ADUs in Princeton, NJ
WHAT ARE ADUS?
ADUs (Accessory Dwelling Units) are self-contained structures, with a size limitation of ∼800 sq. ft. (see below), that share a single-family lot with a larger, primary dwelling. They can either be embedded, attached, or detached (see below graphic). ADUs have gained popularity in the recent years as more people hope to stay in Princeton with their family, or relocate to the Princeton area. An ADU can be converted from an existing structure (such as a garage) or built anew. This type of building supports efficient use of existing housing stock and infrastructure and provides sustainable housing options that respond to changing family needs, smaller households, and increasing housing costs. ADUs can also provide a great option for older residents to remain in their community and “age-in-place” (wheelchair accessible options are incentivized).
ADU used for residential and/or occupational purposes
Space limited to residents solely
No exterior indication of home occupation allowed
Max. of 1 ADU per lot
Max. size is 800 sq. ft. or 25% of the total floor area of the primary dwelling unit, whichever is greater
*Exception for handicapped accessible, granted an increase of 5% of the total floor area applied to either primary dwelling or ADU, or both (New Jersey’s Barrier Free sub-code)
Max. height is 20 ft. or height of primary dwelling unit, whichever is less.
No minimum lot size requirement
*Specific setback and lot coverage requirements of the district will apply
Side or rear yard location exclusively
Max. of 3 habitable rooms per ADU
No additional off-street parking for ADU with 2 habitable rooms
One additional off-street parking space for ADU with 3 habitable rooms
In Princeton, ADUs can be constructed as embedded (within the main house), attached (via an addition), or detached (a garage conversion or built anew).
WHERE CAN ADUS GO IN PRINCETON?
ADUs are a permitted accessory use in all single-family residential districts (R-A through R-H), either as part of a primary dwelling or a separate accessory structure on the same lot. They can be a vital tactic for increasing housing in a town with high real estate prices and property taxes, as well as a lack of land for new development. Their small scale optimizes space while not detracting from the existing neighborhood. Less average space per person and smaller associated carbon footprints makes ADU development an environmentally-responsible housing choice.
*Click here for a link to Princeton’s zoning map to find out which residential district you are in
BRIEF HISTORY OF ADUS IN PRINCETON
The most recent change to local ordinance ( #2020-16) eliminates the requirement for the owner of the property to occupy one of the units. This permits the sale of both the primary dwelling and the ADU to separate people, if the property owner chooses to do so.
The demand for ADU design and construction is prevalent in several municipalities throughout NJ, but has yet to become a statewide standard. Fairly quick approval processes (compared to that of large-scale apartment complexes) makes ADUs a favored form of development. This type of development requires us to think strategically and leverage the resources available. It also provides an opportunity for homeowners to have more choice in how they use their property, while ensuring dignity and privacy for the ADU inhabitants.
BUILDING YOUR PROJECT
Building an ADU involves three phases:
Consult: MDB will evaluate your property for suitability for construction of an ADU.
*Requirements: You will need to provide a stamped survey of your property that is less than 10 years old (we can provide references for potential surveyors on request).
Design: We will create a custom solution that meets your needs be it for aging in place, live-in help, multi-generational living, etc.
*Coordinate with a civil engineer to obtain municipal approvals
*Provide a cost estimate for construction of the project
Construction: Our trusted network of sub-contractors and professionals help us to provide consistently beautiful results on time and on budget.
*Our building practices focus on energy efficiency and low embodied carbon (i.e., low VOC (volatile organic compound) materials, triple-pane windows and doors, heat recovery and ventilation, etc.)
*Download an ADU Guide in pdf format here.