the

principal dwelling unit as a single- family dwell-

ing. A municipality may also establish minimum

and maximum sizes for an accessory dwelling

unit, provided that size may not be restricted to

less than 750 square feet.

• Standards to perpetuate the “look and feel” of

a single-family home may be required by the

municipality, and this may best be done through

a permit by special exception or conditional use

permit.

• ADU minimum and maximum size may be spec-

iﬁed, but the municipality cannot require ADUs

to be smaller than 750 s.f. The owner, however,

may build a unit smaller than that, subject to

local ADU unit size minimum, if any.

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New Hampshire Housing

1.0 | New Hampshire Accessory Dwelling Units Law Explainer Table

Section of Law Explanation

VIII. A municipality may not require a familial

relationship between the occupants of an

accessory dwelling unit and the occupants of

a principal dwelling unit.

• Despite the colloquial name “in-law apartment,”

a municipality may not limit ADU occupancy

to family members of the owners of the main

dwelling.

IX. A municipality may not limit an accessory

dwelling unit to only one bedroom.

• A municipality may limit an ADU to two bed-

rooms, but not to one.

X. An accessory dwelling unit may be deemed

a unit of workforce housing for purposes of

satisfying the municipality’s obligation under

RSA 674:59 if the unit meets the criteria in

RSA 674:58, IV for rental units.

• This section only means that if an ADU meets

the rental price standards of the Workforce

Housing Law, then the municipality may count

the unit as part of its “fair share” calculation.

• The reference to workforce housing does not

confer upon a municipality the authority to

impose aordability restrictions on the ADU.

674:73 Detached Accessory Dwelling Units

A municipality is not required to but may permit

detached accessory dwelling units. Detached

accessory dwelling units shall comply with the

requirements of, and any municipal ordinances

or regulations adopted pursuant to, RSA 674:72,

IV through IX. If a municipality allows detached

accessory dwelling units, it may require an

increased lot size.

• A municipality may choose to allow detached

ADUs wherever attached ADUs are allowed, in a

more limited geographical area, or not at all.

• Only regarding detached ADUs may a munici-

pality require an increased lot size, but it is not

necessary to do so.

• Perhaps more important for a municipality to

consider is a proximity requirement, so that the

detached ADU is somehow physically associ-

ated with the main home, instead of being in a

remote location on the lot.

Statute text includes amendments adopted by

the Legislature in 2017.

Explanation column written by

Benjamin D. Frost, Esq., AICP

New Hampshire Housing Finance Authority

An ADU is seen attached to the left side of this home in Hollis, NH.

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1.1 | What is an ADU?

An ADU is an additional dwelling unit that is secondary to the primary unit. It is not an equal or

duplicate unit, which would result in the creation of a duplex. An ADU may be an interior part of an

existing building, an attached extension of an existing building, a conversion of an out-building (such

as a garage, barn, or shed), built as part of a new single-family home, or as a new detached building.

RSA 674:71 deﬁnes an ADU as: a residential living unit that is within or attached to a single-family

dwelling, and that provides independent living facilities for one or more persons, including provisions

for sleeping, eating, cooking, and sanitation on the same parcel of land as the principal dwelling unit

it accompanies. Refer to pages 4 - 5 for the full RSA 674:71 - 73 text.

The state statute only requires municipalities to allow attached ADUs; it is up to local ofﬁcials as to

whether to allow detached ADUs.

1.2 | How ADUs Beneﬁt Homeowners

First-time – and post-retirement – homeownership can be challenging. An ADU can help offset the

ﬁnancial pressures associated with homeownership for a young family just starting out, and for

homeowners in their retirement years.

For example, consider a young couple who has saved for a downpayment

on their ﬁrst home, but the mortgage will strain their ﬁnances. In phase 1,

they purchase the home and ﬁnance the creation of an ADU. By renting it

to a local teacher, the income makes their mortgage payments affordable.

Several years later, this family has grown and needs the additional space

of the ADU. Their salaries have increased and the mortgage is manageable

without the ADU rental income. They enter phase 2 and convert the ADU

into family living space.

Fast-forward 20 years. The kids have grown and the homeowners have

retired, and they no longer need a spacious house. Entering phase 3, they

convert the addition back into an ADU and move into it. By renting the

main house out, they supplement their retirement income.

1.3 | Financial Impact of ADUs on Communities

ADUs can aid economic development by helping to attract and retain a workforce.

ADUs can help reduce demand on healthcare facilities by providing living space for caregivers to look

after elderly homeowners who otherwise would have to leave their homes.

ADUs can increase property values, and thus add to the tax base.

By allowing ADUs by Conditional Use Permit or by Special Exception, a municipality will need

to plan for staff time to review and act on applications.

If a municipality requires owner-occupancy, it will need to provide a deﬁnition, methods and

standards in order to certify and enforce this requirement.

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1.4 | ADU Technical and Legal Considerations

1.4.1 | Model Ordinances

Both the New Hampshire Municipal Association and the Rockingham Planning Commission have

created simple model zoning provisions for ADUs, but neither includes full consideration of the

options available for municipal adoption, such as “aesthetic continuity” (design standards that

will maintain the look and feel of a single-family home).

Refer to Part 3.2 - Examples of ordinances from New Hampshire municipalities.

1.4.2 | Zoning ordinances and compliance with the ADU law

Your planning board should conduct a review of your ordinance and determine how it does – and

does not – comply with the standards of the law. Based on that assessment, it should propose

amendments to the ordinance. If your zoning ordinance does not comply with the ADU statute,

the ADU law supersedes it. If your zoning ordinance is silent on the subject of ADUs, an attached

ADU must be allowed in any single-family home.

The municipality can enact different ADU standards in different zoning districts and

neighborhoods as it deems appropriate. For example, ADUs might be allowed by right in rural

areas where neighborhood impact is unlikely, but by special exception in more densely built areas

and in historic districts, where the neighborhood impact of an ADU might be of greater concern.

Refer to Part 2.2 - Crafting ADU Provisions for Your Zoning Ordinance.

If you address ADUs in your zoning ordinance, you have a variety of choices. First, communities

may allow ADUs through different zoning mechanisms. They may be allowed:

“By right” as a permitted use without additional requirements,

By conditional use permit (usually the planning board), or

By special exception (zoning board of adjustment).

