Commercial Green Roof: What Ontario Requires Now
Toronto's green roof bylaw is no longer in effect. Here is what changed, what still applies and what a roof needs before plants go on it.
Call 1-833-775-7663 Oakville head office · Flat roof systems, green roofs, repairs and inspections for commercial, industrial and institutional buildings across Ontario
Karol Rajkowski
Vice President, OYH Roofing
Published October 12, 2026 · 12 min read
Short answer
A commercial green roof in Ontario is now a choice, not a requirement. Toronto's Green Roof Bylaw has not been in effect since November 3, 2025. A green roof still needs a building permit in Toronto, an engineer's review of the structure, and a root-resistant, leak-tested membrane, and Toronto still pays $100 per square metre toward one.
Is the Toronto green roof bylaw still in effect?
No. Toronto's Green Roof Bylaw has not been in effect since November 3, 2025, when Ontario repealed the section of the City of Toronto Act that allowed it. A commercial green roof on a private building in Toronto is now voluntary.
The legal step was a proclamation. Section 108 of the City of Toronto Act, 2006 had carried its own repeal clause since 2006, and Order in Council 1374/2025 named November 3, 2025 as the day it took effect. The City's planning summary says the bylaw "is therefore no longer in effect", and Toronto Building no longer asks for the Green Roof Declaration Form with a permit application.
Bill 98, the Building Homes and Improving Transportation Infrastructure Act, 2026, went further on June 2, 2026. It removed sustainable design from site plan control across Ontario and added wording to the Building Code Act that keeps construction standards for the protection or conservation of the environment out of municipal by-laws. The Toronto Green Standard now lists its green and cool roof measure as voluntary for applications made on or after that date.
| Date | What happened | Source |
|---|---|---|
| May 27, 2009 | Toronto Council adopts the Green Roof Bylaw | Municipal Code Chapter 492 |
| January 31, 2010 | The rule starts for new buildings and additions of 2,000 m² or more | Chapter 492 |
| April 30, 2012 | Industrial buildings are added | Chapter 492 |
| November 3, 2025 | Section 108 of the City of Toronto Act is repealed by proclamation; the bylaw is no longer in effect | Order in Council 1374/2025 |
| June 2, 2026 | Bill 98 receives Royal Assent and removes environmental construction standards from municipal by-laws and site plan control | S.O. 2026, c. 8 |
| Today | Green roofs are voluntary on private buildings; City-owned buildings keep a 50 per cent green roof standard | City of Toronto |
While it was in force, the bylaw required a green roof on 20 to 60 per cent of the available roof space of new buildings and additions with a gross floor area of 2,000 m² or more. Industrial buildings had a lighter rule, and owners could pay cash in lieu at $200 per m². It never applied to re-roofing an existing building. The City counts more than 1,200 green roofs built during those 15 years.
One loose end remains. The bylaw text is still posted on the City's website, and some City pages still describe its requirements in the present tense. Go by the dated statements above, and ask Toronto Building if your project was already under review in November 2025.
What rules still apply to a commercial green roof?
A building permit in Toronto, the Building Code everywhere in Ontario, and the terms of the roof warranty. The bylaw is gone, but a green roof is still a heavy load on the structure and a buried membrane, and both are regulated.
| Rule | What it asks for | Source |
|---|---|---|
| Building permit (Toronto) | Required for a new green roof, or a material change to one, on new and existing buildings | Toronto Building |
| Wind uplift report | From a professional engineer, filed with the permit application | Toronto Building |
| Leak test report | A successful test before the green roof goes on, signed by an architect or engineer | Toronto Building |
| Maintenance plan | Filed with the permit application | Toronto Building |
| Root resistance | Waterproofing in a vegetated roof must resist roots when tested to ANSI/GRHC/SPRI VR-1 | National Building Code 2020, 5.6.1.2. |
| Structural load | Soil and plants count as dead load, with a higher load factor for saturated soil | National Building Code 2020, Part 4 |
| Guards | At least 1,070 mm high around a roof that people use for more than maintenance | National Building Code 2020, 3.3.1.18. |
| Other Ontario cities | The Mississauga, Oakville and Brampton permit pages do not mention green roofs; ask the building department | Municipal permit pages |
Toronto's stand-alone permit fee for a green roof, effective January 1, 2026, is $0.76 per m² without structural work and $6.20 per m² with it. Toronto Building says it still reviews plans against the Toronto Green Roof Construction Standard, the technical part of the old bylaw. Treat that standard as the best Ontario reference for design, even outside Toronto: it sets out the layers, a saturated growing medium density of 2,000 kg per m³ for load calculations, a root barrier in every system and a leak test before planting.
