How much does in law suite addition cost in New Brunswick?

Adding an in-law suite in New Brunswick typically runs $80,000–$250,000+ depending on the type, size, and location — a wide range that reflects very different approaches to the project.

The most affordable route is a basement conversion, where you're finishing existing space and adding a separate entrance. Expect $80,000–$130,000 for a well-done basement suite with proper egress windows, a kitchenette, bathroom rough-in, and fire separation. A main-floor addition (building new square footage onto the house) jumps considerably — $150,000–$250,000+ is realistic once you factor in foundation work, framing, roofing, and full mechanical systems. A detached garden suite or accessory dwelling on the same property sits in the $180,000–$300,000+ range, since it's essentially a small house with its own foundation, utilities, and separate connections.

What drives the cost up in NB

Labour shortages in the trades — particularly plumbers and electricians — can stretch timelines and add cost, especially in rural areas and northern communities like Edmundston or Campbellton. Material costs have stabilized somewhat since the 2021–2022 spike but remain elevated. Older homes (1970s–1990s bungalows are extremely common in Riverview, New Maryland, and Quispamsis) often reveal surprises: knob-and-tube wiring, asbestos, failing weeping tile, or undersized electrical panels that need upgrading before suite work can begin.

The permit picture matters a lot here

In-law suites require a building permit — from your municipality if you're in Moncton, Fredericton, Saint John, or another incorporated city, or from your Regional Service Commission if you're in a rural or unincorporated area. Zoning is the first hurdle: secondary suites are permitted in many NB residential zones, but rules vary significantly. Fredericton and Moncton/Dieppe are generally suite-friendly; Saint John varies by neighbourhood. Contact your local planning office before drawing up plans.

Under the National Building Code of Canada 2020 (mandatory for new applications as of May 1, 2025), a secondary suite requires a minimum ceiling height of 1.95m (6'5"), a 45-minute fire separation between units, interconnected smoke and CO alarms, egress windows in every bedroom, and a separate heating system or fire-rated ductwork. These aren't optional — inspectors will check every item.

All electrical work requires a licensed electrical contractor and a wiring permit through NB Power (1-800-615-0522). Plumbing and gas work must be done by tradespeople licensed through NB's Technical Inspection Services (TIS) at 1-888-659-3222. These aren't areas where you can cut corners — unpermitted suites create serious insurance and liability problems, and they can complicate a future home sale significantly.

A practical note on budget

Budget a 15–20% contingency on top of your contractor quotes — older NB homes almost always have hidden costs once walls open up. Get at minimum three quotes from licensed general contractors, and ask each one specifically about their experience with secondary suite projects and local permit processes.

Your best first step is a pre-consultation with your municipal planning department or RSC to confirm zoning compliance and get a sense of permit requirements before spending money on drawings. From there, browse licensed contractors in the New Brunswick Construction Network directory to find professionals experienced with suite additions in your area.