In addition, the ADU law gives municipalities discretion to decide:

Whether to limit the number of ADUs per lot

What parking standards should apply to ADUs, if any

Whether to allow detached ADUs, and if allowed, whether to require additional lot size for them

Whether to require owner occupancy of properties containing ADUs, and to determine methods

and standards for veriﬁcation and enforcement

The minimum and maximum ADU sizes, except there cannot be a requirement that an ADU be

less than 750 square feet

Whether to impose design standards on ADUs to maintain the appearance of a single-family

house

Whether to limit the number of bedrooms in an ADU to no more than two

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1.4.3 | Blending ADUs into the character of a neighborhood

You may set neighborhood compatibility standards for ADUs, and set them differently for

different zoning districts. Examples include:

Being subsidiary to the principal dwelling unit in size and function

Being consistent with the principal dwelling in appearance, design, colors, and materials

Not having its entry face the street as a second front door

Requiring a single driveway for use by both units

Requiring that any second-ﬂoor egress from an ADU should not be visible from the public way

1.4.4 | State and municipal codes and standards

As with any other new construction or residential occupancy, ADUs must comply with health,

building, mechanical, safety, environmental, accessibility, emergency response, and similar codes

and requirements for single-family residential housing.

1.4.5 | Dierences between a house with an ADU and a two-family house

Some zoning districts allow two-family homes. This is not the same as a single-family home

with an ADU. A two-family home might not have a connecting interior door between the units,

whereas an ADU must have one. Also, a two-family home commonly will have units of roughly

equal size, whereas an ADU must be smaller than (accessory, meaning secondary or subservient

to) the principal dwelling.

1.4.6 | Who may live in an ADU

How many people may live in an ADU?

The ADU law does not specify limits on the number of occupants in an ADU and does not

prevent municipalities from doing so. However, the municipal occupancy standards must comply

with federal law. Refer to Part 3.1 - HUD Bedroom Occupancy Standards.

Occupancy guidelines established by the U.S. Department of Housing and Urban Development

suggest that while a municipality may generally limit occupancy to two people per bedroom,

whether such a limitation is appropriate will depend on the circumstances (such as family

composition or the size of a room).

Must the owner reside on the property?

Not necessarily, but the municipality may require owner occupancy of one of the units. It may

require that the owner occupy a unit as his/her principal dwelling – generally meaning that the

owner will live in the unit for a majority of the year.

Must the homeowner reside in the principal dwelling unit?

No. Although the ADU law allows municipalities to require owner occupancy, the municipality

cannot specify in which unit the owner must live.

Must the occupants of the principal unit and the ADU be related to one another?

No. The ADU law prohibits municipalities from requiring a familial relationship between the

occupants of the units.

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The ADU law (refer to pages 4 - 5 for the full text of RSA 674:71 - 73) requires that every munici-

pality that adopts a zoning ordinance pursuant to the authority granted in RSA Chapter 674 shall also

allow accessory dwelling units (ADUs) as a matter of right or by either conditional use permit pursu-

ant to RSA 674:21 or by special exception, in all zoning districts that permit single-family dwellings.

The ADU legislation adds three new sections to state statute:

674:71 Deﬁnition of Accessory Dwelling Units

674:72 Accessory Dwelling Units

674:73 Detached Accessory Dwelling Units

It is important to recognize that the word “accessory” has a speciﬁc legal meaning in the context of

zoning ordinances. Through a variety of cases, the New Hampshire Supreme Court has stated that

accessory uses are those that are customarily associated with and are secondary to the primary use of

the property, such as a garage on the same lot as a house.

Here, the legislature has eliminated the need to inquire whether ADUs are customarily associated with

a single-family home, but has left it generally open for municipalities to decide how to determine

whether an ADU is secondary to the single-family home. In most cases, this would be done by

comparing the relative sizes of the housing units. For example, if a house has 2,000 sq. ft. of living

space, an associated ADU of 1,000 sq. ft. probably could be considered “accessory.”

ADUs Exist in a Wide Variety of Forms and Types:

Within the existing footprint of a house

As an addition to a house

In a detached structure, such as a garage, barn, or carriage house

As a group of small structures containing ADUs

2.0 | Requirements for Municipalities

The basic requirement of the ADU law is simple: through its zoning ordinance, your municipality

must allow at least one ADU for any single-family home in a district in which single-family homes are

a permitted use.

If your zoning ordinance doesn’t address ADUs, the law still applies – and your community must

allow an ADU in any single-family home, regardless of zoning restrictions.

If your zoning ordinance has provisions that are not compatible with the ADU law, then they will be

unenforceable.

PART 2

Implementing the ADU Law

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These are some examples of zoning provisions that are nonconforming and unenforceable:

Not permitting ADUs in all zoning districts in which single-family dwellings are allowed

Allowing an attached ADU only with additional requirements or standards for lot size, frontage,

height and setback or other dimensional controls, space limitations, lot coverage, maximum

occupancy per bedroom, or other controls beyond what would be required for a single-family

dwelling without an ADU

Counting an ADU as a separate dwelling for purposes of computing land use density

Prohibiting an interior door between the principal dwelling unit and the ADU

Requiring that an interior door remains unlocked

Requiring separate water and septic systems for the principal and accessory dwelling units

Specifying which unit the owner must occupy, if owner occupancy is required

Requiring a familial relationship between the occupants of an ADU and the occupants of a

principal dwelling unit

Requiring an ADU to be smaller than 750 sq. ft.

Limiting an ADU to only one bedroom

Requiring an ADU to meet workforce housing standards, such as rent restrictions, long-term

affordability requirements, and income targeting of tenants

This property in Hollis has an ADU separate from the main house.

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2.1 | Options for Municipalities: Building Your Own Ordinance

The ADU law gives municipalities considerable discretion to adopt zoning standards. The sample

language in this section can be adapted to ﬁt your own ordinance.

Deﬁning an ADU. In addition to providing a deﬁnition of ADUs, the law also requires an interior

door connecting the two dwelling units. How the ADU is deemed to be “attached” to the principal

dwelling unit is a matter of local discretion. Some communities might require a common wall

between the units, while others might require connection through heated space.

Example:

“An Accessory Dwelling Unit shall contain fully self-sufﬁcient living quarters, consisting of adequate

sleeping, bathing, cooking, and eating accommodations, and shall be connected to the principal dwelling

through an interior door.”

Standards may vary by zoning districts. While an attached ADU must be allowed in any zoning

district that permits single-family homes, there is ﬂexibility in how this might be achieved. For

example, your community could allow attached and detached ADUs by right in outlying, rural

districts, but only allow attached ADUs by right in village districts; in “thickly settled” areas you could

require a special exception with architectural standards as a condition of approval.

