Single to Multi-Family Conversion FAQs

Start with an informal visit to the Planning Board as early in the process as possible:

• You don’t need a detailed design, or any design at all
• They will have to sign off on your site plan anyway
• They can answer many of your questions
• You can contact the Board’s chair and ask for time at a meeting or simply show up at a meeting (in person or online) and ask your questions during the time slot set aside for that

You will need to comply with the usual departments and boards:

• Conservation Commission – clarification about when ConComm gets involved
• Board of Health – must verify your septic can support the ADU’s bedroom(s)
• Building Department  – you or your contractor need to complete applications and receive the applicable (building, wiring, plumbing) permits
• Planning Board – you will need to apply for a site plan review: Site Plan Review Application

Here’s some online help:

• Site Plan Review Application

Entrances

• Only one entrance per façade unless each entrance is on its own ell or wing
• The units may also share an entrance from a common foyer/hallway

Driveways

Only one driveway is permitted.

Exterior staircases

Not allowed above the first floor.

Parking

2 spaces per unit.

Setbacks

50 feet from lot lines and from street right-of-way.

Yes.

No. You cannot substantially enlarge the exterior of the pre-existing dwelling. However:

• You can re-purpose any space within the exterior
• You can add exterior features (wrap around porch) that exceed the original footprint

To be eligible for conversion, your home must be:

• Constructed on or before 1980
• Have at least 3 acres exclusive of wetlands to convert to a two-family home
• Have at least 5 acres exclusive of wetlands to convert to a three-family home

See section whatever of Princeton’s zoning by-laws.

Conversion enables residents with large homes on larger parcels to remodel their one-family home into a two-family or three-family home.