GTA · Mississauga · Oakville · Burlington · Milton · Hamilton · Toronto
Legal Basement Apartments, Garden Suites & Garage Conversions
Explore a legal additional unit with one GTA construction team. HMH assesses your basement, lot or garage, manages the design and permit process, and builds to the approved plan.
Google 4.9★
164 reviews · 2 locations
HomeStars 5.0★
Consistently, year over year
WSIB + Fully Insured
Your home is protected
25+ Years
Experience in the GTA
Permits Handled
Start to final inspection
Build the Right Type of Additional Unit
Legal Basement Apartments
Convert an existing basement into a legal second unit with the right layout, fire separation, egress, permits and inspections.
Garden Suites & ADUs
Plan a detached additional unit for your property with a clear feasibility, design, permit and construction path.
Garage Conversions
Assess whether your garage can become a legal, functional living space and understand the project steps before you commit.
Every property and municipality is different. Your assessment starts with your project goals, site conditions and the local approval path — then HMH can recommend the next practical step.
From Single-Family to Legal Multi-Unit in 3 Steps
- 1
Feasibility & Design
We assess your basement, lot, or garage against your city's zoning and Ontario Building Code second-unit rules — ceiling heights, egress, fire separation, parking — then design a unit that qualifies.
- 2
Permits & Approvals
Drawings, permit applications, and municipal registration of the second unit are handled for you. No guessing which rules apply in Mississauga versus Toronto versus Hamilton — that's our job.
- 3
Build, Inspect & Legalize
Our crews build to the approved drawings: fire-rated separations, interconnected smoke alarms, egress windows, kitchen and bath, separate entrance if needed. Every stage is inspected, so your unit is legal on paper — not just finished.
Why GTA Homeowners Are Converting Now
Provincial rules changed in homeowners' favour: most residential lots in Ontario can now legally hold additional residential units.
Rental Income
A legal one-bedroom basement suite in the west GTA typically rents for $1,800–$2,500+ per month — income that offsets your mortgage from day one.
Multi-Generational Living
A self-contained suite keeps aging parents or adult kids close with their own kitchen, bath, and front door — without anyone giving up privacy.
Legal Peace of Mind
Illegal suites risk fines, insurance denial, and forced tenant eviction. A registered, inspected unit protects your investment and rents for more.
Conversions, Before & After
Drag the slider. Real project photos coming — placeholders shown.
Before
After
Before
AfterSee HMH Multi-Unit Project Stories
Projects We've Built
Hamilton
Quadplex Conversion in Hamilton
One single-detached house turned into four self-contained legal units — basement, main floor, second floor, and a studio in the detached garage.
Read the story →Hamilton
Triplex Conversion in Hamilton: One House, Three Legal Units
One house, three legal self-contained units — a full triplex conversion in Hamilton, taken from permit drawings through fire separation to occupancy.
Read the story →Hamilton
Duplex Conversion in Hamilton: Adding a Legal Second Unit
A Hamilton house split into two self-contained dwelling units inside its existing footprint: two kitchens, three washrooms, four walls removed, full fire separation and a new code-sized basement egress window.
Read the story →Recent HMH Projects
Real photos from completed HMH Construction jobs across the GTA.
Ontario Second-Unit Rules, Explained
How many units does Ontario allow on my lot?
Under Ontario's current planning rules, most urban residential lots may add additional residential units — commonly a basement or in-house suite plus a detached garden suite — on top of the main home, without a rezoning application. Exact allowances vary by municipality, and we confirm yours as the first step of every project.
What makes a basement apartment legal?
The big ones: adequate ceiling height, proper egress (a way out in a fire, usually a large window or separate entrance), fire-rated separation between units, interconnected smoke and CO alarms, and a building permit with inspections. Many 'finished basements' fail several of these — we build to pass all of them, then register the unit with your city.
Do I need a separate entrance for a basement apartment?
In practice, yes — a private entrance is how a basement suite meets egress rules and how tenants come and go. Separate entrances are our flagship service: we cut and build them in 3 days as part of a conversion.
What is a garden suite, and can I build one?
A garden suite is a detached, self-contained home in your backyard (a laneway house is the laneway version). Toronto, Mississauga, Hamilton, and most GTA municipalities now permit them on qualifying lots, subject to lot size, setbacks, and servicing. We run the feasibility check before you spend a dollar on design.
How long does a conversion take?
A typical basement conversion runs 8–12 weeks of construction after permits, depending on scope. Garden suites take longer because of servicing and foundations. You get a real schedule with your fixed-price quote after a site visit.
What GTA Homeowners Say
Google 4.9★ (164 reviews across our Milton & Mississauga locations) · Consistently 5.0★ on HomeStars
“I recently hired Omar and team to renovate our inlaws basement apartment. His company was so professional and efficient and his attention to detail was amazing. We will be using HMH Construction for all future projects.”
“Omar and his team at HMH constructed one of the first Garden Suites for us… They even handled the design and permitting process for us. They really made everything smooth for us…”
“They built everything from scratch in a highly skilled and timely manner. Even the city inspectors were impressed and passed their work on the first try.”
Request Your Free ADU Feasibility Assessment
Tell us what you are considering and where the property is located. A project lead will review the details and follow up about the next step.
Tell us about your project — we reply within one business day. Or call905-749-4608.
Prefer to talk it through?Call 905-749-4608— we pick up.