Some other factors that could be varied by zoning district include:

Form of approval: by right, conditional use permit, or special exception

How many ADUs per house lot

If an ADU is required to be owner-occupied

Septic System Requirements. Property owners who want to create an ADU must demonstrate the

adequacy of their septic system. Even if the number of bedrooms remains the same (for example,

changing a four-bedroom home to a three-bedroom home with a one-bedroom ADU), standards

of the N.H. Department of Environmental Services (NHDES) assume that there will be increased

discharge into the septic system from the creation of the ADU. A 2017 amendment to the ADU law

states that a new septic design may be required in such situations, but construction of a new system

cannot be required unless the existing system has failed or was never approved by DES.

Example:

“Adequate water supply and sewage disposal for an Accessory Dwelling Unit shall be provided in accor-

dance with RSA 485-A:38. If the existing septic system does not have a NHDES permit or is in a state of

failure, replacement will be required; otherwise, a new approved design may be required if the establish-

ment of the Accessory Dwelling Unit would increase system load beyond its design capacity.”

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2.2 | Adding to Your Zoning Ordinance

ADU Appearance Standards - Architecture. The ADU law says that municipalities can adopt

standards that required “aesthetic continuity” between the primary dwelling unit and the ADU. This

can apply both to attached and detached ADUs. Size, scale, and external appearance are signiﬁcant

factors that affect how an ADU will ﬁt into a neighborhood.

Your ordinance can require ADUs to be consistent with the principal building in appearance, design,

colors, materials, fenestration, door location or number of apparent front doors, massing, height, dec-

oration, and other visible single-family house characteristics.

Examples:

“The ADU shall be secondary in size and function to the principal dwelling and be consistent with the

principal dwelling in appearance, design, colors, and materials.”

“Exterior entry to the accessory dwelling shall not face the street as a second door or shall be set back

from the front of the building.”

Parking and Driveways. Your ordinance may require adequate parking for an accessory dwelling

unit. The number and location of parking spaces, driveways, and curb cuts on residential lots can

generate neighborhood concern, and your ordinance should respect these concerns.

Example:

“There shall be one parking space in the rear or side yard for the accessory dwelling and no additional

curb cut.”

Owner Occupancy. Although the ADU law prohibits municipalities from requiring the owner to

occupy a speciﬁc unit, owner occupancy of one of the units can be required. Owner occupancy can

help ensure property maintenance and orderly conduct of tenants.

In addition to requiring owner occupancy, a municipality can also require the owner to demonstrate

that the unit is the owner’s principal place of residence, or domicile. This can be shown by the owner

by automobile registration, voter registration, or other similar legal and permitting processes.

You may wish to make provisions that allow short-term lapses in owner-occupancy, for instances of

family difﬁculties, sabbatical leaves, temporary out-of-town employment, and extended absences.

You may require as a condition of obtaining a zoning or building permit that the owner sign a state-

ment declaring understanding and acceptance of the owner-occupancy requirement. Also, you could

require a periodic veriﬁcation by the owner of continuing owner occupancy.

Examples:

“The owner of a property containing an Accessory Dwelling Unit shall reside in either the principal or the

accessory dwelling, as of the date of the permit approval.”

“As part of an application for an owner to obtain a [building or occupancy] permit to build an Accessory

Dwelling Unit, the owner shall certify that the property is to remain owner occupied at all times, and

agrees to provide written certiﬁcation of continuing owner occupancy prior to the end of each

calendar year.”

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Condominium conversions. The Legislature amended the law in 2017 to expressly prohibit

condominium conversion of ADUs, unless the municipality chooses to allow it. This would need to

be permitted through the zoning ordinance or subdivision regulations.

Townhouses and manufactured housing. The ADU law was amended in 2017 to allow

municipalities to prohibit ADUs with townhouses and manufactured housing.

Workforce housing. The ADU law’s reference to the Workforce Housing Law is relevant only when a

municipality is evaluating its existing housing stock to determine whether it has met its obligation to

provide its fair share of the region’s need for housing that is affordable to low- and moderate-income

families.

A municipality may deem an ADU as workforce housing for purposes of satisfying the municipality’s

obligation under RSA 674:59 if the unit meets the standards in RSA 674:58, IV for rental units. This

does not mean that municipalities can impose rent restrictions or income limits on ADUs or their

occupants – this is not a power granted by the ADU law. Other laws may enable such controls, such

as an inclusionary zoning ordinance adopted pursuant to RSA 674:21.

Minimum and maximum ADU sizes. A municipality could specify that ADU sizes be some

proportion of the size of the principal unit as long as it does not result in a restriction to less than

750 sq. ft.

Minimum and maximum sizes for an accessory dwelling unit may be established, provided that ADUs

shall not be required to be smaller than 750 sq. ft. (they may be allowed to be smaller than that, at

the owner’s discretion).

Example:

“An ADU shall have an area of no less than 200 sq. ft. and no more than 1,000 sq. ft.”

Number of bedrooms. Your ordinance must allow ADUs to have more than one bedroom, but

owners may want to provide some “studio” or one-bedroom ADUs.

Building code occupancy standards specify minimum square footage for bedrooms, so building size

and ADU size in practice can govern or limit the number of bedrooms in an ADU.

Detached ADUs. It is up to the municipality to decide whether to allow detached ADUs. Detached

ADUs must comply with the requirements of any municipal ordinances or regulations adopted

pursuant to RSA 674:72, IV - IX.

If a municipality allows detached ADUs, it may require an increased lot size. You may wish to allow

detached ADUs in some or all of your zoning districts based on the character of various districts.

For instance, in rural districts that have existing accessory buildings (barns, milk houses, etc.), or in

older in-town neighborhoods with existing accessory buildings (carriage houses or detached garages),

ADUs can restore or enhance their economic viability.

Depending on the size of the lot, you can allow more than one detached ADU and specify where it

may be located.

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2.3 | Community Acceptance and Approval

One way or another, the ADU law requires towns and cities to permit ADUs more extensively than

most municipalities previously allowed. When it enacted the ADU law, the legislature cited a variety

of social, demographic, economic, and environmental beneﬁts to communities provided by ADUs.

For the beneﬁts to be fully realized, an open public process that engages citizens; respects their inter-

ests, fears, and concerns; and achieves consensus is recommended.

The planning board should undertake a public process to achieve an operable public consensus on

how to accommodate ADUs in ways that are appropriate and compatible with the community. An

open, inclusive, and well-publicized public process would cover these areas:

What are ADUs?

What beneﬁts do ADUs provide to the community?

What types of ADUs are possible?

What does the law require?