Our roof replacement permit guide covers the other roof work that needs a permit in Toronto, Mississauga and Brampton.
What are the types of green roofs?
There are three: extensive, semi-intensive and intensive. Extensive roofs are shallow, light and planted with sedums and grasses. Intensive roofs are deep, heavy rooftop gardens, and semi-intensive roofs sit between the two.
| Type | Growing medium | Weight when saturated | Typical use |
|---|---|---|---|
| Extensive | Under 200 mm (NRC); 152 mm or less (SPRI) | Under 300 kg/m² (NRC); 63 to 146 kg/m² (SPRI) | Sedums, herbs and grasses; entered only for maintenance |
| Semi-intensive | A mix of shallow and deeper areas | 122 to 195 kg/m² (SPRI) | A wider choice of plants |
| Intensive | Over 200 mm (NRC) | Over 300 kg/m² (NRC); 171 to 488 kg/m² (SPRI) | Accessible gardens with irrigation and regular care |
For most existing commercial roofs, extensive is the realistic choice. NRC notes that many existing buildings can take an extensive green roof because its loads are low, while intensive roofs are normally designed into a new building. A Toronto and Region Conservation Authority (TRCA) survey of extensive systems sold in Canada found saturated weights from about 39 to 244 kg/m² (8 to 50 lb per sq ft).
What should be checked before a commercial green roof goes on?
Seven things: the structure, the age of the membrane, root resistance, a leak test, drainage, wind and fire design, and who will maintain it. The structural review comes first, because a saturated green roof is far heavier than the loads most roofs were designed to carry.
| Check | What it involves | Who says so |
|---|---|---|
| 1. Structure | An engineer confirms the deck and frame can carry the saturated system with snow, rain and maintenance loads | Toronto Building, NRC, SPRI |
| 2. Membrane age | A buried membrane cannot be inspected or dry out, so an aging membrane is replaced first | Toronto guidelines; our practice |
| 3. Root resistance | A root-resistant membrane or a separate root barrier in every system | Building Code, Toronto standard |
| 4. Leak test | Electronic leak detection or a flood test before the growing medium goes on | Toronto standard, ASTM D8231, NRC |
| 5. Drainage | Positive slope to the drains, overflow scuppers and plant-free zones around every drain | Toronto standard |
| 6. Wind and fire | An engineer's wind uplift design, and plant-free borders of at least 0.5 m beside combustible-clad walls and equipment | Toronto standard, CSA A123.24 |
| 7. Maintenance | A written plan, watering in the first season, at least two inspections a year and clear drains | TRCA, SOPREMA, Toronto standard |
Toronto's guidance calls green roof loads large compared with normal roof design loads, and asks designers to allow for snow drifting around the plantings. TRCA found that one-storey industrial buildings with wide column spacing would normally need added support, although only one of 18 Greater Toronto Area installations it surveyed needed structural changes. Our flat roof snow load guide lists the design snow loads for 23 Ontario areas.
Find leaks before the plants arrive. ASTM's guide to electronic leak detection notes that overburden such as a vegetated roof makes leaks much harder to locate, and Toronto's guidelines point out that infrared scans are of no use once the green roof is on. Electric field vector mapping can retest a planted roof, but the same guidelines say it is not compatible with EPDM. Our commercial roof inspection guide explains the survey methods.
Thinking about a green roof?
We will look at the roof you have, tell you what the membrane and the structure need first, and give you a written quote.
Call 1-833-775-7663Request an assessmentWhich roof membrane goes under a green roof?
Any of the common low-slope membranes can go under a commercial green roof, as long as the assembly resists roots and is built to a higher standard than an exposed roof. Two-ply SBS modified bitumen, TPO, PVC and EPDM are all used.
Toronto's guidelines suggest at least two plies for modified bitumen and a slope to the drains above the code minimum, because the membrane is hidden and cannot dry. Root barriers are usually PVC, TPO or polyethylene sheet, and NRC notes that the root-resistant layer can also be an agent built into the membrane. Warranties matter more than usual: SOPREMA's vegetated roof warranty, for example, covers removing and reinstalling the planted system when a covered leak is repaired. Ask what yours covers before planting.
OYH Roofing installs all four membranes. Our comparisons explain where each one fits: modified bitumen vs TPO, PVC vs TPO and TPO vs EPDM. If the existing membrane is near the end of its life, our commercial flat roof lifespan guide explains why it should be replaced before anything is built on top of it.
What does a green roof do for a commercial building?
