Converting a Garage Into a Living Space in Ontario: What to Do About the Garage Door

Introduction

Converting a garage into a living space is one of the most popular renovations in southern Ontario right now, and it is easy to see why. A double garage is often the single largest uninterrupted room in the house. Finishing it gives you a home office, a gym, a rental suite, a family room, or a main-floor bedroom for aging parents, all without the cost and disruption of a full addition. In a London market where floor space is expensive and lot lines are tight, the garage is a tempting place to find another two or three hundred square feet.

Most homeowners plan the fun parts first: the flooring, the paint, the furniture. The part that quietly decides whether the project succeeds is the one most people put off, namely the garage door opening. That big rectangle of thin, uninsulated steel is the reason the room is cold in January, the reason it is damp in July, and the single biggest clue to a future buyer that this was a garage. This guide walks through the garage door decision from every angle: whether you even need a permit, the four things you can do with the door opening, how to solve the cold-floor and moisture problems that sink most conversions, the heating and safety issues unique to an attached garage, and the reversibility question that protects your resale value. Every external link here has been checked against a live government or industry page before publication.

Why Homeowners Convert a Garage

Before the door decision, it helps to be honest about the goal, because the goal changes the right answer. The most common conversions we see around London fall into a few buckets. A work-from-home household wants a quiet, separate office that is not the corner of a bedroom. A growing family wants a playroom or a teen hangout that keeps the noise out of the main living area. An aging-in-place family wants a main-floor bedroom and bathroom so a parent does not have to climb stairs. And increasingly, homeowners want a secondary suite for a rental income or for an adult child, which is a much bigger project with its own code requirements.

Each of these has a different tolerance for cost, for permanence, and for whether the space needs to look and feel like a real room or simply be usable. A heated hobby space can keep the garage door in place. A legal bedroom cannot. Knowing which one you are building tells you how far you have to go with the opening.

First Question: Do You Need a Permit?

Yes, almost always. Converting a garage to habitable space is a change of use in the eyes of the Ontario Building Code, and a change of use is exactly the kind of work a building permit exists to control. The Government of Ontario's plain-language guide is explicit that you must obtain a building permit before you "change the use of a building," and it notes that a change-of-use permit can be required "even if you're not planning any construction," because different uses carry different Building Code requirements. You can read the province's overview on the Ontario building permits page.

Locally, the process runs through the city. The City of London building permits department reviews applications to confirm the work meets the Building Code and the local zoning bylaw before any construction starts. That zoning check matters more than people expect on a garage conversion, because your zoning may require a certain number of covered or off-street parking spaces per dwelling. Turning the garage into a bedroom can put you offside on parking even when the construction itself is straightforward, and that is a question to settle at the counter before you buy flooring.

The stakes for skipping the permit are not trivial. Under the Building Code Act, building without a required permit can carry a fine of up to $50,000 for a first offence for an individual. Beyond the fine, unpermitted living space can stall a future sale, void parts of your home insurance after a claim, and force you to open finished walls for an inspector later. Our own guide to garage door permits in Ontario covers the permit question specifically for door work; a full habitable conversion is a larger application, but the principle is the same. When in doubt, phone the building department first. The call is free and the advice is authoritative.

The Garage Door Itself: Your Four Options

Once the paperwork path is clear, the opening itself is the defining decision. There are four realistic things you can do with it, in rough order of cost and permanence.

Option 1: Leave the door in place and insulate behind it

The lowest-cost path keeps the existing garage door and builds an insulated stud wall on the inside of the opening, hidden from the street. The door still looks like a garage door from the curb, but behind it sits a framed, insulated, drywalled wall. This is the choice for a heated hobby room, a gym, or a workshop where you do not need the space to read as a true room and you want to keep the option of reverting later.

The catch is that a standard sectional door is a poor thermal barrier, so the insulation has to do all the work. Even a well-built stud wall behind the door will fight condensation in the cavity between the cold door and the warm wall, which is why this option lives or dies on vapour control and ventilation. If you go this route, disconnect and secure the opener so no one can accidentally drive the door into your new wall, and keep the springs and cables maintained even though the door is no longer in daily use.

