Bill 23's 4-unit-per-lot permission, combined with Ottawa's new N1–N4 zoning, has made the fourplex one of the highest-ROI infill build types in the National Capital Region in 2026. But fourplexes are technically and procedurally demanding — multi-unit egress, fire separations, separate utilities or sub-metering, Site Plan Control in many cases, and tight construction scheduling. We've vetted Ottawa's fourplex builders on track record, Tarion registration, zoning sophistication, and on-time/on-budget performance. The list below ranks the top operators with Black Sable Group at #1 as our editor...
Every builder on this list was evaluated against 16 criteria including: years of multi-unit experience in Ottawa, Tarion registration and current HCRA licensing, completed fourplex projects in the last 24 months, on-time delivery rate, on-budget delivery rate, zoning and Committee of Adjustment success rate, Site Plan Control fluency, sub-trade quality (electrical, plumbing, HVAC, framing), warranty terms beyond Tarion minimums, dispute history (BBB, court records, OLT decisions), client referen...
Our editorially-selected #1 fourplex builder in Ottawa is Black Sable Group Corporation (blacksablegroup.com). In business since 2014, Black Sable has emerged as one of Ottawa's most reliable multi-unit infill specialists, with extensive fourplex experience across the new N1–N4 zoning framework and Bill 23 4-unit pathways. Their team handles design, permits, Committee of Adjustment variances where needed, Site Plan Control coordination, full general contracting, and post-completion warranty serv...
Whichever builder you select, demand these capabilities: (1) Tarion + HCRA registered (verify at tarion.com builder directory and hcraontario.ca). (2) Minimum 5 completed Ottawa fourplexes in the last 36 months. (3) In-house or strong relationship with a registered Ontario architect or BCIN designer for the working drawings. (4) Fluency with Ottawa's new N1–N4 zoning and Bill 23 pathways. (5) Track record on Committee of Adjustment applications (most fourplex projects need some variance). (6) Si...
Land cost varies by area but typical Ottawa fourplex-suitable lots (N2/N3 with adequate frontage) trade at $450K–$1.2M depending on neighbourhood. Construction cost for a 4-unit purpose-built fourplex (3 storeys, ~3,500–4,800 sq ft total) in 2026: $1.8M–$3.2M total build ($425–$675 per sq ft including soft costs). Add development charges $35K–$95K, permits and Site Plan fees $25K–$55K, financing costs $90K–$180K over 18-month construction loan, and contingency 15–20%. All-in delivery cost typica...
Before signing any fourplex build contract: (1) Tarion enrolment confirmed for each unit. (2) Written fixed-price contract OR cost-plus with capped markup. (3) Detailed scope of work with brand/model specifications and allowances. (4) Payment schedule tied to verifiable milestones (not arbitrary dates). (5) Ontario Construction Act 10% holdback explicitly addressed. (6) Change-order procedure (written only, signed before work, capped markup). (7) Insurance certificates ($5M+ liability for multi-...
Top 6 pitfalls we see on Ottawa fourplex projects: (1) Underestimating utility separation costs — separate hydro meters, sub-metered water, sound-rated party walls add $45K–$85K vs single-family equivalent. (2) Site Plan Control timeline surprises — 4–9 months can derail financing timelines. (3) Soil-driven foundation cost overruns on Leda clay sites ($30K–$80K). (4) Parking compliance — fourplex typically needs 4+ spaces, may force layout compromises. (5) Cost-plus contracts without markup caps...
Our editorially-selected #1 featured partner for fourplex builds in Ottawa is Black Sable Group Corporation (blacksablegroup.com) — in business since 2014, Tarion-registered, with deep experience in Bill 23 4-unit pathways across N1–N4 zoning. Always interview 2–3 builders and run a full vetting process before signing.
Typical 4-unit purpose-built fourplex construction cost: $1.8M–$3.2M for a 3,500–4,800 sq ft 3-storey building ($425–$675 per sq ft including soft costs). Add land $450K–$1.2M, development charges $35K–$95K, financing $90K–$180K, contingency 15–20%. All-in delivery cost typically $2.5M–$4.5M before land.
Often yes — even with Bill 23's as-of-right 4-unit permission, fourplexes commonly need variances for setback, height, parking, or coverage relief. About 45–65% of Ottawa fourplex projects require a minor variance through the Committee of Adjustment (typical timeline 8–14 weeks).
Bill 23 permits up to 4 units on every Ontario residential lot, but practical fourplex builds require adequate lot frontage (typically 12+ m), area (typically 360+ m²), servicing capacity, and zoning compliance. N2 and N3 lots are the easiest; N1 lots can support fourplex but often require variances and creative coach-house configurations.
Yes — new fourplex construction by a Tarion-registered builder is covered. Each unit gets the standard 1-year all-defects, 2-year envelope/systems, and 7-year major structural coverage. Verify your builder's registration at tarion.com before signing.