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Francis Guertin

by Francis Guertin Renovation Advisor| Reno-Assistance

Reno Blog / Roof / Flat Roofs: What Material Should You Choose?
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Flat Roofs: What Material Should You Choose?

Advice Cost and Price Roof

EPDM, TPO, Elastomer, Polyolefin…What do these words/letters even mean? These acronyms surely won’t tell you much in regards to which roofing option is best suited for you. 

That’s why we’ve put together all you need to know about flat roofs. You’ll be able to make a sound decision – whether it be for your home’s roof or a commercial roofing project. There isn’t a one-size-fits-all kind of roofing material out there, so you’ll need to take a look at the pros & cons of each flat roof material. Even if the price is important, keep in mind that the least costly option might not necessarily be beneficial in the long run. 

The elastomeric membrane or modified bitumen

This double-layered membrane consists of having a first membrane applied and welded down with a blowtorch. It’s then covered with a membrane that has sand-like (or asphalt shingle-like) particles on it. These particles essentially replace the old gravel roofing that’s likely to be found on your flat roof. When looking to hire a roofer to install an elastomeric membrane, make sure they have the correct insurance policies needed as installing this material is a fire hazard. Also, note that some contractors might forget to seal some joints (like those near skylights or ventilators), which will lower this roofing’s lifespan, hence the importance of hiring a highly qualified roofer. 

An elastomeric membrane can also be used for resurfacing, which allows you to lower waste and lessen your environmental impact. Resurfacing consists of heating up the older membrane, pushing in the leftover particles, and installing a new membrane on top.

If you’re planning on putting in a rooftop terrace, an elastomeric membrane should be your material of choice. It has all the characteristics needed and can be walked on without causing any damages. Its resistance also makes it the top roofing material choice for Canadian residents. 

Pros of an elastomeric membrane:

  • Requires little to no maintenance;
  • Resistant to wear and tear caused by branches or other debris.

Cons of an elastomeric membrane:

  • Slightly more costly than asphalt and gravel roofing

Take a look at our elastomeric membrane roofing page to learn more. 

roofer applying a membrane with a blowtorch

TPO

Thermoplastic Polyolefin (TPO) is a single-layered membrane. This kind flat roof material is heat-welded with a hot air machine, eliminating the risk of fire – as opposed to an elastomeric membrane. Though, it’s important to note that, since only one layer is applied, it’s prone to water infiltration if it isn’t properly installed. Seeing as TPO doesn’t require much equipment when installed, in comparison to other roofing materials, many contractors offer this kind of roofing solution. It’s therefore important to hire a roofer for his qualifications and not so much for his price quote. 

Of all the petrol-based roofing solutions, the TPO membrane is the least polluting option. Plus, it’s entirely recyclable at the end of its lifetime. TPO is also more aesthetic than other solutions as it’s available in many colours, including white – which reduces the urban heat island effect. However, manufacturing TPO does require more energy. 

Pros of TPO roofing:

  • Highly resistant to UV rays, heat, and extreme weather conditions.

Cons of TPO roofing:

  • Its surface can easily deteriorate;
  • Not as resistant to extreme cold as other solutions;
  • Its official lifespan is unknown (fairly new material);
  • Easily damaged (perforated). 

roofer installing a tpo membrane

EPDM

EPDM stands for Ethylene Propylene Diene Monomer. It’s essentially a synthetic rubber! This flat roof material is equally resistant to extreme colds as it is to strong UV rays. It’s also resistant to high humidity levels. Its characteristics are fairly similar to those of the TPO membrane. Though, besides being recyclable, it can be made of fully recycled materials – greatly reducing its environmental impact. 

Pros of EPDM roofing:

  • Entirely recyclable;
  • Highly resistant to UV rays;
  • Keeps its elasticity in extreme colds.

Cons of EPDM roofing: 

  • Installation must be done elegantly;
  • Damages can be difficult to spot;
  • Easily damaged (perforated). 

Looking to learn more on TPO & EPDM roofing? Take a look at our TPO & EPDM roofing page! 

"I'm here to help you with your roof project"

- Francis / Renovation Advisor at Reno-Assistance

Tar and Gravel

Asphalt and gravel roofing is a multi-layered roofing solution for your flat roof that’s basically a sheet of felt that’s soaked in asphalt. The multi-layered lining is useful in reducing the risks of water infiltration. This kind of roofing can be long-lasting, but it’ll need to be maintained and inspected fairly regularly. For instance, it’s important to make sure that there’s gravel covering up the entire surface to ensure the felt sheet doesn’t dry out when because of sun exposure. In older Toronto districts, many flat roofs have this as a roofing solution. However, more and more people are opting for single-layered flat roof options. An increasing number of municipalities are forbidding the use of tar and gravel as a roofing solution. Be sure to consult your city rules & regulations.

