# Multiplex Construction Markham | Multiplex Toronto Builders

URL: https://multiplextorontobuilders.ca/service-areas/markham/

![Unionville heritage-style home with a discreet rear addition](/images/misc/unionville-heritage-style-home-with-a-discreet-rea.webp)

Outside Toronto - Local Zoning

# Multiplex Construction in Markham, ON for Multigenerational Families

Last updated: October 21, 2026

Additional units, multigenerational layouts and heritage-sensitive additions in Unionville, Markham Village, Cornell and Berczy Village, under the city's own additional residential unit rules.

Zoning

Local rules (not EHON)

Unit limit

Local additional residential unit rules (not EHON)

Response

Written feasibility in 1-2 weeks

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## Request a Written Feasibility Report

Zoning check + CAD estimate before any deposit.

Thanks, we got your project details.

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

Local Overview

## Family Suites From Unionville to Cornell

Multiplex Toronto Builders

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 helps Markham families add legal units in Unionville, Markham Village, Thornhill, Milliken Mills, Cornell, Berczy Village, Cathedraltown and Cachet. The city runs its own additional residential unit by-law, and Toronto's EHON rules do not apply here. Projects go through the local Committee of Adjustment, local building services and York Region servicing, and in Unionville and Markham Village, heritage conservation district rules often shape exterior work.

Multigenerational living is the main driver of our local work. Families want grandparents close, adult children nearby and sometimes a rental to help with costs. Many homes here are large two-storey houses with deep basements and wide lots, which make legal basement units and 

rear additions

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

 practical.

Additions typically run $180K-$600K and 

conversions

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

 $250K-$900K depending on scope. One Unionville client started with a $3,200 

feasibility report

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

 that confirmed a main house plus an additional unit for grandparents, with a budget range they could take to the bank.

Zoning framework: **Markham additional residential unit (ARU) by-law**. Sixplex status: No. Toronto EHON does not apply here.

Avoid Costly Mistakes

## Markham Additional Unit Problems We Solve

The local issue that catches owners out most often, then the four problems we see on most lots here, and how we handle each before you spend on design.

The Local Issue

### A Parent Suite Behind a Unionville Heritage Streetscape

What you see

You want to add a suite for parents to a house on or near Main Street Unionville, and the addition has to look like it belongs.

Why it happens here

Unionville has been a heritage conservation district since 1998, so every exterior change needs a Markham heritage permit. After the mayor vetoed the four-unit decision, extra units still rely on the existing ARU rules.

What we do

Our architectural design team draws a rear addition that follows the district guidelines and files the heritage permit before the building permit.

### Assuming Toronto EHON Rules Apply

The city is outside Toronto, so EHON's fourplex and sixplex permissions do not apply. The city's own ARU by-law sets the unit count.

Our fix: We design to the city's additional residential unit rules, confirmed for your property during feasibility.

### Heritage District Rules in Unionville and Markham Village

Heritage conservation districts limit exterior changes, additions and materials on many older streets.

Our fix: We design additions and entrances to meet district guidelines and prepare heritage submissions early.

### Additional Unit Count Limits

The city's rules cap the number of additional units and set size and entrance requirements.

Our fix: We plan the best layout inside the current limits rather than designing for rules that do not apply.

### Parking on Suburban Streets

Additional units can bring parking requirements that are hard to meet on some suburban lots.

Our fix: We check the parking standard during feasibility and design driveways and entrances to meet it.

Services

## Additions, Suites and Multigenerational Layouts

Every service we offer is available here, with the ones local owners need most listed first. Where local rules differ from Toronto's EHON, we design to the local by-law.

### 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/)

### Architectural Design

Concept, zoning review, BCIN or OAA stamped permit drawings, structural and MEP coordination and SB-12 energy compliance.

$15K-$60K

View architectural design

[Architectural Design →](/multiplex-architectural-design/)

### Multiplex Conversion

Existing Victorians, semis and bungalows reworked into 2-4 legal self-contained units, with underpinning, fire separation and separate meters planned up front.

$250K-$900K

View multiplex conversion

[Multiplex Conversion →](/multiplex-conversion/)

### 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/)

### Fourplex Construction

Four-unit new builds, as-of-right citywide under EHON, on standard, corner and narrow Toronto lots with separate hydro and HRV per unit.

$500K-$1.4M

View fourplex construction

[Fourplex Construction →](/fourplex-construction/)

### Triplex Construction

Three-unit new builds for narrow lots and multigenerational families: basement, main and upper units with separate entrances and fewer variances.

