showing a flat roof

Best Roofing Systems for Flat Roofs

Because flat and low-slope roofs collect moisture easily, they need to be built differently than other types of roofs. For example, shingles cannot be used for this type of roof. They are too vulnerable to leaks and instead you need a seamless protective covering.
Choosing the best type of roofing system for a flat roof is a challenge for many homeowners and businesses owners. There are multiple types of roofing systems that will work for flat roofs, and when deciding on the right one, there are multiple factors to take into consideration. These factors include: durability, the building’s structure and roof weight limitations and the cost. Listed below are common flat roof systems, including their pros and cons. The characteristics of each roofing system should be reviewed carefully as you try to choose what is the best roofing system for a flat roof?
Asphalt and gravel have long been the standard for flat roofs. However, in the past 20 years or so, elastomeric bitumen coatings which use a two-layer system have become popular because of their sturdiness and now make up a large portion of the residential market.

Asphalt and gravel System

An asphalt-and-gravel roof membrane consists of several overlapping layers of roofing material, three of which are laminated together using molten asphalt. Roofing felt is then used to smooth out uneven areas of the roof decking and form a stable base for the asphalt, which prevents water from seeping through.
A layer of gravel is then added on top of the membrane to shield it from the sun’s UV radiation. Without that protection, the asphalt will deteriorate quickly.
If you choose this type of coating, be aware that installing it is difficult. The roofers will be handling molten asphalt and working with a noisy machine called a tar kettle. There will most likely be unpleasant odours and toxic fumes to be careful of as well.
It’s well known that flat and low-slope roof structures have specific needs. For example, shingles are never used for this type of roof: they are vulnerable to leaks, so they require a seamless protective covering however, its lifespan can be maximized by simple seasonal maintenance, which consists of adding gravel over any bare spots. An asphalt-and-gravel roof covering should last for 20 to 25 years, depending on the quality of the installation job and of seasonal maintenance.

Elastomeric bitumen:

Elastomeric membranes come in rolls and are used to create roof coverings typically made up of two layers – a bottom membrane and a granule-covered top sheet. The granules make the covering resistant to weather, tears, and UV radiation.
The top sheet is welded using a torch. Installation of an elastomeric membrane is much neater than laying an asphalt-and-gravel system. However, working with an open flame means a fire risk so if you choose this method, make sure your roofer has the right kind of insurance.
Some types of dual-layer elastomeric membrane can also be cold-applied. In this case the strips of each layer are self-adhesive, and all the installer has to do is remove a film covering the adhesive as the strips are unrolled. This product is also a good substitute for shingles on a low-sloping roof that lacks a drain to collect rainwater.
An elastomeric membrane results in a lighter coating with greater impact resistance than the classic method, due to its elasticity—an advantage that is even more apparent in cold weather. This type of roof covering is also easier to inspect and repair, as there is no layer of gravel masking the surface.
The cost of a hot-applied elastomeric membrane is 10 to 15% higher than for asphalt-and-gravel coating. It lasts much longer, however: an average of 30 to 35 years.

Synthetic coverings

Synthetic coverings like polyvinyl chloride and thermoplastic polyolefin and ethylene propylene diene monomer are single layer membrane system. The roofer uses scissors to work around obstacles like vents and chimneys. Because of how they are applied, synthetic coverings are best used for large areas, free of obstacles.
Typically synthetic membranes are either mechanically applied or welded using a tool much like a hair dryer to soften the membrane.
Single-ply synthetic membranes, also known as monocouche coverings in Quebec are light, recyclable, can be installed quickly, and cost 10 to 15% less than asphalt-and-gravel coatings. They are also easy to maintain and repair—except during the winter months when hot-air gluing methods are less effective.
PVC roofing system is highly reflective and very durable. PVC is one of the top flat roof options because it is easy to install and lacks water permeability, meaning it can resist water ponding. It’s three main benefits are very comparable to number 5 on the list, spray-applied roof coatings. The problem with PVC, and the biggest difference from roof coatings, is that it is applied in rolls, and therefore it has seams that can lead to roof failure. When it is rolled out, these seams must be taped or glued together. While this may resist water for a while, it will not hold up for 10-15 years as a seamless roofing system would.
Ethylene propylene is a rubber compound rather than plastic. They are very durable and have built a reputation around durability, but they are not without their weak points. The seams in the EPDM system are treated with adhesives and this makes the seams vulnerable over long periods of time. This sealing system often leads to maintenance on the seams, or building owners living with leaks. This is one of the more maintenance-intensive flat roof options.

Is it a good idea to cover over an existing coating?

It is possible to cover an asphalt-and-gravel coating with a single-ply membrane, after first removing the gravel and laying down sheets of high-density fiberboard. Many roofers warn against doing this, however, because humidity rising from the home can be trapped in the old coating, between the framing and the new membrane, warping and damaging the roofing system. For more dependable results, it’s best to start from scratch.

Finding the Right Roofing Systems for Your Flat Roof

Can’t decide on the best flat roofing system for you? Schedule a free consultation with Cambie Roofing. We are experienced roofers who will be able to weigh all your considerations and recommend a roofing system that will work best for your Vancouver home or business.