It holds back stormwater, keeps the membrane cool in summer and cuts heat gain through the roof. In Canadian studies the winter benefit is small, so a green roof is mainly a stormwater and summer cooling measure.
| Measure | Result | Where |
|---|---|---|
| Stormwater runoff | 63 per cent less than a conventional roof outside January to March; 51 to 54 per cent estimated over a full year | York University, Toronto (TRCA) |
| Stormwater runoff | 57 per cent less on average over the year | Eastview Community Centre, Toronto (NRC) |
| Membrane temperature | About 25°C under the green roof against 70°C on the exposed membrane on a summer day | Ottawa (NRC) |
| Summer heat flow through the roof | Down by more than 75 per cent | Ottawa (NRC) |
| Winter heat loss | No difference from November to February | Ottawa (NRC, five years of data) |
A cooler, shaded membrane should last longer. NRC measured a typical daily temperature swing of 6°C under the green roof against 45°C on the exposed membrane in spring and summer. No Canadian study has measured how many extra years that buys, so treat longer membrane life as likely, not proven. If summer heat is the main concern, a reflective roof does part of the same job for far less weight; see our cool roof guide.
What incentives and credits are there for green roofs in Ontario?
Toronto pays $100 per square metre of green roof, up to $100,000 a project, through its Eco-Roof Incentive Program, and some cities, such as Mississauga and Waterloo, reduce stormwater charges for properties with green roofs. We found no provincial or federal program that names green roofs on commercial buildings.
| Program | What it offers | Conditions |
|---|---|---|
| Toronto Eco-Roof Incentive Program | $100 per m² of green roof, up to $100,000 per project; up to $1,000 toward a structural assessment | Existing residential, industrial, commercial and institutional buildings; green roof on 20 to 60 per cent of available roof space, depending on building size; building permit in hand; approval before any work starts |
| Mississauga stormwater charge credit | Up to 50 per cent off the stormwater charge | Non-residential and multi-residential properties; an engineer's report; green roofs are named in the City's guide |
| Waterloo stormwater credit | Up to 45 per cent | Green roofs are named under quantity control |
| Toronto stormwater charge | None to reduce | Council suspended work on a stormwater charge on February 5, 2025 |
The Eco-Roof pages have not been rewritten since the bylaw lapsed and still refer to it, so confirm the current terms with the City before you set a budget. The same program pays $5 per m² for a reflective membrane and $2 per m² for a reflective coating; our commercial roof coating guide covers when a coating is the right call.
What are the downsides of a green roof, and what does one cost?
Weight, cost, upkeep and harder leak repairs. A commercial green roof costs more to build and to maintain than a conventional roof, and it pays back only where stormwater control, summer cooling or an incentive matters to the owner.
- Weight. The structure has to be checked by an engineer and sometimes reinforced.
- Buried leaks. A leak under the growing medium is harder to find and costlier to reach.
- Upkeep. Tree and shrub seedlings can damage the waterproofing, and blocked drains pond water. SOPREMA asks for at least four visits a year on an extensive roof.
- Plants. Drought, overwatering and wind scour at corners and edges all kill plants.
- Winter. The energy benefit is small in the heating season.
We do not publish green roof prices, because structure, access and the planting system change them too much. The public figures are old. A TRCA and University of Toronto study, using 2010 Toronto prices, put a new 2,000 m² extensive green roof, membrane included, at $231,278 to $472,909, and TRCA's 2007 analysis found a life-cycle cost about 1.56 times that of a conventional roof. Prices have risen since, so get a written quote after the structural review.
How does OYH Roofing approach green roofs?
We start with the roof under the plants. OYH Roofing offers green roof systems as part of its flat roofing work on commercial, industrial and institutional buildings in Ontario, and the first steps are always the same: an engineer's review of the structure, an honest look at the membrane, and a leak test before anything is planted.
You can see the membranes we install on the completed projects page, including the 52,300 sq ft modified bitumen roof at 777 Niagara St in Welland and the Marriott Hotel in Vaughan. Our guide on how to choose a commercial roofing contractor lists the questions to ask any bidder.
Frequently asked questions
Was the Toronto green roof bylaw repealed?
In effect, yes. On November 3, 2025 Ontario repealed section 108 of the City of Toronto Act, the section that let Toronto require green roofs, and the City says its Green Roof Bylaw is no longer in effect. We found no Council vote repealing the bylaw text, which is still posted, but it no longer applies to building permits. Green roofs on private buildings are voluntary.
Do I need a permit to install a green roof in Toronto?