What are the differences between any current Accessory Dwelling or Accessory

Apartment regulations that your ordinance contains?

What are some problems that might be associated with ADUs and how can they be

avoided or mitigated?

Which of the choices enabled by the law would be appropriate to the entire

community and to its various neighborhoods and districts?

This house on a corner lot in Concord has an attached ADU.

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A community information and decision process should use public meetings, possibly augmented

through your municipal website, publicity through newspapers and other media, and discussions

with various civic organizations. It will certainly be a major topic of informal discussion with your

community. A deliberation and action scenario could comprise:

At least one initial public forum to begin the above discussion, and

A follow-up public session to review, and if need be revise, the conclusions from the initial

session or sessions.

The planning board may draft a set of recommendations about which options should be

pursued by the municipality.

Final steps to adopting an ADU ordinance include:

Planning board public discussion and action on recommendations

Planning board drafts a zoning amendment

Planning board holds a public hearing on the ﬁnal amendment and the recommendation of it

to Town Meeting, Town Council, City Council, or other governing body

Town Meeting or Council action on adoption of zoning amendment

An ADU was added to the back of this home in Warner, NH.

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3.0 | Frequently Asked Questions about ADUs

1. Isn’t a house with an ADU just a duplex?

No, a duplex is two units of comparable size in a single structure – think of a structure that has

mirror-image housing units. The word “accessory” in ADU has real meaning – the unit is intended to

be secondary to the main use of the building as a single family home, in the same way that a garage

would be of secondary importance.

2. What’s the meaning of the workforce housing provision in the ADU Law?

There’s a section in the ADU law that says that ADUs may be considered units of workforce housing

if they meet the requirements of the Workforce Housing Law. This may sound like circular logic – it

is. The only implication of this part of the ADU law is that a municipality can include an ADU with a

rental price that meets the standards of the Workforce Housing Law, if the municipality is attempting

to determine whether its existing housing stock provides its fair share of the region’s need for such

housing. This provision of the ADU law does not enable municipalities to impose rent limits on ADUs

or to require occupancy of such units by people of low or moderate incomes.

3. Do impact fees apply to a new ADU?

It depends on how the impact fee ordinance is written. As an innovative land use control (see RSA

674:21), if adopted impact fee ordinances are a part of a municipality’s overall zoning ordinance. The

ADU law says that municipalities can’t impose greater zoning requirements on a home simply because

it has an ADU associated with it. So if the impact fee ordinance imposes a fee based on the number

of residential units, then the ordinance would not apply to an ADU. But if the impact fee ordinance

is based on the number of bedrooms in a structure or some other measure associated with the size of

the structure, and creating an ADU increases that impact, then it is possible that the impact fee ordi-

nance would apply.

4. Why is there a requirement for an interior door between units?

The requirement for an interior door ensures that, in the future, the ADU can easily be re-integrated

into the principal dwelling. You should assume that the intention is to have an interior door that is

functional – that is, not one that has had its handle removed and been sheet-rocked into a wall.

5. What does “attached” mean in reference to ADUs?

While the ADU law requires municipalities to allow attached ADUs in any zoning district that allows

single-family homes, the law doesn’t deﬁne “attached.” It’s up to the individual municipality to de-

termine what it thinks it means. The requirement for an interior door between the primary dwelling

unit and the ADU suggests that there must be a common wall between them. Could a long, enclosed

breezeway meet that standard? Possibly. It might be appropriate to include a limitation on the length

of the breezeway to avoid abuse (e.g., a 300-foot-long breezeway leading to a lakeside structure that

suddenly becomes an ADU). Should any structural space between the units be heated space?

PART 3

ADU-Related Resources

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New Hampshire Housing

Possibly, but that could serve to eliminate some appropriate uses, such as converting space over an

attached garage into an ADU – the intervening garage would likely be unheated space.

6. What is the impact of the NHDES septic standards?

As of October 1, 2016, the N.H. Department of Environmental Services (NHDES) promulgated new

administrative rules for Individual Sewage Disposal Systems (Env-Wq 1000). These rules call for

increased minimum system design standards where ADUs are being created. This means, for exam-

ple, that for a 4-bedroom house to be converted into a 3-bedroom house with a 1-bedroom ADU, the

minimum design standard will be greater – even though the number of bedrooms has not increased.

But the legislature’s enactment in 2017 of HB 258 prohibits any requirement for construction of a new

system in such circumstances – unless the existing system is unlicensed or has already failed. A prop-

erty owner wishing to create an ADU must demonstrate the adequacy of the current system design to

handle the increased ﬂow of septage (based on the NHDES standards), or must submit a new design

for approval by NHDES.

7. Can homeowners’ associations or condominium documents prohibit ADUs?

Yes. These are private contractual arrangements between and among homeowners. While the munic-

ipality cannot prohibit ADUs, a developer can create a new housing development that has covenants

banning ADUs. Such restrictions are only privately enforceable, and not by the municipality.

8. ADU owner occupancy: What if the owner is a trust, LLC, or corporation?

If a municipality requires that either the principal dwelling unit or ADU must be occupied by the

owner, a strict reading of the law suggests that the owner must be a natural person. Trusts, LLCs, and

corporations are purely legal entities and have no physical presence on Earth. Therefore, they cannot

occupy space. A more relaxed reading of the law suggests that whoever controls such an entity could

be deemed the owner. This is a matter for local interpretation – at least until a court decides on it!

9. What are the HUD occupancy standards?

RSA 674:72, IV requires any local standards that limit the number of occupants per bedroom to be

“consistent with policy adopted by the United States Department of Housing and Urban Develop-

ment.” This refers to a Fair Housing Enforcement Statement of Policy from HUD published in the

Federal Register on December 22, 1998 (FR Vol. 63, No. 245, page 70982). That statement outlines

the factors that HUD will consider when evaluating the legality of occupancy policies. Many people

consider a maximum of two people per bedroom to be the rule of thumb. However, HUD indicates

that there are different factors to consider, such as: the size and conﬁguration of the housing unit; the

size and conﬁguration of the bedroom; the age of the occupants (i.e., it’s not unusual for new parents

to keep an infant in their bedroom). Before considering any such limitations on occupancy, consult

with your legal counsel. Refer to Section 3.1

10. What about the use of ADUs as short-term rentals?

The ADU law does not refer to or limit in any way their use as short-term rentals (consider the

widespread use of Airbnb, VRBO, and similar services). Some New Hampshire municipalities (e.g.,

Portsmouth) are moving ahead with regulations limiting short-term rentals, but this doesn’t mean that

an owner can’t create an ADU. They are separate issues. There are various initiatives in the legislature

to study or regulate short-term rentals, but the state of these efforts are in ﬂux.