Option 2: Remove the door and build an insulated exterior wall

The most common conversion for a true living space removes the door, tracks, springs, and opener entirely, then frames a proper insulated exterior wall in the opening, usually with one or two windows to bring in light and meet egress. Done well, from the street the house no longer looks like it ever had a garage there. This is the right answer for a bedroom, an office, or a family room that needs to feel like part of the house.

This is real construction: a new header may be needed, the wall must be insulated to the same standard as the rest of the house, the exterior finish has to match the existing brick or siding, and the floor almost always needs to be raised and insulated (more on that below). It is also the least reversible option, which is exactly why the reversibility conversation later in this article matters.

Option 3: Swap the door for a full-view glass wall or patio doors

A middle path that is growing in popularity: replace the sectional door with a large fixed window wall, a set of sliding patio doors, or a modern full-view aluminum-and-glass door that can still open. This keeps the light and the indoor-outdoor feel of the wide opening while giving you a weather-tight, insulated barrier. It is a natural fit for a garage that becomes a sunroom, a studio, or a three-season entertaining space. Our guide to full-view aluminum and glass garage doors covers this style, which lets you keep the door as an operable feature while dramatically upgrading the look.

Option 4: Frame the opening down to a standard man-door

Sometimes the best answer is to close most of the opening into an insulated wall but leave a standard exterior man-door for direct access to the yard or driveway. This keeps a functional entrance to the new room, which is handy for a home office with clients or a suite with its own door, without leaving a garage-sized hole in the building envelope.

The Two Problems That Sink Most Conversions

Cosmetics are easy. The two things that turn a converted garage from a proud renovation into a cold, musty regret are temperature and moisture, and both trace back to how a garage was originally built.

The cold, uninsulated slab

A garage floor is a concrete slab poured directly on grade, usually with little or no insulation beneath it and often sloped toward the door for drainage. Left as-is, it stays cold year-round and radiates that cold into the room no matter how good your heating is. The standard fix is to build up the floor: a moisture barrier, rigid foam insulation, a sleeper or subfloor system, and then your finished flooring on top. That build-up also lets you level out the drainage slope. Raising the floor has a knock-on effect on ceiling height and on how the new floor meets the rest of the house, so it needs to be planned, not improvised.

The walls and ceiling matter just as much. Garage walls are frequently uninsulated or only partly insulated, and the ceiling may be open to an unheated attic. To feel like living space and to pass a change-of-use review, all of it typically has to be brought up to the insulation standard of the rest of the home. If you are weighing insulation choices, our explainer on what R-value actually means is a useful primer, and the industry group DASMA publishes homeowner-facing technical data sheets on how door and wall assemblies are rated for thermal performance if you want to go deeper.

Condensation and trapped moisture

The second silent killer is moisture. Garages were designed to breathe; living spaces are sealed. When you seal up a space that used to be vented and then add people, showers, or a kitchenette, water vapour has nowhere to go and it condenses on the coldest surface it can find. If you kept the garage door (Option 1), that cold surface is the back of the door, and you will get the same fogging and dripping that plagues unfinished garages every Ontario winter. Our guide to garage door condensation explains the physics and the fixes. The solution in a conversion is a proper vapour barrier on the warm side of the insulation, adequate mechanical ventilation, and, where the door stays in place, keeping an air gap and a path for that cavity to dry.

Heating, Ventilation, and the Carbon Monoxide Question

A converted garage still shares a wall, and sometimes a floor or attic, with the rest of the house, and if the garage is attached, it may also share space with a furnace, a water heater, or a car parked in the remaining bay. That makes air quality a real design item, not an afterthought.

Extending your existing forced-air system into the new room is often the cleanest option, but it is not always allowed or practical. Adding a register to a garage-turned-bedroom can violate code if any part of the space still functions as a garage, because you do not want ductwork moving air between a space that may contain vehicle exhaust and a sleeping area. Many conversions instead use a dedicated heat source such as a ductless mini-split heat pump, which also handles summer cooling and dehumidification in one unit.