$400K-$1.1M

View triplex construction

[Triplex Construction →](/triplex-construction/)

### Sixplex Construction

Six-unit builds only in the 2025 approved zones: Toronto and East York District and Scarborough Ward 23 North, with Part 3 scope priced up front.

$800K-$2M

View sixplex construction

[Sixplex Construction →](/sixplex-construction/)

### Design-Build

Feasibility, stamped design, permits and construction under one contract and one PM, priced as it is drawn and fixed after feasibility.

$50K-$150K

View design-build

[Design-Build →](/multiplex-design-build/)

### 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/)

Published CAD Pricing

## How Much Does a Multiplex Cost in Markham?

Published price bands for the work we do most here. Unit counts follow local rules, not Toronto EHON.

| Unit Type | Price (CAD) | Project | Timeline |
| --- | --- | --- | --- |
| House Conversion (2+ units) | $250K-$900K | Units under local rules | 6-9 months |
| Rear Addition | $180K-$400K | New or enlarged unit | 5-8 months |
| Side Addition | $220K-$600K | New or enlarged unit | 5-8 months |
| Triplex New Build (where permitted) | $400K-$1.1M | Subject to local by-law | 8-10 months |
| Architectural Design (Stamped) | $15K-$60K | Permit drawing set | 6-10 weeks |
| Permit Coordination | $5K-$18K | Local building dept. + CoA | 9-14 weeks |
| Feasibility Assessment | $1,500-$4,500 | Written zoning + budget report | 1-2 weeks |

Fixed pricing is issued after a written feasibility report. Luxury finishes add $80-$150 per sqft.

Execution Roadmap

## Our Heritage-Aware 4-Step Process

1.  1
    
    ### Step 1: Zoning Verification & Feasibility
    
    GeoWarehouse parcel pull, zoning permissions, setback and coverage math, servicing screen and a written CAD budget range in 1-2 weeks.
    
2.  2
    
    ### Step 2: Architectural Design & CoA Coordination
    
    BCIN or OAA stamped drawings that make the most of rentable area, energy compliance, and a Committee of Adjustment filing only if it pays off.
    
3.  3
    
    ### Step 3: Permit Approvals & Pre-Construction
    
    Building permit, water and hydro applications filed in parallel, and Tarion enrolment for new homes before we break ground.
    
4.  4
    
    ### Step 4: Construction Delivery & Occupancy
    
    Fixed-price construction, inspections booked and passed, separate systems per unit and a first-visit occupancy pass.
    

## Ready to Plan a Suite for Family?

Zoning check, honest unit count and a CAD budget range in 1-2 weeks, before any deposit. No obligation to build with us.

Get a Written Feasibility Assessment

[#location-form →](#location-form)

What We Build Here

## What Sets Our Work in Heritage Districts Apart

### Multigenerational Layouts

Accessible suites for grandparents, separate units for adult children and shared outdoor space, all as legal self-contained units.

### Heritage-Sensitive Additions

Rear additions and new entrances in Unionville and Markham Village designed to fit heritage conservation district guidelines.

### Legal Basement Units

Deep local basements turned into bright legal units with egress, fire separation and separate entrances.

### Local ARU Compliance

Design and permits under the city's additional residential unit by-law with York Region servicing.

Lot Types

## The Four Lot Types We See Most

What each lot type usually supports, so you can place your own property before the feasibility visit.

1.  1
    
    ### 50-Foot Suburban Lot
    
    Room for a basement unit and a rear addition. Common across Milliken Mills and Berczy Village.
    
2.  2
    
    ### Heritage District Lot
    
    Unionville and Markham Village lots where exterior work follows district guidelines.
    
3.  3
    
    ### Newer Subdivision Lot
    
    Cornell and Cathedraltown homes, often with lanes and garages that change the options.
    
4.  4
    
    ### Corner Lot
    
    Two frontages for separate entrances, with sight triangle limits.
    

Client Feedback

## What Local Owners Say

> "Markham Village house in the heritage district. Rear addition for my parents that you can barely see from the street, and the district review went smoothly."

Jennifer Y., Markham Village

> "Basement suite with its own entrance for our son. They knew the local rules cold and the permit came through on the first submission."

Raj B., Milliken Mills

> "Cornell home with a lane garage. They showed us how the garage area could fit into the plan for an extra unit under the city's rules. Clear and honest."

Stephanie L., Cornell

Before You Design

## Planning a Family Suite Near Heritage Streets: What to Check First

Local projects start with the local additional residential unit by-law, not Toronto's EHON. The by-law sets how many additional units are allowed, their size and how they are accessed. Confirming what applies to your property is the first step.

