# Multiplex Conversion Toronto | Multiplex Toronto Builders

URL: https://multiplextorontobuilders.ca/multiplex-conversion/

![Toronto semi-detached brick house partway through a multiplex conversion with a new side entrance](/images/misc/toronto-semi-detached-brick-house-mid-conversion-t.webp)

Design \* Build \* Deliver - Multiplex Conversion

# Multiplex Conversion in Toronto, ON | For Homeowners With Existing Houses

Last updated: October 21, 2026

House-to-multiplex conversions of Victorians, bungalows and post-war two-storeys into 2-4 legal self-contained units, with fire separation, utility upgrades and heritage review planned before demolition starts.

Price band (CAD)

$250K-$900K

Timeline

6-9 months construction after permits

Built for

Homeowners With Existing Houses

-   Licensed Ontario Builder
-   Heritage Preservation Services Coordination
-   WSIB Compliant
-   Insured & Bonded
-   15 Years Toronto

## Request Written Feasibility

Zoning check + CAD estimate before any deposit.

Thanks, we got your project details.

We reply within one business day to book your feasibility review.

-   ★5-Star Multiplex Construction Rating
-   ◆15+ Years of Toronto Infill Construction Experience
-   ◆40+ multiplex projects coordinated
-   ◆Free in-home feasibility with written zoning verification

Multiplex Toronto Builders

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 converts existing houses into legal multiplexes across Toronto, East York, Scarborough, Etobicoke, North York and the GTA. We turn Victorians, semis, wartime houses and post-war bungalows into two to four self-contained units, working under HCRA registration, Tarion enrolment where the project qualifies, WSIB and a $5M CGL policy. Every scope is written in CAD and checked against the Ontario Building Code. We coordinate with the Toronto Committee of Adjustment, Toronto Building, Toronto Water, Toronto Hydro, Heritage Preservation Services and your insurer, so the parts of a conversion that usually stall are handled up front.

Conversions fail in predictable ways. Owners are sold a fourplex when the house only has headroom for three, severance gets confused with multiplex approval, EHON setback math is applied to an addition that cannot fit on a 25-foot lot, or a parking variance is promised with no Committee of Adjustment filing behind it. We scope each conversion to OBC Part 9, detail fire and sound separations that pass the first time, spec insulated glazing for new windows, use 316 stainless fasteners near the lake, and verify zoning through GeoWarehouse before you sign anything.

Conversions typically cost **$250K-$900K CAD** and take 6-9 months of construction after permits. We work in Toronto, East York, Scarborough, Etobicoke, North York, York, Vaughan, Markham, Richmond Hill, Mississauga, Brampton and Pickering, and every project carries a written workmanship warranty.

![Interior of a Toronto house mid-conversion with new unit separation wall framing and resilient channel ceiling](/images/content/interior-of-a-toronto-house-mid-conversion-with-ne.webp)

Not sure whether to convert or rebuild? Our guide on 

convert vs rebuild

[/guide/convert-vs-rebuild-multiplex/ →](/guide/convert-vs-rebuild-multiplex/)

 lays out the trade-offs, and 

multiplex construction

[/multiplex-construction/ →](/multiplex-construction/)

 covers full new builds.

## Types of Multiplex Conversion Work

### Basement Underpinning and Bench Footings

The basement is usually the most valuable new unit in a conversion and the hardest to make legal. Many older Toronto basements sit well under the minimum ceiling height for a dwelling unit. Full underpinning lowers the floor by digging under the existing foundation in sequenced sections, then pouring new footings and walls. Bench footings leave a concrete ledge around the perimeter, which costs less and works when the height gap is smaller. Slab lowering alone can work when the footings are already deep. On semis we also need engineering for the party wall and notice to the neighbour. Each method changes cost and schedule, so we choose after a test pit, not before.