Yes. Toronto Building requires a building permit for a new green roof, or a material change to one, on both new and existing buildings. The application needs a professional engineer's wind uplift report and a maintenance plan, and a leak test report signed by an architect or engineer is needed before the green roof goes on. Ask other Ontario cities directly.
What are the three types of green roofs?
Extensive, semi-intensive and intensive. Extensive roofs have a shallow growing medium, usually under 150 to 200 mm, planted with sedums and grasses, and they are the lightest. Intensive roofs are deeper, heavier rooftop gardens that need irrigation and regular care. Semi-intensive roofs combine the two. Most green roofs added to existing commercial buildings are extensive because of the weight.
What are the downsides of a green roof?
Weight, cost and upkeep. A saturated green roof is much heavier than a conventional roof, so an engineer has to check the structure, and some buildings need reinforcing. It costs more to build, needs planned maintenance every year and makes leaks harder to find and repair because the membrane is buried. In Canadian studies it also does little for winter heating.
What is the lifespan of a green roof?
There is no measured Canadian figure. A green roof shades the membrane and keeps it far cooler in summer, so the membrane is expected to last longer than an exposed one, but National Research Council Canada measured temperatures, not service life. The plants and growing medium last as long as they are maintained, and the membrane underneath should be new or sound before it is covered.
What are the requirements for a green roof?
A structure that can carry the saturated system, a waterproof membrane that resists roots, a drainage layer, a growing medium and plants, plus a leak test before planting and a maintenance plan. In Toronto a building permit is required, with an engineer's wind uplift report. Since November 3, 2025 Toronto no longer requires a green roof on private buildings.
Planning a green roof or a new membrane?
Call for an assessment of the roof and a written quote for the work it needs first.
Call 1-833-775-7663Request an assessment
Karol Rajkowski
Vice President · OYH Roofing
Karol Rajkowski is Vice President of OYH Roofing, an Oakville-based ICI flat-roofing contractor whose projects include the City of Mississauga building at 3185 Mavis Rd and the Marriott Hotel in Vaughan. Learn more about the OYH team.
Sources
- Schedule: Order in Council 1374/2025, Government of Ontario, November 6, 2025.
- City of Toronto Act, 2006, section 108, and Building Code Act, 1992, section 35, Ontario e-Laws.
- Bill 98, Building Homes and Improving Transportation Infrastructure Act, 2026, Legislative Assembly of Ontario, and the decision notice 026-0300, Environmental Registry of Ontario, June 9, 2026.
- City of Toronto: How Ontario's Planning Rules Have Changed, July 2026; City of Toronto Green Roof Bylaw page, modified November 12, 2025; Municipal Code Chapter 492, Green Roofs; and Toronto Green Standard Version 4: Ecology and Biodiversity, modified August 24, 2026.
- Green Roof on a New or Existing Building, Toronto Building, modified September 8, 2026, and the Toronto Green Roof Construction Standard: Supplementary Guidelines, City of Toronto.
- O. Reg. 163/24: Building Code, Ontario e-Laws, and the National Building Code of Canada 2020, National Research Council Canada.
- Using Garden Roof Systems to Achieve Sustainable Building Envelopes, Construction Technology Update No. 65, NRC, 2005, and NRC green roof research, 2009.
- TRCA Sustainable Technologies Evaluation Program: Green roofs for stormwater management, technical brief; Eastview green roof report, NRC and City of Toronto, 2005; An Economic Analysis of Green Roofs, 2007; life cycle costs of low impact development practices, 2013; and the green roofs and inspection and maintenance pages of the STEP wiki.
- SPRI: ANSI/SPRI VF-1 2023, External Fire Design Standard for Vegetative Roofs, and ANSI/SPRI RP-14 2022, Wind Design Standard for Vegetative Roofing Systems.
- CSA A123.24:21, Standard test method for wind resistance of vegetated roof assembly, CSA Group.
- ASTM International: D7877-25 and D8231-24a (electronic leak detection).
- SOPREMA: Sopranature brochure, November 2025, and Sopranature maintenance guide.
- Incentives and credits: Eco-Roof Incentive Program and its terms and conditions, City of Toronto; stormwater charge credit program, City of Mississauga; stormwater credit, City of Waterloo.
- Municipal permit pages: Mississauga, Oakville and Brampton.
- OYH Roofing project records: 777 Niagara St, Welland; Marriott Hotel, Vaughan; residential building, Sault Ste. Marie (October 2026).
OYH Roofing, 2120 Speers Rd, Oakville, ON L6L 2X8 · 1-833-775-7663 · info@oyhroofing.ca