How much does a bump-out addition cost compared to a full addition in NB?

A bump-out addition in New Brunswick typically costs $15,000–$60,000 for a small targeted expansion of 50–150 sq ft, compared to $100,000–$200,000 for a full addition of 300–500 sq ft — but the per-square-foot cost of a bump-out is often higher than a full addition because the fixed costs of foundation, roofing, and trade coordination are spread over fewer square feet.

A bump-out is a targeted, purposeful expansion of a specific room — extending a kitchen by four feet to create room for an island, widening a bathroom to fit a walk-in shower, or pushing a dining room out 6 feet to add seating for a larger family. The appeal is obvious: you solve a specific problem without the disruption and cost of a full-scale addition. And in the right circumstances, a bump-out delivers excellent value.

Here's what makes bump-out costs more nuanced than they first appear. Every addition — even a 6-foot extension of a kitchen — requires a proper foundation below NB's frost line. That foundation work, combined with a new roof section, exterior cladding to match your existing home, a new floor assembly over the new space, and the inevitable plumbing, electrical, or structural work triggered by opening up the exterior wall, means the fixed cost floor for any bump-out is roughly $15,000–$25,000 regardless of how small the extension is. For a 50–80 sq ft bump-out, those fixed costs represent $200–$400+ per square foot before you've added a single finish.

Contrast that with a full 400 sq ft addition, where those same foundation, roofing, and trade coordination costs are spread over four or five times the floor area, bringing the per-square-foot cost down into the $250–$350 range. If you're already doing the foundation, roofing, and trade work, the incremental cost of additional square footage is meaningful but not dramatic.

That said, bump-outs make excellent financial sense in several specific NB scenarios. If your home's main floor layout has one room that's chronically too small and fixing that problem will make the home significantly more functional — a kitchen that can't fit a dishwasher, a bathroom that forces renovation because the tub can't be removed without structural work, a bedroom too narrow to fit a queen bed — the targeted cost of a bump-out is far less than the disruption and cost of moving. Bump-outs are also the right tool when you don't have lot area or setback clearance for a full addition but do have room for a modest 4–6 foot extension on one wall.

NB-specific considerations: the foundation for any bump-out must go below the 4–5 foot frost depth, exactly like a full addition. Cantilevered bump-outs (extending the floor framing without a new foundation, for second-floor expansions over a deck or garage, for example) are a structural solution that eliminates the foundation cost, but they require proper engineering to avoid deflection problems and must be insulated carefully to prevent cold floors — a real issue in NB winters.

Get a quote for both options — a targeted bump-out and a more substantial addition — before deciding. You may find the gap is smaller than you expect once the fixed costs of the bump-out are laid out, and the larger space may be the smarter long-term investment. Experienced NB contractors will walk you through this comparison honestly.

---

Looking for experienced contractors? The New Brunswick Construction Network connects homeowners with qualified professionals:

• Gionetterenovations
• Thirty Four Renovations