### Unit Separation Walls for Fire and Sound

Every unit must be separated from the others with rated assemblies. In practice that means Type X drywall, resilient channel, mineral wool such as Roxul Safe’n’Sound, acoustic sealant at every seam and penetration, and self-closing fire doors at shared stairs. Our target is a 45-minute or 1-hour fire-resistance rating and STC 50+ between units, which blocks normal conversation. Interconnected smoke and CO alarms tie the whole building together. Tenants notice sound long before they notice finishes, so this is where we refuse to cut corners.

### Electrical Service Upgrade and Meter Bank

A house built for one family usually has a service that cannot carry three or four kitchens, laundries and heat pumps. Most conversions need a larger Toronto Hydro service and a meter bank so each unit pays its own electricity, or check meters where separate utility accounts are not practical. We apply at permit stage because the utility side often sets the occupancy date. ESA inspection is booked and passed before drywall closes in.

### Water Service Upgrade (25mm or 38mm Lateral)

Older Toronto homes often have a 12mm or 19mm water line, sometimes still lead or galvanized steel. Four units with four bathrooms and laundries need more flow. Toronto Water frequently requires an upgraded lateral, typically 25mm or 38mm, and we add a backflow preventer and separate shut-offs per unit. The street cut and the city connection need their own permit and scheduling, which we handle.

### Bedroom-Count Feasibility

Rent depends on bedrooms, and bedrooms depend on egress. Each bedroom below the main floor needs a compliant egress window, and every unit needs a safe path out. We test how many bedrooms each unit can legally carry against ceiling height, window size and stair layout. That bedroom count feeds directly into your rental pro forma and your lender’s appraisal.

## Common Multiplex Conversion Problems in Toronto

### Heritage Overlay Blocks Conversion on a Riverdale Victorian

**Symptom:** You own a Riverdale Victorian and your designer’s drawings show new front windows, a widened entrance and a third-floor dormer facing the street. The permit stalls. **Immediate action:** Check whether the house is listed or designated on the Toronto Heritage Register before any exterior design. **Scope:** Heritage Preservation Services must sign off on facade and exterior changes, but interior work into separate units frequently proceeds with fewer limits. **Qualified contractor response:** We keep the street face intact, put new entrances at the side or rear where possible, and use rear additions and interior reconfiguration to create the units. Our Riverdale Victorian triplex kept its original facade and passed HPS review, and the interior now holds three self-contained units. We plan the extra review time into the schedule so it never surprises you mid-project.

### Severance Confused With Multiplex Approval

**Symptom:** You have been told you need to sever your lot before you can add units, or a realtor has suggested severing to sell units separately. **Immediate action:** Separate the two goals before spending money. **Scope:** A multiplex keeps all units on one lot. Severance splits land into separate parcels through a Committee of Adjustment consent process, which is slower, costlier and often impossible on a standard Toronto lot. **Qualified contractor response:** For rental or family use, we design the multiplex on one title. If you want to sell units individually, we explain the condominium route and its costs honestly, and connect you with a real estate lawyer before anyone draws a line on a survey.

### Basement Ceiling Too Low for a Legal Unit

**Symptom:** The basement looks fine, but a tape measure shows well under the minimum ceiling height once ducts and beams are counted. **Immediate action:** Dig a test pit at the foundation wall to see footing depth and soil. **Scope:** Options run from rerouting ducts and slab lowering through bench footings to full underpinning, each with different cost and time. On semis, the shared wall needs engineering and neighbour notice. **Qualified contractor response:** We get an engineer’s recommendation, price the cheapest method that produces a legal unit, and sequence the work before framing. The difference between bench footings and full underpinning can be tens of thousands of dollars, so this decision belongs in the feasibility stage, not halfway through demolition.

### Toronto Hydro Service Upgrade Stalls Occupancy

**Symptom:** The units are finished, the inspections passed, and the tenants are lined up, but the new electrical service is not energized. **Immediate action:** Check the status of the service upgrade application and the meter bank. **Scope:** Utility upgrades follow their own queue. If the application goes in late, the building sits empty while you carry the loan. **Qualified contractor response:** We submit the Toronto Hydro service upgrade and the Toronto Water lateral at permit stage, track both weekly and plan the construction schedule around their dates. On our conversions, utility work is a line item on day one, not a scramble at the end.