If any portion of the structure remains a garage, or if fuel-burning appliances are nearby, carbon monoxide protection becomes essential. Ontario law requires working CO alarms near sleeping areas in homes with an attached garage or a fuel-burning appliance, and a conversion that adds a bedroom next to a garage is exactly the scenario the rule exists for. Our article on carbon monoxide risk in an attached garage covers where alarms go and why the shared wall between house and garage has to be sealed and fire-separated. Treat this as a must-do, not a nice-to-have.

Egress, Light, and Ceiling Height

If the new room will ever be used or sold as a bedroom, it has to meet the Building Code requirements for a habitable room, and this is where many informal conversions fail an inspection. A bedroom needs an egress window large enough to climb out of in a fire, positioned low enough to be usable, which is one of the main reasons the door opening usually gets a real window rather than a blank wall. Habitable rooms also have minimum requirements for natural light, ventilation, and ceiling height, and that last one is why raising the floor over the cold slab has to be balanced against how much headroom you started with.

None of this is meant to scare you off. These are the same rules that make the rest of your house safe and comfortable. The point is that a garage was not built to habitable-room standards, so a proper conversion is the work of bringing it up to them. A building official is not your adversary here; they are the person who confirms the family bedroom you just built is safe to sleep in.

Realistic 2026 Costs in the London Area

Prices on this page are before HST.

Costs vary enormously with scope, so treat these as planning ranges for southern Ontario in 2026, not quotes. The single biggest variable is whether you are building a heated hobby room or a code-compliant habitable room with egress, insulation, HVAC, and a finished exterior.

• Insulated stud wall behind an existing door (Option 1), materials and labour: roughly $1,500 to $4,000, depending on wall size and finish.
• Remove door and frame an insulated exterior wall with a window (Option 2): roughly $4,000 to $9,000 for the opening alone, before flooring, HVAC, and interior finishing, and more if the brick or siding is difficult to match.
• Full-view glass wall or patio-door swap (Option 3): roughly $4,000 to $12,000 depending on the glass system and structural work.
• Floor build-up over the slab (moisture barrier, rigid foam, subfloor): roughly $6 to $14 per square foot installed.
• Ductless mini-split heat pump for heating and cooling: roughly $3,500 to $6,500 installed for a single-zone unit.
• Complete garage-to-living-space conversion, permitted and finished: commonly $20,000 to $60,000-plus for a double garage, driven mostly by whether it is a simple room or a full secondary suite with plumbing.

Two notes. First, a legal secondary suite with a kitchen and bathroom is a different animal from a finished family room, and its plumbing, fire separation, and separate-entrance requirements push it toward the top of these ranges. Second, if you later decide to put a door back, budget for that separately; reinstalling a garage door and opener is its own line item, and our Ontario garage door cost guide covers current pricing for a new door and installation.

The Reversibility Question: Protecting Resale Value

This is the decision homeowners most often get wrong, and it is worth slowing down for. A garage is a feature buyers actively want in Ontario, both for parking in a climate with real winters and for storage. Appraisers and agents frequently value a functional garage more than the equivalent square footage of a converted room, especially a room that obviously used to be a garage. Convert badly, or convert without a permit, and you can lose value even after spending tens of thousands of dollars.

Three principles protect you. First, permit the work, so the space counts as legitimate finished area and does not become a disclosure problem at sale. Second, build it to look like it was always a room, because a conversion that reads as "sealed-up garage door with a window stuck in it" advertises its own origins and its own compromises. Third, think hard about reversibility. If your neighbourhood is one where every comparable home has a garage, keeping the conversion reversible (Option 1, a stud wall behind an intact door) lets a future buyer put the garage back, which can be worth more than the finished room itself.

The size and layout of your remaining parking and storage matters too. If you have a single garage and you convert it, you have no garage; if you have a double and convert one bay, you keep a functional single. Our comparison of a single versus double garage door is a useful lens for thinking about how much you are giving up and what a future buyer will notice.

Common Mistakes Homeowners Make

Skipping the permit to save time

The most expensive shortcut in the whole project. Unpermitted habitable space can force you to open finished walls later, complicate or kill a sale, and expose you to fines. The permit also gives you an inspector who catches the insulation and egress problems while they are still cheap to fix.

