Home additions in Ottawa cost $295-$525 per square foot in 2026 depending on type, foundation work, and finish level. This guide breaks down second-storey, rear, side, and bump-out addition costs with realistic 2026 Ottawa pricing, permit requirements, and ROI data.
Rear addition (single-storey, new foundation): $325-$475/sq ft. Rear addition (two-storey, new foundation): $295-$425/sq ft (cheaper per sq ft due to shared foundation). Side addition: $325-$485/sq ft (often more expensive due to access constraints). Second-storey addition (over existing main floor): $385-$525/sq ft (structural reinforcement of existing foundation often needed). Bump-out (4-8 ft extension, often cantilevered): $415-$625/sq ft. Garage addition (detached): $185-$285/sq ft. Garage ...
200 sq ft bump-out: $80K-$125K. 400 sq ft single-storey rear: $130K-$190K. 600 sq ft single-storey rear: $195K-$285K. 800 sq ft two-storey rear: $235K-$340K. 1,000 sq ft two-storey rear (master suite up, family room down): $295K-$425K. 1,200 sq ft full second storey: $460K-$630K. 600 sq ft 4-season sunroom: $230K-$335K.
Building permit: $15.50/$1,000 of construction value ($1,500-$8,000 typical). Engineering stamp (structural): $1,800-$4,500. Architect drawings (if required): $4,500-$18,000 depending on scope. Committee of Adjustment (for any setback or coverage variances): $1,200-$2,500 in filing fees + 4-6 month timeline. Heritage approval (heritage districts): +$500-$2,000 + 2-4 month timeline. Conservation Authority (for waterfront/regulated areas): $500-$2,500.
Foundation work in clay-rich Leda zones (Orleans, Vanier, parts of Nepean): $15K-$45K premium for engineered foundation systems. Removing/rebuilding existing exterior wall: $8K-$25K. Roof tie-in complexity (joining new addition roof to existing): $5K-$25K. Matching existing siding/brick (especially older brick): $8K-$35K premium for custom-matched material. HVAC capacity upgrade (existing system can't handle new load): $5K-$18K. Electrical service upgrade if you're maxing existing 100A panel: $3...
Master suite addition: 60-75% ROI on resale. Family room rear addition: 55-70% ROI. Kitchen expansion: 75-95% ROI. Mudroom/laundry bump-out: 65-85% ROI. Second storey full add: 60-80% ROI (varies more with neighbourhood). Garage addition (attached): 75-95% ROI. Sunroom (4-season): 45-65% ROI. Best ROI: anything that adds standard bedroom/bathroom count in a neighbourhood where comparable homes have more bedrooms (e.g., 2-bed to 3-bed in Westboro).
2026 ranges: rear addition $295-$475/sq ft, side $325-$485/sq ft, second-storey $385-$525/sq ft, bump-out $415-$625/sq ft. Total: 200 sq ft bump-out $80K-$125K; 1,000 sq ft two-storey rear $295K-$425K.
Always yes. Building permit, plumbing/electrical/HVAC permits, engineering stamp, possibly architect drawings, possibly Committee of Adjustment if setbacks or lot coverage are affected, heritage permit if applicable.
Permits + design: 4-8 months (longer with Committee of Adjustment). Construction: 16-32 weeks depending on size. Total typical timeline: 10-16 months from initial design to completion.
Best ROI: kitchen expansion 75-95%, mudroom/laundry bump-out 65-85%, attached garage 75-95%, master suite 60-75%. Lower ROI: 4-season sunrooms (45-65%) and second-storey full adds (60-80%, neighbourhood-dependent).
Per sq ft: second-storey is more expensive ($385-$525) due to structural reinforcement of existing foundation. But it preserves backyard space and doesn't trigger lot-coverage limits — making it the only option on many smaller Ottawa lots in Centretown, Old Ottawa South, and Westboro.