It’s quite noticeable when it’s time to get this kind of roofing replaced. For example, if you notice craters, dust accumulation, or even when a large portion of the felt is exposed. When the gravel begins to detach from the surface, a professional will need to coat the roof with a liquid solution and add more gravel. 

Pros of tar and gravel roofing:

  • Lower material cost compared to other roofing solutions;
  • Easy to repair.

Cons of tar and gravel roofing: 

  • Maintenance is quite tedious;
  • Proper installation conditions aren’t available (weather needs to be taken into consideration, the asphalt’s temperature as well, how thick it is, etc.);
  • Limited expansion and contraction (elasticity) capabilities.

gravel rooftop on red building

Why not get a green roof? 

Two kinds of green roofs exist; extensive roofs (without cultivation), and intensive roofs (with cultivation crops). In either case, you’ll need to make sure a drainage system is installed. Extensive roofs are much easier to install as they simply require a thin layer of loam (fertile soil), making the workload lighter. Intensive roofs, on the other hand, need at least 6 inches of soil, making it a lot heavier for contractors. Also, costs associated with intensive roofs are higher as the roof needs to be easy to access, requiring more work to be done – i.e. installing a stairwell, a door, etc.. For both roofs, the help of a structural engineer is required as the building’s structure will need to be reinforced. 

Although the initial cost of a green roof might be quite high, it’ll be well worth it. You’ll save on heating and cooling costs thanks to the insulation effect created by the soil on the roof. The overall air quality will be improved too since the CO2 you exhale will be absorbed by the plants. The best part? Your roofing material is protected by the loam, doubling its lifespan! 

What about a rooftop terrace? 

Putting in a rooftop terrace is also an interesting option, especially if you already put in a green roof! Rooftop terraces are popular in more urban settings, where open land is limited, or nonexistent. You can put in a patio set, a pergola, put in little passageways through your crops, etc. The possibilities are practically endless! Just be sure you hire highly qualified contractors to ensure everything is properly installed and fixed into the structure (ensuring they won’t fly away with extreme winds). Of course, you’ll need to make sure there’s a drainage system in place!

Have a rooftop terrace project in mind?

White roofs – what are they all about? 

White roofs are used to offset the urban heat island effect. However, there’s quite some debate regarding its true efficiency. Also, as the roof doesn’t attract the sun’s rays, you’re likely to have higher energy bills in colder months. Another inconvenience would be that, in no time, your white roof is likely to turn grey, losing between 30% and 60% of its sun reflecting capabilities. 

Is covering existing roofing with another material feasible?

Tar and gravel roofing can be covered up with a different kind of flat roof material. The gravel must first be removed, and then MDF sheets need to be installed before recovering the surface with the new material. However, doing so isn’t recommended as the humidity stays trapped between the layers and can cause damages. 

How much does it cost to replace a flat roof? 

Below is a table with the average costs to replace a flat roof in both Greater Montreal & Greater Toronto, along with these roofing systems’ typical lifespans.

Roof Type Average Cost –  Montreal

Average Cost –Toronto (GTA)

Lifespan
Elastomeric Membrane $8.40 – $13.65/sq. ft. $9.25 – $15.00/sq. ft. 20 to 30 years
TPO/EPDM $7.50 – $9.50/sq. ft. $8.25 – $10.45/sq. ft. 25 to 30 years
Tar & Gravel $9.45 – $10.50/sq. ft. $10.45 – $11.55/sq. ft. 15 to 30 years

 

Replacing a flat on a residential building usually averages around $12,000 and $20,000, whereas replacing a flat roof on a commercial building can easily run upward of $100,000 – all depending on the surface area. Take a look at our roofing cost article for more details. 

Which flat roof material to choose…

Best value for money: TPO, as it’s similar to EPDM, yet costs a little less

Most eco-friendly: EPDM as it is entirely recyclable

The coolest: a green roof with a terrace

Would you like to know the cost of a roofing project?

Why you need a qualified roofer for your flat roof

According to one of our 360° Verification Coordinators, “choosing the contractor is more important than picking out the roofing material. Each material has its set of qualities, however, that isn’t always the case when it comes to roofers. Most clients end up calling us after having issues with their poorly installed roofs that have hurt more than the roofing’s cost.” To get up to 3 quotes from the best roofers in town, Call us or fill out our form & a Renovation Advisor will gladly help you out! Our services are at no cost, no obligation to you! 

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