Build Three Legal Units With One Design-Build Team

Triplex Construction in Mississauga

At GrandBuild Homes, we design and build triplexes in Mississauga and across the GTA. Whether you are converting an existing home or building a purpose-built triplex from the ground up, our team handles the design, approvals, and construction from start to finish, under one contract.

Understand What Your Property Can Actually Support

A successful triplex construction project starts with understanding the property, not designing the floor plan first. Before starting the design, we assess the property conditions that could affect the project’s scope, requirements, and overall budget.

Existing condition: We review the basement, foundation, floor layout, entrances, and structural system.
Building systems: We assess plumbing, electrical, and HVAC requirements for three units.
Site considerations: For new construction, we review the lot, building size, servicing, access, and unit configuration.
Project feasibility: If you're considering a property for triplex development, assessing these factors before purchase helps you understand the project's scope, requirements, and potential costs.

What a Legal Triplex Actually Requires

A legal triplex is more than a house with three kitchens. The building and each unit must meet applicable zoning, building, and life-safety requirements.
Key considerations include

Fire separation and sound separation
Compliant entrances and egress
Required ceiling heights and window conditions
Plumbing, electrical, heating, and ventilation
Structural requirements
Approved permit drawings

The Ontario Building Code (OBC) influences these requirements from the beginning. For existing homes, parts of the structure may need to be opened up to confirm existing conditions before construction proceeds.

We coordinate required permit drawings (BCIN) and applicable submissions, including the ePLANS portal where required.

Does Your Property Qualify for a Three-Unit Conversion?

Mississauga properties may accommodate three residential units under current provincial and municipal rules, depending on the property and proposed configuration. Ontario’s Bill 23 allows qualifying properties to add two additional units to a primary residence without rezoning.

However, zoning and building requirements for setbacks, height, lot coverage, parking, access, servicing, and other standards still apply. If the proposed triplex building does not meet a specific requirement, a minor variance through the Committee of Adjustment may be needed. We identify these requirements early to help determine whether your project is feasible.

GrandBuild Handles Your Triplex, From Permit to Construction

A triplex involves more moving parts than a typical renovation. Keeping design, approvals, and construction connected helps prevent gaps between different contractors and consultants. Our process includes

Property Assessment

Review the site, existing conditions, and proposed unit configuration.

Design & Permit Drawings

Develop the layout and required BCIN permit drawings.

Building Permit & ePLANS Submission

Submit the building permit application through the ePLANS portal.

Design-Build Construction

Complete the approved structural, mechanical, and finishing work.

Inspections & Completion

Coordinate the required inspections and complete the approved scope.

You have one team responsible for keeping the project moving from the initial assessment through construction.

Conversion or Build New — Which Fits Your Property?

The right approach depends on what the existing property can support.

Converting an Existing House

A house-to-triplex conversion can be practical when the existing structure and layout can be adapted efficiently. The work may include reconfiguring floors, creating separate entrances, upgrading plumbing and electrical systems, improving fire and sound separation, and modifying HVAC and ventilation. Where basement height is limited, underpinning or basement lowering may also be considered where appropriate.

Building a New Triplex

A purpose-built triplex allows the property to be designed around three legal units from the outset. Entrances, structure, building services, parking, fire separation, and unit layouts can all be coordinated before construction begins. This approach provides greater design flexibility when an existing house cannot accommodate the desired three-unit configuration efficiently.

What Triplex Construction Actually Costs

Pricing depends on whether you're converting an existing house or building new, and on the property itself. A conversion is priced around how much of the existing structure can be reused; new construction is priced on size, site conditions, materials, and finishes.

Either way, cost is driven by triplex-specific factors: three kitchens and bathrooms, separate mechanical and electrical systems, fire and sound separation, three entrances, and any structural work the layout requires.

We look at the property first, then price the project based on what it actually needs.

Why Choose GrandBuild for Your Triplex?

Whether you're converting an existing home or building a new triplex, GrandBuild manages the project through one design-build team.

Since 1995 — 30+ years of residential construction experience
100+ homes completed across the GTA
HCRA licensed
Tarion registered, on projects where that applies
One team, one contract — design, permits, and construction, not separate contractors

Triplex Builder Serving Mississauga and the GTA

We build and convert triplexes across Mississauga and the surrounding GTA, including:

Mississauga

Toronto

Oakville

Vaughan

Brampton

Caledon

Richmond Hill

Markham

King City

Every municipality applies its own zoning rules on top of the provincial baseline, so we confirm what's actually permitted on your property before design begins, whether that's a triplex conversion in Mississauga or new construction elsewhere in the GTA.

Triplex Construction FAQs

Can I convert my house into a triplex?

Potentially. The property must be assessed for zoning, layout, structure, access, parking, servicing, and building requirements. Some homes may also need structural or mechanical upgrades.

Can I build three units on my property in Mississauga?

Some properties can accommodate three units under current rules, subject to zoning, building requirements, parking, access, and other conditions. A property-specific assessment is required.

How much does triplex construction cost?

Costs depend on the property and project scope. Conversions may involve structural work, basement upgrades, kitchens, bathrooms, entrances, and mechanical systems. New builds depend on size, design, materials, and site conditions.

Do I need a permit to create a triplex?

Yes. Creating additional residential units and completing construction work requires the appropriate permits and approvals. Requirements vary by project.

Is it better to convert a house or build a new triplex?

It depends on the property. Conversion may work well when the existing layout is suitable, while new construction can offer more flexibility when significant limitations exist.

Can a basement be used as one of the three units?

Potentially. The basement must meet applicable requirements for ceiling height, egress, entrances, fire and sound separation, ventilation, and other building systems.

How long does a triplex conversion take?

Timelines vary based on the property, approvals, design, construction scope, and structural work. A project assessment provides a more accurate schedule.

Can GrandBuild handle both design and construction?

Yes. Our design-build approach combines design, permit coordination, and construction under one team, simplifying the process for homeowners.

How do I find a triplex builder near me?

Start with the property address and your proposed project. The property’s condition and location help determine the right construction approach.

Can you help with a triplex conversion near me?

Yes. We can review the existing property, discuss your proposed three-unit layout, and help determine the appropriate conversion approach.

Ready to See What Your Property Can Support?

Whether you’re planning a triplex conversion or building a new three-unit home, it starts with understanding what the property can support. We’ll assess the configuration, define the work, and help you determine the right path forward.