Second, check heritage status. Unionville and Markham Village have heritage conservation districts where additions, entrances and exterior materials are reviewed. Projects here work best when the new space sits at the rear and the street face stays as it is.

Third, decide on the unit type. Many local families want a suite for grandparents, which points toward an accessible ground-floor unit or a rear addition with a level entry. Others want a basement unit for an adult child or a tenant. Each has a different cost and timeline.

Fourth, consider newer neighbourhoods carefully. Cornell, Cathedraltown and other newer areas often have rear lanes and garages, which can open different options than older streets with front driveways.

Finally, check servicing and parking. Water and sewer run through the city and York Region, and parking rules can affect where the new entrance and driveway go. A written feasibility report covers these alongside the by-law check.

Local Knowledge

## Why Heritage Districts and ARU Rules Shape the Plan

Local projects follow the **Markham ARU by-law**, not Toronto's EHON. On older streets, the **Unionville heritage conservation district** and Markham Village district add design review for anything visible from the street.

Variances go to the **local Committee of Adjustment**. Servicing runs through **York Region**, and the **Stouffville GO line** gives some neighbourhoods good transit access, though most projects still plan for driveway parking.

### The Housing Stock We Work With

The city is mostly **1980s to 2010s detached homes** with deep basements, plus historic homes in Unionville and Markham Village and newer lane-access homes in Cornell. Multigenerational households are common, so accessible design comes up often.

![Accessible ground-floor suite entrance on a Markham home](/images/misc/accessible-ground-floor-suite-entrance-with-level-.webp)

Accessible ground-floor suite entrance on a Markham home

Coverage

## Neighbourhoods We Cover in Markham

-   Unionville
-   Markham Village
-   Thornhill (Markham)
-   Milliken Mills
-   Cornell
-   Berczy Village
-   Cathedraltown
-   Cachet

Postal codes (FSAs) we cover: L3P, L3R, L3S, L6B, L6C, L6E, L6G

Local Landmarks

## Landmarks and Transit Near Our Projects

-   Main Street Unionville
-   Markham Civic Centre
-   Markville Shopping Centre
-   Rouge National Urban Park
-   Pacific Mall

Served by Highways 404 and 407, with Stouffville line GO stations at Unionville, Centennial, Markham and Mount Joy, and Viva buses on Highway 7.

### Nearby Service Areas

Multiplex construction in Scarborough

[/service-areas/scarborough/ →](/service-areas/scarborough/)

Multiplex construction in Richmond Hill

[/service-areas/richmond-hill/ →](/service-areas/richmond-hill/)

Multiplex construction in Pickering

[/service-areas/pickering/ →](/service-areas/pickering/)

Local Questions

## Markham Suite and Addition FAQs

### Does EHON apply in Markham?

No. The city uses its own additional residential unit by-law. Fourplex and sixplex permissions under Toronto's EHON do not apply.

### How many units can I add?

It depends on the current ARU provisions and your property. Markham's mayor vetoed a council decision to allow up to four units on certain lots, so the existing rules still apply. We confirm what is allowed during feasibility.

### Can I build an addition in the Unionville heritage district?

Often, yes, if it follows the district guidelines. Rear additions that stay out of view from the street usually work best.

### What does a multigenerational project cost?

Additions typically run $180K-$600K CAD and conversions $250K-$900K, depending on scope and accessibility features.

### Who handles servicing?

The city and York Region. We check capacity and connection costs during feasibility.

### Will a Unionville addition need a variance as well as a heritage permit?

You may need one if an addition or new entrance does not meet setback, coverage or height rules, or if parking cannot be provided. We test the design against the by-law first and design to avoid variances where we can.

### Also Serving 20 Near-GTA Municipalities

Outside our 12 core areas we take on feasibility, design and build work in these municipalities. Each runs its own zoning and additional unit rules, and Toronto EHON does not apply in any of them.

-   Oakville
-   Burlington
-   Milton
-   Halton Hills
-   Caledon
-   King Township
-   Aurora
-   Newmarket
-   Whitchurch-Stouffville
-   East Gwillimbury
-   Georgina
-   Uxbridge
-   Ajax
-   Whitby
-   Oshawa
-   Clarington
-   Scugog
-   Bradford West Gwillimbury
-   New Tecumseth
-   Hamilton

![](/images/misc/warm-morning-view-of-a-finished-brick-and-oak-mult.webp)

Start With Certainty

## Book a Markham Feasibility Review

Send the address and we will confirm the zoning, the realistic unit count and a CAD budget range for your property in writing.

Get a Written Feasibility Assessment

[/contact/ →](/contact/)

 

All Service Areas

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-   CAD price bands before deposit
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