Why Owners Pick Us

## Why Choose Multiplex Toronto Builders for Multiplex Conversion?

Six things we do on every project, written into the scope before you sign anything.

### Existing-Condition Survey First

Before we price a conversion we open up what we need to: foundation depth, joist sizes, knob-and-tube wiring, old lead or galvanized water lines. You get a scope based on your actual house, not a guess.

### Fire and Sound Done Once

We detail 45-minute or 1-hour fire separations with Type X drywall, resilient channel, Roxul Safe'n'Sound and acoustic sealant to hit STC 50+, so inspectors pass it and tenants do not hear each other.

### Utility Upgrades Ordered Early

Toronto Hydro service upgrades and meter banks, Toronto Water lateral upsizing and gas separation all have long lead times. We file them at permit stage so occupancy is not held up waiting on a utility truck.

### Heritage Experience

We work with Heritage Preservation Services on listed and designated homes in Riverdale, Leslieville and Cabbagetown, keeping facades intact while the interior becomes legal units.

### Honest Unit Count

Some houses make a great triplex and a poor fourplex. We tell you which, based on ceiling heights, egress, stairs and servicing, before you commit to drawings.

### Fixed Price After Feasibility

After the written feasibility report and existing-condition review, your conversion is priced as a fixed contract with allowances listed separately. No open-ended cost-plus.

Execution Roadmap

## How Does Multiplex Conversion Work With Us?

Four steps from the first zoning check to keys. Typical timeline: 6-9 months construction after permits.

1.  1
    
    ### Step 1: Zoning Check & Existing-Condition Survey
    
    GeoWarehouse zoning pull, heritage screen, structural and services walk-through, and a written feasibility with unit count and CAD budget.
    
2.  2
    
    ### Step 2: Design, Heritage & Permit Drawings
    
    Unit layouts, fire and sound separation details, egress windows and HPS submissions where needed, then a stamped permit set.
    
3.  3
    
    ### Step 3: Permits, Utilities & Pre-Construction
    
    Toronto Building permit, Toronto Hydro service upgrade, Toronto Water lateral and Tarion where the project qualifies as a new home.
    
4.  4
    
    ### Step 4: Conversion Build & Occupancy
    
    Underpinning or bench footings, framing, MEP rough-in per unit, inspections, finishes and occupancy for each unit.
    

Published CAD Pricing

## How Much Does a Multiplex Conversion Cost in Toronto?

Converting an existing Toronto house into a multiplex typically costs **$250K to $900K CAD**, or about **$220-$380 per sqft**. That is lower per square foot than a new build, but the range is wide because every old house hides something different.

The biggest cost drivers we see:

-   **Basement height:** underpinning a full basement adds more than bench footings or slab lowering
-   **Unit count:** two units is a very different job from four
-   **Fire and sound separation:** ceilings and walls between every unit, plus self-closing fire doors
-   **Utilities:** Toronto Hydro service upgrade, meter bank and a 25mm or 38mm Toronto Water lateral
-   **Heritage review:** extra design time and sometimes restricted window or door changes
-   **Finish level:** luxury finishes add $80-$150 per sqft

The written feasibility report gives you a realistic range for your house. After the existing-condition survey, we fix the price.

