Roofing 101: Which Membrane Option Is Right For You?

Many people think that all roofs are made with basically the same materials, but this could not be further from reality.  There are actually many different kinds of roofing membranes, each catering to different roof types in order to protect them best. Like all construction elements, each roofing membrane has its pros and cons, and the key is to make sure you are choosing a roofing material that fits your needs. That’s why we’ve put together a comprehensive list of the top five main roofing membranes, and the most important things you should consider before making a decision for your roof.

1. Four or Five Ply BUR

4 ply built up asphalt and gravel roofing replacement

A 4-ply roofing system consists of roof felts that are composed of four or five layers of reinforcement, hence their name. Each ply is embedded in a full mopping of asphalt bitumen. These materials provide both an adhesive and waterproofing membrane, while the 4-plies of felts are meant to provide reinforcement to the surface. The stone ballast provides an excellent weathering surface and protection from the ultraviolet (“UV”) rays of the sun.

This Roofing Membrane Is Great For:

  • Building owners who want reliability: 4 & 5 ply BUR roof membranes have been used continuously for over 175 years, making this system one of the most reliable statistically.
  • Peace of mind: The multi-ply redundancy is a safety factor and major advantage with this type of roofing membrane.  Damage to the interior requires a penetration through multiple plies of membrane.
  • Buildings that are in areas with lots of wind: the 4 & 5 ply BUR roof membranes are extremely wind resistant and perform better under such conditions.
  • Insurance: This type of membrane yields a Class A fire rating requirement, which could mean savings on your building insurance.

You Should Reconsider If:

  • Odour is a big concern: Even though this kind of roofing membrane can be installed in a low-odour application, there is still the potential for some odour at ground level at the source of the bitumen if temperature is not tightly controlled. There is a workaround but it is best if expectations are established prior to project commencement.
  • If your building is in a densely wooded area: Issues with roof top collections of algae, organic debris and dirt are most common with a ballasted system, because the gravel can trap dirt. The presence of ponding water makes this issue more problematic, but if you commit to routine maintenance with your roofing system, these problems can be easily avoided.

2. 3-PLY Hybrid BUR

Hybrid BUR membranes are made by mopping together modified bitumen membrane and traditional glass fibre felt paper with hot asphalt. 3 ply hybrid systems create a watertight seam that can handle high and low temperatures beautifully.

This Roofing Membrane Is Great For:

  • Peace of mind: The multi-ply redundancy is a safety factor and major advantage with this type of roofing membrane.  Damage to the interior requires a penetration through multiple plies of membrane.
  • If fire is a concern: Use of aggregate cover (pea gravel) yields a Class A fire rated assembly which exceeds building code requirement for Class C – this could bring some insurance savings to building owners.
  • If time is of the essence: These systems marry 1 ply SBS base sheet with 2 plies of glass felt to enhance performance allow for quicker installation times.

You Should Reconsider If:

  • If your building is in a densely wooded area: The ballast (gravel) of the 3 ply hybrid system can trap vegetation if not routinely maintained. If you have this kind of roofing membrane ( or any roofing membrane for that matter), you should have routine scheduled maintenance in order to avoid issues in the future.
  • If your building is in direct sunlight most of the time: Like the 4 & 5 ply, prolonged exposure to UV rays can degrade the quality of the roof membrane over time due to its darker colour. If temperature is a main concern, this may not be the right membrane for your structure.

3. 2 ply SBS Modified Bitumen

2-ply SBS (Styrene Butadiene Styrene) modified bitumen membranes are pre-fabricated membranes that are reinforced with mats consisting of polyester, fibreglass, or a combination of materials. These membranes are available in a variety of thicknesses and work well in harsh weather conditions. This membrane is easy to maintain due to its smooth surface.

