For years, investors were stuck choosing between a fourplex that doesn’t move the needle and a mid-rise that needs a development team, a decade of patience and a balance sheet to match. The 10-unit, 3-storey building sits in the sweet spot between the two. It’s big enough to change your portfolio, and small enough to design, permit and build without the machinery of a large development.
Why “10 Units” Is the Magic Number
Since Bill 23 (2022), the Planning Act exempts residential development of 10 units or fewer from site plan control. There are carve-outs: lands within 120 metres of a shoreline or 300 metres of a railway line can still be pulled back in by the municipality. Outside those areas, a 10-unit residential building generally goes straight from zoning compliance to building permit.
That’s the single biggest reason this strategy works. Add an 11th unit, and you’re into site plan approval: more consultants, more studies, a site plan agreement, securities and often 6 to 18 months of extra process.
Why “3 Storeys” Matters Just as Much
Keep the building to 3 storeys and a building area of 600 m² or less, and it typically falls under OBC Part 9 instead of Part 3. That changes the whole project:
- Simpler code path. Part 9 is prescriptive and well understood by designers, examiners, inspectors and contractors.
- Wood-frame construction. Conventional lumber, engineered joists and trusses. Minimal steel — often just a few beams or lintels where spans demand it.
- No elevator required. A Part 9 residential building of up to 3 storeys generally doesn’t need an elevator. That saves the equipment cost, the shaft and machine space, and years of maintenance and inspection fees. Barrier-free requirements still apply at the entrance level, so plan for them early.
- A trade base that already exists. Every residential framer, plumber and HVAC contractor in Southern Ontario knows how to build this. You’re not limited to commercial contractors with commercial pricing.
- Faster permit review. Part 9 buildings generally have shorter legislated review timelines than large Part 3 buildings.
Slab-on-Grade: The Underrated Cost Saver
Many of these buildings work best without a basement. Slab-on-grade means:
- No deep excavation, shoring or large volumes of soil to haul away
- Less exposure to groundwater, waterproofing failures and sump issues
- No below-grade units with their light, egress and ceiling height challenges
- A faster foundation stage, so framing starts sooner
The trade-off: you give up basement floor area, so mechanical rooms, storage and service space need to be planned above grade. Frost protection and slab insulation need to be detailed properly. For most sites, the savings outweigh what you lose.
Better Parking Layouts
Without a basement or underground garage, surface parking is designed around a simple, efficient building footprint. A compact rectangular building leaves cleaner drive aisles, fewer awkward stalls and better snow storage. Many municipalities have also reduced parking minimums in recent years — always check your specific zoning, because it varies a lot.
How It Stacks Up
| Fourplex | 10-unit, 3-storey (Part 9) | 11+ units or Part 3 | |
|---|---|---|---|
| Site plan approval | No | Generally no (outside shoreline/rail areas) | Yes |
| OBC path | Part 9 | Part 9 | Usually Part 3 |
| Construction | Wood frame | Wood frame, minimal steel | Often steel/concrete, more complex |
| Typical approvals before permit | Zoning, permit | Zoning, permit | Zoning, site plan, permit |
| Consultant team | Small | Moderate | Large |
| Income potential | Limited | Strong | Strong, but slower to reach |
What This Strategy Doesn’t Avoid
We’re big believers in this building type, but we won’t oversell it. You still need to plan for:
- Zoning. Many residential zones don’t permit a 10-unit apartment building as-of-right. A minor variance or zoning by-law amendment may still be needed. Always confirm before you buy.
- Development charges. New units on a new build generally attract development charges. Some municipalities offer reductions, exemptions or deferrals for certain rental housing — check before you finalize your pro forma.
- Civil engineering. Grading, drainage, stormwater and servicing still need to be designed, even without site plan approval.
- Fire department access, barrier-free requirements and exiting. These shape the site layout and the building plan from day one.
- Sprinklers and fire separations. Not always required at this scale, but sometimes worth including for design flexibility. Decide this early.
What Investors Get Wrong
- Buying the land before confirming zoning allows 10 units
- Designing 11 units “because the lot fits it” and triggering site plan approval
- Drawing a 4-storey building and pushing the project into Part 3
- Forgetting the 120 m shoreline / 300 m railway check
- Underestimating servicing upgrades for water and sewer connections
How Rojas Empire of Design Helps
- Feasibility before you buy — zoning, unit count, Part 9 fit, parking and site plan exemption check.
- Design that stays inside the sweet spot — 10 units, 3 storeys, Part 9, efficient footprint.
- Full consultant breakdown — structural, civil, HVAC, energy, survey and geotechnical as needed.
- Permit drawings and examiner coordination through to issued permit.
Final Thoughts
The 10-unit, 3-storey building isn’t a loophole. It’s what the current rules are designed to encourage: more housing, built faster, by smaller builders. If you pick the right lot and design it right, it’s one of the strongest risk-adjusted plays available to Ontario investors right now.
Got a lot in mind? Send us the address. We’ll tell you whether it can support 10 units before you spend a dollar on design.
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