Try the Multiplex Cost Calculator

[/tools/ →](/tools/)

| Unit Type | Price (CAD) | Project | Timeline |
| --- | --- | --- | --- |
| Triplex New Build | $400K-$1.1M | 3 units, Part 9 | 8-10 months |
| Fourplex New Build | $500K-$1.4M | 4 units, as-of-right citywide | 9-12 months |
| Sixplex (Approved Zones) | $800K-$2M | 6 units, Part 3 likely | 12-16 months |
| House-to-Multiplex Conversion | $250K-$900K | 2-4 units in existing house | 6-9 months |
| Architectural Design (Stamped) | $15K-$60K | Permit drawing set | 6-10 weeks |
| Permit Coordination | $5K-$18K | Toronto Building + CoA | 9-14 weeks |
| Feasibility Assessment | $1,500-$4,500 | Written zoning + budget report | 1-2 weeks |

Per-sqft guide: $220-$380/sqft

Priced per conversion.

Straight Answer

## Isn't It Cheaper to Just Add a Basement Suite?

For one extra unit, yes. A single basement suite is often the cheapest way to add rental income. In our opinion, it also leaves a lot on the table if your house and lot can carry three or four units.

Many of the big costs in a conversion are fixed once you start: the permit, the structural engineer, the hydro service upgrade, the water line, the fire separation on the ground-floor ceiling. Adding a second or third unit while those trades are already on site costs far less than coming back in five years to do it again.

We price both options in the feasibility report. If a basement suite is the right answer for your house, we will say so. If a triplex or fourplex conversion gives you a better return on the same mobilization, you will see the numbers side by side.

Our Work

## Multiplex Conversion Project Photos

Finished exteriors, interiors and site stages from Toronto and GTA projects. Click any photo to enlarge.

 

![](data:image/gif;base64,R0lGODlhAQABAAAAACw=)

Client Feedback

## What Owners Say About Our Multiplex Conversion

> "Converted our Oak Ridges house to two units under Richmond Hill's suite rules. Water and hydro upgrades were scheduled early so occupancy wasn't held up."

Farah M., Oak Ridges Two-unit conversion

> "Our 1920s semi in Roncesvalles needed underpinning, which scared us. They walked us through bench footings versus full underpinning and we saved real money on the front half. Three units now."

Joanna K., Roncesvalles Triplex conversion

> "We stayed in the upper unit while they finished the main and basement units. Dusty for a few weeks, but they kept us in the loop and the separations passed inspection the first time."

Ravi N., Pape Village Three-unit conversion

Guides

## Multiplex Conversion Guides

Plain-language answers to the questions owners ask before they commit. Each guide links back here when you are ready for numbers.

Can a Heritage Home Become a Multiplex in Toronto?Explainer

[/guide/heritage-home-multiplex-conversion/ →](/guide/heritage-home-multiplex-conversion/)

Convert or Rebuild? House Conversion vs New Multiplex BuildDecision guide

[/guide/convert-vs-rebuild-multiplex/ →](/guide/convert-vs-rebuild-multiplex/)

Do You Need to Underpin the Basement for a Multiplex Conversion?Explainer

[/guide/underpinning-basement-multiplex-conversion/ →](/guide/underpinning-basement-multiplex-conversion/)

Fire Separation and Soundproofing Between Units in a Converted HouseExplainer

[/guide/fire-separation-soundproofing-between-units/ →](/guide/fire-separation-soundproofing-between-units/)

How to Convert a House into a Multiplex in TorontoExplainer

[/guide/how-to-convert-a-house-into-a-multiplex/ →](/guide/how-to-convert-a-house-into-a-multiplex/)

Hydro, Water and Meter Upgrades That Stall Multiplex ConversionsExplainer

[/guide/multiplex-conversion-utility-upgrades/ →](/guide/multiplex-conversion-utility-upgrades/)

Browse all multiplex guides

[/guide/ →](/guide/)

Toronto Zoning FAQs

## Multiplex Conversion FAQs

### How much does it cost to convert a house into a multiplex in Toronto?

Most conversions land between $250K and $900K CAD, or about $220-$380 per sqft. Basement underpinning, the number of units, fire separation work and utility upgrades are the main drivers. The fixed price follows a written feasibility and existing-condition survey.

### Do I need to sever my lot to convert to a multiplex?

No. A multiplex keeps every unit on one lot and one title. Severance divides land into separate parcels and is a different Committee of Adjustment process. Under EHON you can have up to four units on a Toronto lot without severing it.