11. What if we do nothing?

If your municipality chooses to do nothing in the face of the ADU law and your zoning ordinance is

silent on the subject, then ADUs will be allowed by right in any single-family home in your commu-

nity. The better approach is to develop reasonable regulations that are enabled by this law.

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3.1 | Learn More About ADUs

NEW HAMPSHIRE HOUSING FINANCE AUTHORITY

The NHHFA website has links to the resources and information listed below, and a PDF of this guide.

NHHFA.org/accessory-dwelling-units

NEW HAMPSHIRE MUNICIPAL ASSOCIATION ADU GUIDANCE

NHMA produced a useful and brief document, The New Law on Accessory Dwelling Units (September

2016) to guide municipal implementation of the law’s requirements. (Note that it does not incorporate

the statute’s 2017 amendments.)

www.nhmunicipal.org/Resources/ViewDocument/74

Also included here is the supporting material for the 2016 NHMA Municipal Law Lecture Series

presentation on the ADU law by Benjamin Frost of NHHFA.

NHHFA.org/accessory-dwelling-units/NHMA ADU Law Lecture 2016.pdf

NEW HAMPSHIRE OFFICE OF STRATEGIC INITIATIVES

ADU TECHNICAL BULLETIN

The NHOSI (formerly the Ofﬁce of Energy and Planning) technical bulletin on ADUs provides a

helpful explanation of the law and various issues that muncipalities should consider when developing

their regulatory response to the ADU law. (The version included here does not incorporate the

statute’s 2017 amendments.) Additionally, OSI annually collects building permit and land use

regulation information from the state’s cities and towns. Municipalities are strongly urged to include data

on ADU permits to the NHOSI.

www.nh.gov/osi/planning/resources/accessory-dwellings.htm

HUD BEDROOM OCCUPANCY STANDARDS

The ADU law requires that municipalities can only impose bedroom occupancy standards on ADUs

if they are also doing the same for single-family homes, and in either circumstance they must comply

with U.S. Department of Housing and Urban Development (HUD) policy. This policy is not perfectly

clear-cut, but rather provides guidance for any municipality or landlord that is seeking to limit the

number of people occupying a dwelling unit.

While the HUD policy states that a limit of two people per bedroom as a general rule is reasonable,

there are other factors that must also be considered such as household composition, size of rooms,

and other special circumstances.

Federal Register / Vol. 63, No. 245 / Tuesday, December 22, 1998 / Notices

DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT [Docket No. FR–4405–N–01]

Fair Housing Enforcement—Occupancy Standards; Notice of Statement of Policy (Keating Memo, 3/20/91)

www.hud.gov/sites/documents/DOC_7780.PDF

WEBSITE SPECIALIZING IN ALL THINGS ADU

This website was created by three ADU advocates from Portland, Oregon. It contains many useful

examples of ADUs, including costs of construction and permitting issues in different jurisdictions.

www.AccessoryDwellings.org

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3.2 | Appendices 3.2.1 - 3.2.6

EXAMPLES OF NEW HAMPSHIRE TOWN & CITY ADU ORDINANCES

TOWN OF HEBRON (2016 population: 621). Hebron’s zoning ordinance allows ADUs by

special exception and exercises much of the discretion allowed by the state law, including a

requirement for off-street parking, owner occupancy of one of the units, architectural consistency,

and limitation to no more than two bedrooms. The septic design provision in the ordinance is

consistent with the amendment to the 2017 amendment to the state statute on ADUs, as it does

not require installation of a new system unless DES requires it. The statement that all ADUs

will be deemed units of workforce housing is not consistent with the law, as the ordinance does

not consider the actual rental prices of the ADUs. The occupancy limitation to no more than

four persons does not clearly comply with HUD occupancy standards, as the state ADU law

requires. Appendix 3.2.1

TOWN OF HOLLIS (2016 population: 7,775) The ADU provisions in the Hollis zoning ordinance

served as a model for some of the state law’s provisions. Hollis allows ADUs by special exception,

and its provisions exercise much of the discretionary authority of the law, including a requirement

for off-street parking, maintenance of the structure’s appearance as a single-family home, and

allowing only one ADU per property. Hollis provides an operational deﬁnition of “attached”

by stating that the principal unit and the ADU “must share internal heated living space access

through a common wall.” Hollis also allows detached ADUs with an increase in lot size. The

town’s requirement that a new or upgraded septic system shall be required if the existing system is

inadequate probably is inconsistent with the 2017 amendment to the ADU law that requires only

that a new septic design must be approved by DES in such circumstances, unless the system is

unlicensed or has already failed. Appendix 3.2.2

TOWN OF LONDONDERRY (2016 population: 25,361) Londonderry’s ordinance allows both

attached and detached ADUs by right, but also calls for architectural consistency with the principal

dwelling unit. This is probably enforced at the staff level during the building permit process. The

ordinance also exercises much of the discretionary authority of the ADU Law, such as requiring

owner occupancy, off-street parking, no additional curb cuts, limitation of ADUs to two bedrooms.

The statement that all ADUs will be deemed units of workforce housing is not consistent with the

law, as the ordinance does not consider the actual rental prices of the ADUs. Appendix 3.2.3

CITY OF PORTSMOUTH (2016 population: 21,524). Portsmouth adopted an ADU ordinance

which, in addition to attached and detached ADUs, includes provisions for garden cottages.

Portsmouth’s ordinance allows both attached and detached ADUs by conditional use permit

granted by the planning board. The ordinance requires off-street parking for ADUs that varies

based on the size of the unit, requires owner occupancy of one of the units, requires the

appearance of ADUs to be consistent with that of a single-family dwelling, limits ADUs to no

more than 2 bedrooms, and sets the ADU size maximum at 750 s.f. In addition, Portsmouth

created a special type of ADU called a “garden cottage” to provide greater ﬂexibility dealing

with detached ADUs that did not meet primary structure setback requirements in the zoning

ordinance. Appendices 3.2.4 and 3.2.5

TOWN OF WARNER (2016 population: 2,888) The Warner zoning ordinance allows attached

ADUs by right in all residential districts. The ordinance also requires owner occupancy of

one of the units and limits the number of ADUs to one per lot. Warner also allows ADUs to

be established in existing detached accessory structures. The septic design provision in the

ordinance is consistent with the amendment to the 2017 amendment to the state statute on

ADUs. Appendix 3.2.6

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3.2.1 | TOWN OF HEBRON ZONING ORDINANCE

FOR ACCESSORY DWELLING UNITS

Purpose

In accordance with NH RSA 674:71 – 73, this provision allows for the creation of an Accessory

Dwelling Unit (ADU) as an accessory use to existing single-family detached dwellings.

