Multiplex Conversion Toronto in Whitby

Up to 4 dwelling units within a single primary building (the multiplex) plus optionally 1 additional garden suite or laneway suite for a total of 5 units. This was unlocked by Whitby City Council in May 2023 (By-law 287-2023) following the provincial Bill 23 mandate. The 5-unit stack play is the canonical setup for CMHC MLI Select financing.

Multiplex up to 4 units is as-of-right across all Whitby R-zones — no rezoning, no Committee of Adjustment required if the work stays within the existing building envelope. COA is only triggered by additions exceeding zone height/setback or by a 5+ unit project.

CMHC MLI Select is a federal mortgage insurance program for rental properties with 5+ units (in some product variants, 4+). It enables 50-year amortization, 95% loan-to-value, and near-prime interest rates in exchange for affordability, energy-efficiency, or accessibility commitments. For a Whitby fourplex-plus-garden-suite, MLI Select typically saves $1,800 to $3,500/month in debt service compared to a conventional mortgage.

Plan for 12 to 18 months from first call to last tenant move-in. Design and permit phase is 5 to 7 months (longer if COA or Site Plan triggered). Construction is 6 to 10 months. Inspections and occupancy add 3 to 5 weeks. Projects without addition (existing envelope only) compress to 10 to 12 months.

Acoustic non-compliance is the most common late-stage cost shock. Existing dimensional-lumber floors test at STC 35 to 40; OBC 9.11 mandates STC 50 between dwellings. Properly retrofitting an existing floor-ceiling assembly (resilient channel + Type X + acoustic batt + underlay) can cost $18 to $35 per sq ft. Designing this in from day one is much cheaper than fixing it after drywall.

Not legally required, but strongly recommended. Whitby Hydro will install separate meters for $1,800 to $4,200 per additional service at conversion time; doing this later requires service interruption and re-permitting. Tenant-billed hydro reduces landlord operating cost variance and is a near-universal expectation in 2026 leases.

Yes, but the property must be rewritten as small-multi-unit commercial residential. Standard home insurers (TD, Allstate, Belair) typically transfer the policy to their commercial subsidiaries. Premium runs $2,800 to $4,800/year for a fourplex versus $1,400 to $2,200 for the prior single-family. Disclose at occupancy — failure to disclose voids coverage.

No. A multiplex up to 4 units remains in the residential R-zone under By-law 569-2013. Property tax classification stays residential for properties under 7 units. The multiplex is a residential use of land, distinct from apartment buildings (Part 3 OBC, commercial property tax).