### Can a heritage home become a multiplex?

Often, yes. Listed and designated homes need Heritage Preservation Services sign-off for facade and exterior changes, but interior reconfiguration into units frequently proceeds. Expect extra review time in Riverdale, Leslieville and Cabbagetown.

### Do I need to underpin my basement?

Only if the basement cannot reach the minimum ceiling height for a dwelling unit any other way. Bench footings or slab lowering can work when the gap is small. Full underpinning costs more and adds weeks, but it often creates the most valuable unit in the house.

### What fire separation is required between units?

Typically a 45-minute or 1-hour fire-resistance rating between units, depending on the building and whether it is sprinklered. That usually means Type X drywall, mineral wool, sealed penetrations, self-closing fire doors and interconnected smoke and CO alarms across all units.

### Will I need a Toronto Hydro service upgrade?

Most conversions to three or four units need a larger electrical service and a meter bank so each unit is metered separately. We apply at permit stage because Toronto Hydro lead times can run several months.

### Do I need a bigger water line for a multiplex?

Often. Many older Toronto houses have a small or lead service line. Toronto Water frequently requires an upgrade to 25mm or 38mm for three or four units, plus a backflow preventer. We check the existing line during feasibility.

### Can I live in the house during the conversion?

Sometimes, if the work is phased and one unit stays separated and safe. It adds time and cost, and some stages such as underpinning or service upgrades may require short moves. We plan it with you at the design stage.

### How many units can my house become?

Up to four as-of-right in the City of Toronto, subject to ceiling heights, egress, stairs, parking rules and servicing. Many houses make an excellent triplex. Outside Toronto, the local additional residential unit rules apply instead of EHON.

### Is converting cheaper than building new?

Per square foot, usually yes: $220-$380 for conversion against $320-$520 for new construction. But a poor foundation, low basement or awkward layout can flip that math. We compare both in the feasibility report.

### How long does a multiplex conversion take?

Plan on 6-9 months of construction after permits, plus 1-2 weeks for feasibility, 6-10 weeks for design and 9-14 weeks for permit coordination. Heritage review or a variance adds time.

### Do you do conversions in East York and York?

Yes. Wartime and post-war houses in East York and older semis in York are some of our most common conversions. We also convert homes across Toronto and in GTA cities under their own suite rules.

Related Services

## Related Multiplex Services

### Multiplex Construction

Ground-up triplex, fourplex and approved-zone sixplex builds on Toronto infill lots, scoped to OBC Part 9 or Part 3 by unit count and height.

$400K-$2M

View multiplex construction

[Multiplex Construction →](/multiplex-construction/)

### Multiplex Additions

Rear, side and storey additions that create or enlarge units, with structural tie-in and a foundation check before design.

$180K-$600K

View multiplex additions

[Multiplex Additions →](/multiplex-additions/)

### Building Permits

Zoning certificates, permit applications, CoA minor variances with hearing representation, utility and right-of-way permits, and inspections.

$5,000-$18K

View building permits

[Building Permits →](/multiplex-building-permits/)

### Feasibility Assessment

Written report in 1-2 weeks: GeoWarehouse zoning pull, unit-count test, servicing check, heritage and tree screen and a CAD budget range.

$1,500-$4,500

View feasibility assessment

[Feasibility Assessment →](/multiplex-feasibility-assessment/)

![](/images/misc/finished-brick-and-oak-toronto-multiplex-exterior-.webp)

Start With Certainty

## Get a Fixed Number for Your Multiplex Conversion

Send us your address and we come back with a zoning read, an honest unit count and a CAD budget range in writing, before you spend on drawings.

Get a Written Feasibility Assessment

[/contact/ →](/contact/)

 

See All Services

[/services/ →](/services/)

-   Written zoning verification
-   CAD price bands before deposit
-   Licensed Ontario Builder, Insured & Bonded