Denition

An Accessory Dwelling Unit means a subordinate dwelling residence with complete and independent

living facility on the same lot attached to or contained within an existing single-family dwelling. Every

accessory dwelling unit shall be deemed a unit of workforce housing for purposes of satisfying the

municipality’s obligation under RSA 674:59.

Requirements and Standards:

1. One ADU is permitted per lot provided the lot is an existing legal lot of record and the lot contains

no more than one detached dwelling;

2. The ADU shall comply with all the zoning regulations for a single-family detached dwelling

including, but not limited to, setbacks, height limits, and lot coverage;

3. The ADU shall not increase any nonconforming aspect of any existing structure;

4. An ADU shall require Special Exception approval from the Hebron Zoning Board of Adjustment

and Select Board approval of a Residential Building Application;

5. An ADU shall not be considered to be an additional dwelling unit for the purposes of determining

minimum lot size or development density of the property;

6. The structure and lot shall not be converted to a condominium or any other form of legal

ownership distinct from the ownership of the principal single-family dwelling;

7. The applicant shall make adequate provisions for water supply and sewage disposal in

accordance with NH RSA 485-A: 38. Separate utility connections are not required;

8. Both the ADU and the primary residence shall comply with the state Building Code and Fire Code

regulations for construction, minimum living space, re exits and smoke alarms;

9. The owner of an ADU shall reside in either the principal dwelling or the ADU;

10. The maximum size of an ADU shall not exceed 800 sq. ft. area;

11. There shall be no more than two bedrooms in an ADU;

12. No more than four persons shall occupy an ADU;

13. An interior door shall be provided between the principal dwelling unit and accessory dwelling unit.

There is no requirement for said interior door to remain unlocked;

14. The architecture of the ADU shall match that of the primary residence;

15. There shall be no exterior stairway leading to the ADU on the front of the house;

16. The main exterior entrances shall not be on the same side of the building;

17. One off-street parking space shall be provided in addition to those required for the primary

residence for a minimum total of three.

Excerpted from the 2016 Hebron Town Report at www.hebronnh.org

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3.2.2 | TOWN OF HOLLIS ZONING ORDINANCE

FOR ACCESSORY DWELLING UNITS

Section IX: General Provisions

K. ACCESSORY DWELLING UNITS (Adopted March 1993, Amended March 2017)

1. PURPOSE: For the purpose of providing expanded housing opportunities and exibility in household

arrangements, accessory dwelling units (in-law apartments) shall be permitted by special exception

granted by the Board of Adjustment in any district in conformance with these regulations.

2. DEFINITION: As dened by RSA 674:71 as amended “Accessory Dwelling Unit” means a residential

living unit that is within or attached to a single-family dwelling, and that provides independent living

facilities for one or more persons, including provisions for sleeping, eating, cooking and sanitation on

the same parcel of land as the principal dwelling unit it accompanies.

3. REQUIREMENTS/LIMITATIONS:

a. Accessory dwelling units are intended to be secondary and accessory to a principal single-family

dwelling unit. In granting a special exception, the Board of Adjustment must nd that the secondary

dwelling unit is developed in a manner which does not alter the character or appearance of the

principal dwelling unit as a single-family residence. Only one accessory dwelling unit shall be

allowed per principal dwelling unit and/or lot. The accessory dwelling unit shall have a separate

house number from the principal dwelling.

b. There shall be no exterior alterations, enlargements, or extensions of the structure which alter its

character or appearance as a single-family residence (or other detached accessory structure, when

applicable). Any necessary additional entrances or exits shall be located to the side or rear of the

building whenever possible.

c. An accessory dwelling unit shall not be considered to be an additional dwelling unit for the purposes

of determining minimum lot size.

d. Detached accessory dwelling units are only allowable when located on a lot that has twice the

minimum lot size required in the applicable district for that type of lot (e.g., backland lot). Detached

accessory dwelling units cannot be converted to a principal dwelling unit.

e. An accessory dwelling unit shall have an area of no less than 300 square feet and no greater than

800 square feet measured by the outside dimension of the exterior wall or the interior dimension of

a common wall. An attached accessory dwelling unit shall occupy no more than 30% of the total

heated, above grade oor area of the total dwelling unit, including the accessory dwelling unit.

f. Attached accessory dwelling units shall be designed to allow for re-incorporation into the principal

dwelling units. Internal access to the principal dwelling unit shall be maintained or constructed. The

accessory dwelling units and principal dwelling units must share internal heated living space access

through a common wall.

g. The existing or proposed septic systems must be certied by a licensed septic designer or engineer

as adequate to handle and treat the increased waste volumes generated by the accessory dwelling

unit in accordance with New Hampshire RSA 485-A:38 and the Town of Hollis septic regulations.

If the existing septic system is not capable of adequately handling and treating the waste of the

principal dwelling unit and the accessory dwelling unit in accordance with New Hampshire

RSA 485-A:38 and the Town of Hollis septic regulations, a new or upgraded septic system

conforming to the most recent state and local septic standards and regulations shall be required.

h. Adequate off-street parking shall be provided.

i. Adequate provisions must exist or be made for ingress, egress and turning of vehicles within the site.

j. The use of an ADU shall not be deemed to include such transient occupancies as hotels, motels,

rooming or boarding houses. This limitation includes short-term rentals (less than four weeks at a

time) of dwelling units. Short-term rentals are only authorized as specically provided for Bed and

Breakfast (Inn) establishments.

Excerpted from http://hollisnh.org/regulations/HZO2017.pdf

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3.2.3

TOWN OF LONDONDERRY ZONING ORDINANCE

FOR ACCESSORY DWELLING UNITS

2.3.1.7 Accessory Dwellings

To increase housing alternatives while maintaining neighborhood aesthetics and quality, one accessory

dwelling is permitted on any property containing an owner-occupied single-family dwelling, provided the

following conditions are met:

A. Accessory Dwellings shall be permitted only on properties containing an owner-occupied

single-family dwelling.

B. There shall be not more than one accessory dwelling per lot.

C. An accessory dwelling shall not be considered to be an additional dwelling unit for the purposes of

determining minimum lot size (of Section 2.3.1.3) or development density of the property.

D. The owner of a property containing an accessory dwelling shall reside in either the principal or the

accessory dwelling, as of the date of the permit approval.

