Multiplex Conversion (2-4 Plex) in Ajax

Smaller 2-unit basement legalization or duplex: $100K–$250K. 3-unit conversion (basement + two main-floor): $250K–$500K. Full 4-unit conversion with structural changes and additions: $500K–$1M. New-build multiplex (tear-down + new): $700K–$1.5M for a 3,000 sq ft 4-unit, $350–$550/sq ft. Cost depends heavily on existing structure (underpinning needs, electrical capacity, basement head height), scope (egress changes, kitchens, structural beams), and finish level.

Bylaw 474-2023 (May 10, 2023) permits up to 4 units (duplex, triplex, fourplex) on every lot in RD, RS, and RT residential zones in Ajax, with built-form standards similar to detached houses. Maximum height up to 10 m where existing zoning permits. Up to two porches/decks/balconies per unit. No parking minimums (removed city-wide February 2022). Front-entrance restrictions for secondary suites deleted. Multiplexes can be conversions OR new construction. This bylaw effectively ended single-family-only zoning in Ajax.

Bill 23 (More Homes Built Faster Act, 2022) requires every Ontario municipality to permit up to 3 ARUs per lot as-of-right where servicing is available, removes parking minimums for ARUs, and reduces or eliminates development charges for ARUs. Ajax exempts the 3rd and 4th units from development charges entirely under 474-2023. Bill 23 also reduces planning fees and conservation authority approvals. The 5th unit (and beyond) triggers standard DCs of ~$45K–$55K per unit.

Ontario Building Code requires 45-minute fire separation between dwelling units (Type 1 or Type 2 assembly per OBC 9.10.9) — typically achieved with double-layer 5/8" Type X gypsum drywall on resilient channels with mineral wool or rockwool insulation in stud cavities. Fire-rated doors (20-min minimum) on demising walls. Smoke and CO alarm interconnection across all units per OBC 9.10.19. Sound transmission control STC ≥ 50 between units per OBC 9.11. Each unit needs independent egress per OBC 9.9 — usually separate exterior doors.

Often, yes — required when basement ceiling height is less than 6'5" (1.95 m), the OBC minimum for habitable rooms. Underpinning lowers the basement floor by excavating and pouring new footings deeper than the existing foundation; typical scope adds $30K–$80K to project cost depending on perimeter and foundation type (concrete vs. stone vs. brick). Many older Ajax homes (pre-1950) have head heights of 6'2"–6'4" and require underpinning to legalize a basement unit.

Almost always yes. Full-scope structural changes, demising wall additions, and major mechanical work cannot be done with tenants in place — both for safety reasons and because the existing units rarely match the new floor plan. Vacant possession during construction is the homeowner's responsibility (Landlord and Tenant Board procedures, N12/N13 notices, compensation). RenoHouse does NOT represent landlords at the LTB — please consult a paralegal or landlord-tenant lawyer for that scope.

CMHC MLI Select is a multi-unit residential mortgage insurance program for 5+ unit rental properties. Benefits: up to 95% loan-to-value (5% down), up to 50-year amortization (with surcharge), and forgivable energy-efficiency grants up to $85K/unit for NZE-ready builds. Ajax strategy: convert main house to fourplex (4 units) + add garden or laneway suite (1 unit) = 5 units → eligible for MLI Select. We deliver the construction; we do NOT arrange financing — refer to your mortgage broker for MLI Select structuring.

2-unit basement legalization or duplex: 4–8 months. 3-unit conversion: 6–12 months. Full 4-unit conversion with structural changes: 12–18 months. New-build multiplex (tear-down + new construction): 14–24 months. Permit drawings 6–10 weeks; plan review 8–14 weeks (longer than ADUs because Building Department reviews multi-unit OBC compliance more carefully); construction 16–40 weeks depending on scope.

Ajax 2026 rents per unit: 1BR basement (after underpinning) $1,500–$2,200/month, 1BR main-floor $1,800–$2,500/month, 2BR upper-floor $2,500–$3,200/month, 2BR penthouse $2,800–$3,500/month. Total gross rent on a typical 4-plex: $7,500–$11,000/month. After vacancy, operating expenses, and maintenance reserve, NOI on a $1.05M total-cost build (acquisition + conversion) typically $65K–$85K/yr — a 4.5–5.5% cap rate (Ajax market-typical). Cash-on-cash with 95% MLI Select financing can reach 12–18%.

Yes — we have HCD project experience in Cabbagetown, Riverdale, and the Annex. HCD multiplex conversions require a Heritage Permit alongside the building permit; exterior alterations must be compatible with the district's character. Some major scope items (rear additions, third storey additions, exterior staircases for egress) may not be approvable in HCDs and need to be redesigned. Heritage Permit adds 4–8 weeks and design adjustments. We work with designers familiar with each Ajax HCD.