Ignoring the floor

People insulate the walls, paint beautifully, lay a nice floor directly on the cold slab, and then wonder why the room is freezing and the flooring cups within a year. The slab is the number-one comfort problem in a garage conversion and it has to be addressed with a proper insulated build-up.

Sealing the space without solving moisture

Turning a vented garage into a sealed room without a vapour barrier and mechanical ventilation is how you grow mould inside a brand-new wall. Air-tightness and moisture management are two halves of the same job.

Building an irreversible conversion in a garage-loving market

If comparable homes on your street all have garages, permanently removing yours can cost you more at resale than the finished room adds. In those neighbourhoods, a reversible conversion is often the smarter financial play.

Forgetting carbon monoxide and fire separation

Any conversion that leaves part of the structure as a garage, or that adds a bedroom near an attached garage, has to take CO alarms and the fire-rated separation between house and garage seriously. This is a safety line, not a formality.

Frequently Asked Questions

Do I need a permit to convert my garage into a room in Ontario?

In almost every case, yes. Converting a garage to habitable space is a change of use under the Ontario Building Code, and the province's own guidance says a change-of-use permit can be required even without construction. The application goes to your municipality, which for our service area is the City of London building department, and it also triggers a zoning check that can affect required parking. Confirm before you start.

Should I keep the garage door or remove it?

It depends on the goal. For a heated hobby room or gym where reversibility matters, build an insulated wall behind the existing door and leave it in place. For a true bedroom, office, or family room that must feel like part of the house and meet egress rules, remove the door and frame a proper insulated wall with a window. There is no single right answer; there is a right answer for your use and your neighbourhood.

Will converting my garage hurt my home's resale value?

It can, if done poorly or without a permit, because many Ontario buyers specifically want a functional garage. A permitted, well-finished conversion that does not obviously read as a former garage protects value best, and keeping the work reversible protects it further in neighbourhoods where garages are the norm. A rough, unpermitted conversion usually subtracts value.

Why is my converted garage always cold?

Almost always the floor. A garage slab is poured on grade with little or no insulation and stays cold year-round, radiating that cold upward regardless of your heating. Insulating the walls and ceiling but laying flooring straight on the bare slab is the most common reason a converted garage never feels warm. The fix is an insulated floor build-up over a moisture barrier.

Can I just heat the space with the door still on?

You can heat it, but you will fight condensation on the back of the cold door and lose a lot of that heat straight through the thin steel. If you keep the door, build an insulated wall behind it with a vapour barrier and a way for the cavity to dry, and expect the room to be less comfortable than one where the opening was properly walled and insulated.

What about carbon monoxide if the garage is attached?

Take it seriously. Ontario requires working CO alarms near sleeping areas in homes with an attached garage or fuel-burning appliances, and the shared wall between the house and any remaining garage space must be sealed and fire-separated. A conversion that adds a bedroom beside a garage is precisely the situation these rules protect against.

Can I put the garage door back later?

If you planned for it, yes, and that is the whole appeal of a reversible conversion. Leaving the door, tracks, and header intact behind a removable stud wall makes reinstating the garage a modest job. If you fully removed the opening and framed a permanent wall, putting a door back means new structural work, a new door, and a new opener, which is a full installation cost.

Conclusion

A garage conversion can be one of the highest-value renovations a London homeowner makes, turning the biggest underused room in the house into an office, a suite, or a bedroom for family. The projects that succeed all share the same trait: they treat the garage door opening as the central decision, not an afterthought. Get the permit, decide honestly whether you are building a reversible hobby room or a permanent habitable space, solve the cold slab and the moisture before you finish anything pretty, respect the heating and carbon-monoxide rules that come with an attached garage, and think about what a future buyer will want to see. Do those things and the room will feel like it was always part of the house.

If your conversion plan involves removing, replacing, or reinstating a garage door, that is our corner of the project and we are happy to advise on it. Whether you want a full-view glass wall that keeps the light, a clean removal so your builder can frame the opening, or a brand-new door and opener to put the garage back, call 519-619-7901, reach us through our contact page, or price a new door on our price estimator. AA Advantage Doors has served London and area since 2009, and our BBB profile has our track record.