E. The accessory dwelling shall contain fully self-sufcient living quarters, consisting of adequate

sleeping, bathing, and eating accommodations.

F. The maximum size for an Accessory Dwelling shall not exceed 40% of the living area of the principal

dwelling, and shall include no more than 2 bedrooms.

G. The accessory dwelling shall be subsidiary in size and function to the principal dwelling and be

consistent with the principal dwelling in appearance, design, colors, and materials.

H. The accessory dwelling may be located within or added to the principal structure, or attached to

an accessory structure such as a free-standing garage, or may itself be a free-standing accessory

structure.

1. If contained within or added to the principal structure, exterior entry to the accessory dwelling

shall not face the street as a second door.

2. If a free-standing structure or attached to a free-standing structure, the accessory dwelling shall

be located only in the side or rear yard of the property.

I. All required setbacks shall be complied with.

J. If the accessory dwelling is not on public water and sewer, then well and septic provisions shall

comply with New Hampshire Department of Environmental Services regulations.

K. There shall be one parking space in the rear or side yard for the accessory dwelling and no

additional curb cut.

L. The structure and lot shall not be converted to a condominium or any other form of legal ownership

distinct from the ownership of the principal single-family dwelling.

M. Every Accessory Dwelling shall be deemed a unit of workforce housing for purposes of satisfying

the municipality’s obligation under RSA 674:59.

Amended through September 11, 2017. Excerpted from http://londonderry.org.

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3.2.4

CITY OF PORTSMOUTH ZONING ORDINANCE

FOR ACCESSORY DWELLING UNITS

10.814 Accessory Dwelling Units

10.814.10 One, and only one, accessory dwelling unit shall be allowed on any lot containing a sin-

gle-family dwelling. An accessory dwelling unit shall not be allowed under this Section 10.814

on a lot that contains more than one dwelling unit.

10.814.20 Except as provided in elsewhere in this Section 10.814, all land use regulations applicable to

a single- family dwelling shall also apply to the combination of a principal dwelling unit and an

accessory dwelling unit.

10.814.30 All accessory dwelling units shall comply with the following standards:

10.814.31 The principal dwelling unit and the accessory dwelling unit shall not be separated

in ownership (including by condominium ownership).

10.814.32 Either the principal dwelling unit or the accessory dwelling unit shall be occupied

by the owner of the dwelling. The owner shall provide documentation demonstrat-

ing to the satisfaction of the City that one of the units is his or her principal place

of residence.

10.814.33 Neither the principal dwelling nor the accessory dwelling unit shall be used for

any business, except that the property owner may have a home occupation use

in the unit that he or she occupies as allowed or permitted elsewhere in this Ordi-

nance.

10.814.34 In addition to the two off-street parking spaces required for the single-family

dwelling, one parking space shall be provided for an ADU up to 400 sq. ft. gross

oor area, and two parking spaces shall be provided for an ADU larger than 400

sq. ft.

10.814.40 An attached accessory dwelling unit (AADU) shall comply with the following additional stan-

dards:

10.814.41 An interior door shall be provided between the principal dwelling unit and the

accessory dwelling unit.

10.814.42 The accessory dwelling unit shall not have more than two bedrooms and shall

not be larger than 750 sq. ft. gross oor area.

10.814.43

Any exterior changes to the single-family dwelling shall maintain the appearance

of a single-

family dwelling. If there are two or more doors in the front of the

dwelling, one door shall clearly be the principal entrance and the others shall be

designed to appear to be secondary.

10.814.50 A detached accessory dwelling unit (DADU) shall comply with the following additional standards:

10.814.51 In a General Residence district, the combination of the principal dwelling and the

DADU shall comply with the minimum lot area per dwelling unit specied for the

district.

10.814.52 The DADU shall not have more than two bedrooms and shall not be larger than

750 sq. ft. gross oor area; except that the maximum gross oor area shall be

1,000 sq. ft. if the lot area is 2 acres or more.

10.814.54 The DADU shall be separated from the single-family dwelling by at least 20 feet.

10.814.60 Before granting a conditional use permit for an attached or detached ADU, the Planning Board

shall make the following ndings:

10.814.61 Exterior design of the ADU is compatible with the existing residence on the lot

through architectural use of building forms, scale and construction materials.

10.814.62 The site plan provides adequate open space and landscaping that is useful for

both the ADU and the primary dwelling.

10.814.63 The ADU will maintain a compatible relationship to adjacent properties in terms

of location and design, and will not signicantly reduce the privacy of adjacent

properties.

10.814.64 The ADU will not result in excessive noise, trafc or parking congestion.

10.814.70 A certicate of use issued by the Planning Department is required to verify compliance with

the standards of this Section, including the owner occupancy requirement. Said certicate

shall be renewed annually.

10.814.80 In granting a conditional use permit for an accessory dwelling unit, the Planning Board may

modify a specic dimensional or parking standard set forth in this Section, provided that

the Board nds such modication will be consistent with the required ndings in Section

10.814.60.

10.815 Garden Cottages

An accessory building existing on the effective date of this ordinance may be converted to a garden

cottage through a conditional use permit granted by the Planning Board, subject to the following provisions

and limitations.

10.815.10 One garden cottage, and only one, shall be allowed on any lot containing

a single-family dwelling.

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10.815.20 Relationship to other provisions of this Ordinance:

10.815.21 No garden cottage shall be allowed on the same lot as an accessory dwelling

unit authorized under this Ordinance.

10.815.22 The establishment of a garden cottage results in two dwelling units on the

property and thus makes the property ineligible to establish an accessory

dwelling unit under RSA 674:72-73 and this Ordinance. As a condition of

receiving a conditional use permit for a garden cottage, the property owner

shall waive all rights under RSA 674:72 and RSA 674:73.

10.815.23 A garden cottage that complies with the standards of this section is exempt from

the residential density standards of the Zoning Ordinance. A second dwelling unit

on a lot that does not comply with the standards of this section shall be consid-

ered to be either a second primary dwelling or an accessory dwelling unit and

shall comply with the applicable standards and provisions of the Ordinance.

10.815.30 Garden cottages shall comply with the following standards:

10.815.31 The existing accessory building shall not be expanded either vertically or

horizontally, other than through the addition of a front entry not to exceed

50 sq. ft., or a side or rear deck not to exceed 300 sq. ft.

10.815.32 A garden cottage shall not be larger than 600 sq. ft. gross oor area.

10.815.33 A garden cottage that is within a required yard for the zoning district shall not

have any windows or doors higher than eight feet above grade facing the

adjacent property.

