7 Tips for Multi-Family High-Rise Commercial Flat Roofing

Commercial roofing installers for high rise apartments in Toronto

Whether you plan to invest in a new multi-family high-rise building or upgrade an existing one, the high-rise commercial flat roofing will affect the lives of your tenants or condominium owners and significantly alter your return on investment.

Multi-family housing is an important market in the Toronto area, with drivers including the flexibility that renting offers, millennial preferences, and the often unattainable pricing of single-family homes. Roof leaks in multi-family high-rise buildings have high implications. A single leak in the commercial roof could potentially affect not just the top floor, but the units beneath it as well.


Special Considerations for Multi-Family High-Rise Commercial Roofing

Elite Roofing is no stranger to working on commercial multi-family buildings in Toronto, including high-rises over ten stories tall, many of which are several decades old or more. With the average life of a roof being approximately 20 years (with proper maintenance), many of these buildings come due for upgrades or replacement of their roofs each year. 

Advances in roofing technologies and materials have opened up a wide range of innovative roofing choices. All property owners should consider the factors below when planning future roofing upgrades or replacements. This is regardless of building specifications, budget, and other criteria.


1. Noticing and reporting leaks

Leaks may take a long time to become apparent. This is especially true in situations where there is a solid substrate (such as concrete) and where there is also a good vapour retardant in place, so vigilance is key. When water leaks through a hole in the membrane, it can saturate and soil a large section of the insulation over time before finally reaching a penetration in the substrate created for fan housings, roof drains, plumbing vent stacks, roof access hatches, elevator mechanical rooms, and/or other areas. Leaks like these can also spread quite far from the initial point of penetration through the roof membrane. Early leak detection and regular maintenance inspections are critical to keeping small problems from growing into larger ones.


Tips for Multi Family High Rise commercial flat roofing in Toronto
Penetration into the metal counterflashing and membrane upturn for an AC condenser unit copper line set. This is a potential source of leaks into the building.

2. High-Rise commercial flat roofing design criteria 

Unlike a single-story property, the payback of putting upgraded insulation on high-rise commercial flat roofing is generally limited. This is because heat rises upward and the top level can remain warm as a result. On the other hand, the top floor is more exposed to high winds, so it should be well-insulated.

As an alternative to typical built-up flat roofing systems used for flat high-rise roofs, we often consider installing inverted roofing systems. In these assemblies, the membrane sits directly over the substrate. It is protected by closed-cell insulation (such as extruded polystyrene), filter cloth, and ballast. Inverted roofing can prolong a high-rise roof’s life expectancy more than other systems by providing protection from direct exposure to weather elements [such as UV rays] and traffic [such as the use of the roof as a staging platform for restoration work].  

See Case Study on Inverted Roofing here.


3. Damage-protection and inverted roofing systems

Roofs of older high-rise buildings often require upgrades and restoration. Projects such as concrete and masonry repairs, replacing balconies, and installing railings often involve setting up a swing stage for safe access as well as heavy foot traffic from construction staging. These situations can lead to extensive roof damage and deterioration. The durability and long life cycle of inverted roof systems add an extra layer of protection. 


Tips for Multi Family High Rise commercial flat roofing
Displaced ballast, torn filter cloth and exposed XPS insulation on a high rise residential building with an inverted roof assembly

4. Wind effects

High-rises are negatively affected by Toronto’s high winds. This often results in displaced gravel, wind-swept corners on ballasted roof systems, and the risk of metal blow-off. Roofers must pay special attention to ensure that rooftop items and metal installations are properly anchored or secured.  These important items are likely to turn up during periodic roof inspections.


5. Building envelope issues

In Toronto, a building’s eastern elevation takes extra abuse due to wind-driven rain that often comes from the east direction. Masonry that sits above the roof line, such as on stairwell penthouses and elevator mechanical room walls, is a common source of water infiltration. Pay special attention to these and other areas that are prone to water soaking through the masonry, running along the concrete slab, and seeping into the roof assembly. This can trigger leaks and soil roof insulation. Also consider metal cladding as a potential solution for the effects of water penetration on a building’s eastern elevation. 


Tips for Multi Family High Rise commercial flat roofing
Attempt to temporarily repair damaged/leaking masonry with elastomeric sealant

6. Hallway fan housing units

The hallways of most multi-family high-rise buildings in Toronto are ventilated by fan-housing units that maintain airflow. Landlords should attend to their ongoing maintenance and repair. This is to prevent them from becoming a source of leaks or allowing for excessive moisture to build up inside the corridors. Regularly check on the need to repair or replace components such as belts and motors, sheet metal housings, side louvres and dented, loose, or missing housing covers. 


7. Roof Anchors

To ensure safety while performing work on the roof or building exterior, Canada’s building code requires that multi-story buildings are equipped with fixed anchor points. Many older buildings lack anchors, which must be installed before roofing work begins to assure legal compliance and protection of workers.

For more information read: Everything You Need to Know About Roof Anchors.

We also recommend scheduling roof and roof anchor inspections before the start and after the completion of major restoration projects.


Protecting your high-rise commercial flat roofing investment

How can you get the most value from your investment in a multi-family high-rise? One way is to optimize your flat roof, taking into consideration the seven points above. It’s also essential to choose a roofing company with experience, ongoing maintenance and repairs, and schedule semi-annual professional roofing inspections.

Follow these steps to ensure optimal performance from your roof, protect your property, and add value to your real estate investment. Contact Elite Roofing in Toronto for the roofing expertise you need for your high-rise commercial flat roofing.