Flat Roof vs Pitched Roof: The Pros and Cons - United Roofing Inc

Flat Roof vs Pitched Roof: The Pros and Cons

When designing commercial buildings around Calgary, Edmonton, and Vancouver, one of the most basic decisions to make is whether to opt for a flat roof or a pitched roof.

There are pros and cons of both types of roofs and, while commercial flat roofs are more common, you will see plenty of examples of both if you drive around these cities.

Whether you are looking to design a roof for a retail building, office/office tower, condominium/apartment building or another commercial/industrial building, it’s important to make an informed choice.

So, how do flat and pitched roofs compare in terms of structure, installation, maintenance, durability, suitability for our climate, and cost?

To help you decide on a suitable roof for your project, we take a look at the pros and cons of flat roofs and pitched roofs below.

What is a commercial flat roof?

You may expect flat roofs to have no slope but this is not always entirely true. Most commercial flat roofs appear flat to the naked eye but do, in fact, slope very gradually as it is easier for drainage. They may have a “pitch” of up to 12 degrees.

Flat roofs are surprisingly varied in design and there are multiple options with materials depending on needs and preferences.

A few of the most common types of flat roofs you will see in Calgary, Edmonton, and Vancouver are:

  • Built-up roofs
  • Modified bitumen roofs
  • PVC roofs
  • EPDM, TPO or SBS membrane roofs
  • Metal roofs

You might even see flat roofs on some very modern residential buildings or used for sustainable, green roofing systems (vegetative rooftop systems), which has become a popular choice for commercial buildings in some cities.

So, what are the pro and cons of flat roofs?

Flat roof pros

Being practically flat has its advantages. Most obviously, flat roofs are easy to access and walk on, which can make installation and maintenance easier. A roof that is easier to inspect up close, like most flat roofs, makes problems easier to identify.

Unseen problems are a real problem for roofs in general. Sometimes, a problem exists for months before heavy rains or snowfall start to expose the weaknesses – and this often results in expensive repairs or even roof replacement.

A flat roof is accessible for simple maintenance like cleaning out gutters, removing pooling water, and so on. So, it is easy to maintain and can help early diagnosis of problems, which prevents costly fixes.

Most flat roofs are affordable as well as practical. Fewer materials may be required, and the structure is usually a lot simpler than a pitched roof.

You also have the option of several different materials/designs to suit your budget. Because installation is easier and quicker, this also helps to keep the upfront costs of flat roofs more manageable.

Flat roofs generally offer good protection from the Alberta and BC climates and stand up well to high winds. There are also plenty of fire-resistant options available.


Flat roof cons

Because of the variety of materials used for flat roofs, it’s a little difficult to generalize the pros and cons.

Depending on the material, some flat roofs develop cracks more easily than pitched roofs. Cracks mean leaks – not good for any roof.

Some flat roof materials/membranes are sensitive to temperature fluctuations, which can be extensive in Calgary and Edmonton especially, so cracking can be a problem unless spotted early and fixed.

The other main drawback with flat roofs is potential difficulties with drainage. Though they do offer a slight slope, the runoff of water is much easier on a sloped roof where gravity helps. Heavy rain can cause water to pool, potentially leading to leaks.

In areas of high snowfall, snow can build up more easily on flat roofs too, creating other challenges with the weight of the snow and drainage after it melts. Flat roofs require a waterproof seal, which must be maintained regularly to prevent leaks and costly repairs.

You might read in some places that flat roofs have a shorter lifespan than pitched roofs. This is not necessarily true. Some well-maintained metal flat roofs can last 50 or 60 years, and modified bitumen, built-up or membrane-based roofs can last 30-45 years with proper maintenance and care.

What is a pitched roof?

Pitched roofs come in a variety of styles but they all have one common feature: they have a visible “peak” and a slope, creating a triangular appearance.

Gable, cross gable and hipped designs are all commonly used in pitched roofs, the main difference being the angle of the slope.

Most commonly, you see pitched roofs on residential homes in Calgary, Edmonton and Vancouver. They form a tall attic at the top of the home that can be put to good use as a storage space or a bedroom. However, pitched roofs can also feature on some commercial buildings.

Pitched roof pros

A major advantage of sloped roofs is that they have a natural drainage system, allowing gravity to look after the flow of water down from the roof to the gutter system. With heavy rains, property owners with sloped roofs have few worries about water pooling on the roof.

Also, compared with flat roofs, there is less chance of snow build-up during times of heavy snowfall, as it usually slides off relatively easily when it starts to melt.

For commercial buildings, aesthetics is often less of a factor for building owners than it is for residential property owners. Practical considerations normally come first, so the more “homely” appearance of sloped roofs is usually not a deciding factor for commercial building projects.

Depending on the material you choose for your pitched roof, you can expect a lifespan of 20 to 50 years –similar to flat roofs.

Ass discussed below, all roofs require regular maintenance, but some consider the maintenance requirements of pitched roofs to be lower than with flat roofs due to the reduced chance of water and debris building up.

Pitched roof cons

Because of their sloped and peaked design, a larger support structure is required for pitched roofs.

Additional materials and specialist expertise may be required, so a significant disadvantage of pitched roofs is an increased installation time and potentially higher upfront costs. Generally speaking, therefore, pitched roofs are more expensive than flat roofs.

Also, repairs and maintenance of the roof are more challenging than flat roofs because of the dangers of working on a slope. Whereas a building owner can usually inspect a flat roof easily by walking around on it, this is much more challenging with a pitched roof.

Finally, in times of high wind, a sloped roof may have a higher potential exposure to damage than a flat roof, all other things being equal.

Choosing the right roof for your commercial building

Commercial buildings have different priorities from residential ones. While cost and durability are essential to both, aesthetics generally become less critical for commercial building projects, and practicalities such as safety and maintenance requirements are the primary considerations.

Bear in mind that the climate in Calgary and Edmonton is different from that of Vancouver. The colder temperatures and heavier snowfall are all issues to consider before installing a roof in Alberta.

Generally speaking, for commercial buildings all over Canada, flat roofs are the go-to design. They are cost-effective, durable, safe and practical for most retail buildings, office towers, condominiums and apartment buildings, and other commercial and industrial buildings.

Maintain your roof for extra longevity

The secret to extending the life of your roof is regular maintenance.

This applies to almost any roof because problems can be flagged early and fixed well before a roof replacement becomes necessary.

A flat roof should be inspected professionally at least once a year, if not more regularly. They are susceptible to water pooling after heavy rain or snow, and standing water on a roof is never a healthy sign.

Because of their accessibility, most flat roofs are relatively easy to inspect by walking around with a detailed checklist. Try to inspect your roof regularly in between the annual professional maintenance checks.

You can also extend the life of your roof by getting the right professional advice before you decide on design and materials and by ensuring that you install it with a reputable company.

Need more information about flat roofs vs pitched roofs in Calgary or Edmonton? Book a free consultation with us.