This Roofing Membrane Is Great For:

  • Problematic installations: There are various hot and cold installation methods available allowing for great flexibility depending on project constraints.
  • Buildings that have concerns with punctures: The 2-plies of roofing are approximately 8mm thick, allowing for a high level of puncture resistance compared to other membranes.
  •  Buildings in direct sunlight: White membrane options are available to meet “cool roof” designations, where needed, with a slight incremental cost. A cool roof can lessen a building’s energy consumption, especially during summ

You Should Reconsider If:

  • It’s the middle of winter, and you need a roof right away: These membranes require special cold weather application techniques during the winter months, so if repairs or replacement are urgent, then this isn’t the right membrane for your needs. If you are set on this kind of material, it needs to be installed expertly during the winter months or in usual methods of application during the rest of the year.
  • You have concerns about workmanship: Seam failure can result from improper installation techniques that lead to seam voids or bad welds. If you are going with this membrane, make sure you are using a reputable company that has worked with this material in the past and is warranty certified with the membrane manufacturer.

4. 1 ply PVC/TPO/EPDM

PVC membranes are a hard plastic roofing membrane that can withstand pressure from the elements and heavy use.

This Roofing Membrane Is Great For:

  • Buildings where building codes mandate cool roof designations: White membrane options can often meet “cool roof” designations, where needed, with no incremental cost. A cool roof can lessen a building’s energy consumption, especially during summer months.  The roofs need to be thoroughly cleaned regularly to maintain the cool roof solar reflectivity rating.
  • Owners who do not want any open flame use on their project: No flame or torch at all – installation is done with adhesive and/or screws & plates (mechanical fasteners) and seams are hot air welded – but no flame. The installation can be done using low VOC adhesives and/or screws/plates together with hot air welding to meet safety concerns.

You Should Reconsider If:

  • Your structure has a lot of equipment on it: Single ply membranes are susceptible to punctures especially where there is extensive roof traffic or HVAC equipment. Vibrations from mechanical equipment can cause mechanical fasteners to back out, puncturing the membrane.
  • You have routine traffic on your roof: This membrane is extremely slippery when wet, or icy and can be a huge hazard to your employees/service technicians if they frequent the roof, especially in the winter.  Walkways are problematic as the sub-trades rarely use them as intended and they often create ponding water and potential blow-off issues.
  • You have concerns about wind: Single-ply roofing is prone to damage from wind uplift. If the wind conditions are severe enough or if the membrane attachment method is deficient, a strong wind can tear off some or all of the roof membrane.

5. Inverted Roof Membrane Assembly “IRMA” or Protected Roof Membrane Assembly “PRMA”

An inverted roof refers to a flat roof where the waterproofing layer is underneath the thermal insulation as opposed to above it. Inverted roofs use insulation that can resist water absorption, which provides excellent thermal performance, and can reduce condensation.

This Roofing Membrane Is Great For:

  • Buildings that have UV damage concerns : These systems can withstand surface traffic and remain protected from UV rays of the sun and mechanical damage.
  • Building owners who want to make an investment: While inverted roofing systems are typically more costly, they last longer than traditional built-up roof systems. IRMA roofs are designed to have up to a 40-year life cycle. This assembly has excellent life-cycle costing. Initial up-front construction costs account for only 5 to 10 per cent of the building’s cost over its service lifetime; operating and maintenance costs account for 60 to 80 per cent.
  • If your building is a high-rise: Inverted roofs are worthy of consideration for high rise projects because they protect the membrane from damage due to restoration projects including outrigger beams for swing stages and lifelines on roof anchors.

You Should Reconsider If:

  • Cold weather is a main concern: There are cold weather challenges to displace ballast to locate and repair leaks. When the ballast is frozen repairs become very complicated to execute properly.
  • You have had issues with ponding water in the past: Some older inverted roof systems exhibit maintenance issues brought on by ponding water and displaced ballast. Ponding water lifts the insulation due to its buoyancy which in turn displaces ballast and can lead to insulation blow off risks. However, effective positive drainage can usually help to assuage the issues that come with inverted roofing systems and ponding water.

There are many pros and cons to each type of roofing system available for your structure. Each comes with its own list of challenges and benefits, which is why at Elite Roofing, we work with building owners, architects, and developers in order to assure that their building needs are being met. If you don’t see the membrane that you were looking for, or if you have questions regarding any of these, feel free to contact us, we’re here to help you get the Elite Advantage.