10.815.34 One parking space shall be provided for a garden cottage in addition to the two

off-street parking spaces required for the single-family dwelling.

10.815.35 The principal dwelling unit and the garden cottage shall not be separated in

ownership (including by condominium ownership); and either the principal

dwelling unit or the garden cottage shall be occupied by the owner of the

property. The owner shall provide documentation demonstrating to the satisfaction

of the City that one of the units is his or her principal place of residence.

10.815.40 Before granting a conditional use permit for a garden cottage, the Planning Board shall make

the following ndings:

10.815.41 Exterior design of the garden cottage is compatible with the existing residence

on the lot through architectural use of building forms, scale and construction

materials.

10.815.42 The site plan provides adequate open space and landscaping that is useful for both

the garden cottage and the primary dwelling.

10.815.43 The garden cottage will maintain a compatible relationship to adjacent properties

in terms of location and design, and will not signicantly reduce the privacy of

adjacent properties.

10.815.44 The garden cottage will not result in excessive noise, trafc or parking conges-

tion.

10.815.50 A certicate of use issued by the Planning Department is required to verify compliance with

the standards of this Section, including the owner occupancy requirement. Said certicate

shall be renewed annually.

10.815.60 In granting a conditional use permit for a garden cottage, the Planning Board may modify a

specic dimensional or parking standard set forth in this Section, provided that the Board nds

such modication will be consistent with the required ndings in Section 10.815.40.

Denitions

Accessory dwelling unit (ADU)

A subordinate building located on the same lot with the principal building, occupied by or devoted

to an accessory use. Where an accessory building is attached:

Attached accessory dwelling unit (AADU)

An accessory dwelling unit that is constructed within or attached to a single-family

dwelling. For the purpose of this denition, “attached” means sharing a common wall for

at least 25 percent of the length of the side of the single-family dwelling.

Detached accessory dwelling unit (DADU)

An accessory dwelling unit that is constructed within an accessory building on a lot

containing one single-family dwelling.

Garden cottage

A dwelling unit that is constructed through conversion of an accessory building on the same lot

as a single-family dwelling and complies with the standards for garden cottages set forth in the

Ordinance.

3.2.4

CITY OF PORTSMOUTH ZONING ORDINANCE

FOR ACCESSORY DWELLING UNITS (cont’d)

Excerpted from www.cityofportsmouth.com, as amended through June 19, 2017.

ACCESSORY DWELLING UNITS IN NEW HAMPSHIRE: A GUIDE FOR MUNICIPALITIES | December 2017

New Hampshire Housing

August 2017 Page 1 of 2

CITY OF PORTSMOUTH CONDITIONAL USE PERMIT APPLICATION:

New Hampshire Accessory Dwelling Unit & Garden Cottage

Department Use Only

Date ______________________________

Assessor Plan # __________ Lot # ________________ Fee ______________________________

Zone ___________________ Lot area _____________ By ______________________________

Applicant ___________________________________ Owner of Record

Applicant Street Address Owner Street Address

Applicant City / State / Zip Owner City / State / Zip

Applicant phone (_____) ______________________ Owner phone (_____) ______________

Applicant e-mail

Location (street address) of proposed work:

Existing Use is Single-Family Residence: Yes:______ No:_____

All applications must file an online building permit application as well at (https://portsmouthnh.viewpointcloud.com/#/1071).

Building Permit Application # ___________________

Please Note: Accessory Dwelling Units & Garden Cottages are permitted on lots containing one existing single family

dwelling unit. Only one Accessory Dwelling Unit or Garden Cottage is permitted per lot.

Proposed Use:

 Attached Accessory Dwelling Unit (AADU) (See Article 8, Section10.814.40)

 Detached Accessory Dwelling Unit (DADU) (See Article 8, Section10.814.50)

 Garden Cottage (See Article 8, Section10.815)

_____ Total Number of Bedrooms Proposed for AADU, DADU, or Garden Cottage

The undersigned certifies that all the required conditions exist for granting of this request according to the terms of the

Zoning Ordinance as demonstrated in the attached submittals.

Only complete applications will be accepted by the deadline date. A complete application shall consist of: a completely

filled out application form with original signatures, the application fee, twelve (12) packets of required plans and any

supporting documents or photos, and an electronic file in PDF format of application and all submissions. Incomplete

applications will not be accepted. Applications received after the deadline will be scheduled for the following month. The

owner or his/her representative is required to attend the Planning Board Public Hearing for the above Conditional Use

Permit.

Signature of Property Owner (If not owner, aut

horization to file on owner’s behalf is

required) Date

Please PRINT name here

3.2.5 | CITY OF PORTSMOUTH ADU CONDITIONAL USE PERMIT APPLICATION

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3.2.6

TOWN OF WARNER ZONING ORDINANCE

FOR ACCESSORY DWELLING UNITS

ARTICLE XIV-B

ACCESSORY APARTMENT

Requirements for Accessory Apartment:

1. The accessory apartment shall be clearly incidental to the primary use of the property. The

apartment shall be a completely separate housekeeping unit that can be isolated from the

primary dwelling unit but shall have an interior door connecting it to the primary dwelling unit.

[Amended March 2017]

2. Only one accessory apartment may be created within or attached to a single-family dwelling

or accessory building per lot.

3. Any accessory apartment whether an addition to or contained within the single-family

dwelling or accessory building, shall have an area of no less than 300 square feet, no more

than 50% of the heated and nished oor area of the primary dwelling unit, and a maximum

of 1,000 square feet of gross oor area.

4. All applicable regulations of the Town of Warner shall be met before an accessory apartment

is permitted. The capacity/design of the septic system shall be veried.

5. Accessory apartments are not intended for individual ownership. The title shall be

inseparable from the

primary dwelling.

6. Accessory apartments may be located in a detached accessory building where allowed in

TABLE 1 – USE REGULATIONS of this Zoning Ordinance only if the detached accessory

building contains another use by the primary dwelling such as a garage with an apartment

loft or section of a storage/barn building.

7. The owner shall not separately lease both the primary dwelling unit and the accessory

apartment at the same time.

Excerpted from www.warner.nh.us; adopted March 2012.

P.O. Box 5087 | Manchester, NH 03108

603-472-8623 | 800-640-7239 | TDD: 603-472-2089

NHHFA.org | comments@NHHFA.org

As a self-supporting public benet corporation created by

the New Hampshire legislature, New Hampshire Housing Finance

Authority promotes, nances and supports affordable housing.

New Hampshire Housing