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Types of Roofing Materials

As a homeowner, you may not think much about your roof, but it is one of the most important aspects of your home and should be well-maintained. Having the right roof not only adds value to your come but communicates your style to everybody who passes by. While roof framing, preparation and proper installation are always important, the material you choose for your roof really is the most important decision when it comes to a new roof.

Asphalt Shingles

This is one of the most popular roofs in Vancouver as they are durable, relatively inexpensive and are waterproof, a very important aspect in the city’s climate. They come in a wide variety of colours and styles and are easy to install. They are also suitable for a wide range of temperatures.
Asphalt shingle roofs should last between 20 and 50 years on average, providing that you properly maintain them and get a professional to check them twice a year. Another fact to consider is that temperature extremes effect the lifetime of the roof and although Vancouver’s temperature stays relatively consistent, it’s something to be aware of.
Disadvantages of asphalt shingles include a shorter life than many heavier tiles, especially if they are walked on. Dark asphalt shingles are prone to fading and tend to exhibit inconsistencies in color. The black marks are caused by algae, which doesn’t survive well in direct sunlight. Homeowners can get rid discoloration by applying a sodium hypochlorite bleach solution and rinsing it off fresh water. Homeowners can also look for an algae-resistant shingle such as 3M’s Algae Block, which contains copper granules that can help prevent new growth.

Wood Shake and Cedar Shingles

This is another popular choice for Vancouverites. They can be manufactured from recycled wood which are a green-friendly choice, producing minimal impact on the environment and on the quality of water runoff. They usually last around 30 years or more, making them a solid investment in environmental responsibility for homeowners.

Slate and Title Roof Shingles

Slate and Tile Roof give your home a natural appearance. Although more expensive than asphalt, they are great for a classical, upscale home. Slate and Tile are resistant to rot and fire so you don’t need to worry about upkeep as much. They are available in a variety of colours and styles.
Disadvantages of slate and tiles are their weight and cost, and the high degree of expertise needed for installation. Slate tiles are easily broken underfoot, complicating gutter cleaning and rooftop maintenance.

Ceramic Roofs

Ceramic Tiles give a house character and are generally durable. Advances in the manufacturing process make the tiles resistant to fading. Ceramic tiles are fireproof, and quality tiles should last 50 to 70 years.
The problem with ceramic roofing tiles include their unsuitability for climates with fluctuating weather. Ceramic tiles are prone to erosion under these conditions. While the tiles are durable, they are also fragile. High winds can damage them, as will walking on the tiles.

Clay and Concrete Tiles

Clay and concrete tiles are not very popular in Vancouver. They add texture and elegance to a roof. Genuine flat, ribbed or scalloped clay tiles are extremely durable but also very heavy, and must be installed by a professional. Concrete tiles are versatile and are less expensive than genuine clay, but also have a heavy weight.

Metal roofing

Again metal roofs not very common in Vancouver. However, they are becoming increasingly viable, as metal shingles are low maintenance, lightweight and more environmentally friendly. However, installation can be tricky and requires a contractor with experience installing a metal roof.
As a metal roof starts to lose its shine, repainting is an option as long as the roof’s structural integrity is in good shape. It usually costs less to repaint a metal roof than to replace it.

Flat roof

Flat roofs can require a great deal of maintenance. As the homeowner, you are responsible for ensuring it stays watertight. The roof must be cleaned regularly to prevent leaves and debris from clogging the drain. Also, the sun will gradually cause the roof to degrade, as flat roofs located in environments where the temperature can go from hot to cold in a short period of time are more vulnerable to damage.
Flat roofs are typically less expensive to install than sloped roofs. They may provide a safer option, as there is less chance of falling off when you are on top of a flat roof. They are usually easy to access and can allow you to achieve a certain visual appearance.

Torch On Roofs

Torch On Roofing consists of two or more layers of modified asphalt that are usually melted together by a torch. This creates a roof that is resistant to ultraviolet light and a waterproof barrier.
The Torch On Roofing is usually used for flat roofs where snow or rain can easily collect and sit for long periods of time. It covers the entire roof at an even thickness, usually about 3-4 mm thick, while traditional tar roofs can have bumps, thinner, and thicker spots.
The downside to a Torch On Roof is installation can be hazardous. It’s very easy to make a mistake while applying torch down materials to a roof. Materials can be accidentally overheated and cause a fire that can quickly spread throughout the dry, hot attic area.
The material used in applying a flat roof is technically known as ‘Bitumen’, but more commonly known as asphalt. Bitumen by itself is perfect for roofing, as it has good water proofing qualities; however, Torch applied roofing needs to have something added to it to stabilize its inability to expand and contract.

What type of Roofing is Right for me?

When choosing roofing materials there are many things to consider. Does the material offer good performance in different weather conditions? Although Vancouver stays mild, it can occasionally get up to 30 degrees Celsius or dip below freezing. You need a roof that can withstand these temperature extremes.
You also need to consider the cost, maintenance, and life span of the roof. Some roofs are cheaper to install but cost more to maintenance while others vice versa.
Lastly, you should think of the best style for your house and the surrounding neighbourhood. The last thing you want to do is to install a roof that sticks out like a sore thumb.
So call 604-261-1111 and ask the experts a question.