The Field Guide to Commercial Roofing Membranes
Updated: 6 days ago
TPO, PVC, EPDM, SBS, APP, BUR, PMMA. Sometimes commercial roofing can feel a little like alphabet soup.
Unless you work with these systems every day, the differences aren't always obvious. The way they're engineered, how they're installed, and where they perform best can vary quite a bit from one system to another.
While this guide won't instantly make you a roofing expert, it can help you understand what differentiates each system so you can figure out which one makes sense where.
Let's break them down.
Single-Ply Roofing
We'll start with TPO, PVC, and EPDM. All three use a single layer of membrane (or ply) as the primary waterproofing layer. TPO and PVC are thermoplastics with heat-welded seams, whereas EPDM is a synthetic rubber (so it behaves a little differently).
TPO
Economical and versatile
High reflectivity
Great for high temperature areas
Economical and relatively quick to install
Great for: Big box stores, retail, offices, and a wide range of commercial roofs.
If you've spent any time around commercial roofing lately, you've probably seen plenty of TPO. It's the most widely used commercial roofing membrane in the country, and it's versatility has a lot to do with that.
TPO is a reflective thermoplastic membrane with heat-welded seams. It's economical, relatively quick to install, and works for a wide range of commercial buildings. Johns Manville reinforces its TPO with polyester fabric and uses a UV-resistant formulation for flexibility and weldability.
For a straightforward commercial roof without unusual exposure or detailing requirements, TPO is often one of the first systems we consider.
PVC
The go-to for chemical exposure
Resistant to oils, grease, chemicals, and industrial pollutants
More flexible than TPO (added plasticizers make it more pliable)
Wider welding-temperature window makes flashing easier
Great for: Restaurants, food-processing facilities, airports, industrial buildings and other roofs where chemical exposure is a concern.
At first glance, PVC looks a lot like TPO. They're both thermoplastic membranes, both can provide a reflective roof surface, and both have heat-welded seams.
The big difference lies with PVC's chemical resistance. Grease, oils and certain chemicals can be tough on roofing membranes, but PVC is engineered to handle that kind of exposure better. This is why you'll often see it on restaurants, processing plants, airports and industrial buildings.
PVC is also more pliable than TPO, and its wider welding-temperature window can make flashing easier for the installer.
EPDM
Flexible rubber roofing
Good resistance to cold weather
Fast installation
Known for flexibility and long-term durability
Great for: Northern climates, ballasted roof assemblies, warehouses and projects where flexibility and proven performance are priorities.
EPDM is an entirely different animal. Instead of a thermoplastic, it's a thermoset (or synthetic rubber) membrane. It's flexible, durable and has been used on commercial roofs for decades.
It stays flexible in cold temperatures and can be manufactured in large sheets, which means fewer field seams across a big open roof. (Think warehouses and similar buildings with a lot of roof area. The large sheets can cover quite a bit of ground.)
JM does something a little different with its EPDM, too. Its sheets are extruded rather than traditionally calendered, which produces a thicker, more uniform membrane that requires less prep during installation.
One thing to keep in mind: EPDM and oils don't mix. EPDM can swell and absorb oils, so it's not the membrane we'd look at first for roofs where grease or oils are present.
Modified Bitumen Roofing
Now we're moving out of single-ply roofing and into our multi-ply systems, which typically use two (and sometimes three) plies. The additional layers provide built-in redundancy, so if the top layer is damaged, there's still another membrane layer beneath it.
SBS and APP are both asphalt-based membranes used in multi-ply roofing systems. What sets them apart is how the asphalt is modified, which ultimately changes how each membrane behaves.
SBS
Flexible and highly customizable
Good flexibility and elasticity, even in colder temperatures
Five different application methods available
Excellent performance in high wind and storm areas
Great for: Schools, government buildings, high-traffic roofs and projects where durability, redundancy and system flexibility are important. It's also very popular here in NYC.
SBS is asphalt modified with a rubber-like polymer. That gives the membrane more elasticity and helps it stay flexible as temperatures drop.
One advantage of JM SBS is just how many ways you can build the roof. Johns Manville offers five installation methods: cold-applied, heat-welded, self-adhered, mechanically fastened and hot-applied. You can also choose from fiberglass, polyester and composite reinforcement options.
That gives you a lot of flexibility in how your roof is designed and installed.
APP
Tough and economical
Higher tear strength
Strong weatherability
Can match asphalt shingle colors
Great for: High temperature areas and commercial roofs where strength and weatherability are priorities.
The big difference between APP and SBS is the modifier. Instead of the rubber-like polymer used in SBS, APP uses a plastic polymer that gives APP particularly strong high-temperature stability. (JM's asphalt formulation remains stable above 300°F.)
JM offers fiberglass, polyester and composite reinforcement options, with polyester-reinforced membranes providing higher tear strength than fiberglass-reinforced membranes.
And while APP is commonly torch-applied (heat-welded), JM also offers APP membranes that can be cold-applied.
Built-Up Roofing
Johns Manville has some history with this one. They pioneered built-up roofing in America more than 160 years ago.
BUR
Built-in redundancy
Alternating layers of bitumen and reinforcing felts
Multiple waterproofing layers provide built-in redundancy
Exceptional resistance to water and weather
Great for: Commercial roofs where long-term durability, weather resistance, and multi-ply redundancy are priorities.
Johns Manville's history with built-up roofing goes all the way back to 1858. That's when 21-year-old Henry Ward Johns was working out of the basement of his New York City tenement, using his wife's clothes wringer and a tea kettle to apply hot tar to cloth and make roofing material.
Today, JM still makes built-up roofing. The basic idea hasn't changed all that much either. Layers of reinforcing felt alternate with layers of bitumen to build the waterproofing system on the roof. If one layer fails, there are others behind it. That built-in redundancy is one of the reasons BUR has stuck around for so long.
Liquid-Applied Roofing
So far, every system we've covered uses a roll of membrane. Liquid-applied roofing works a little differently. The resin is applied with reinforcement and cures to form a waterproofing membrane in place. That makes it useful for roofs with complex details or areas where cutting and fitting sheet membranes can get complicated.
PMMA
Seam-free waterproofing
Good for roofs with lots of penetrations or irregular shapes
Can be used for roofing or flashing
Resistant to chemicals, UV, ponding water, and root penetration
Great for: Plaza decks, garden roofs, roofs with lots of penetrations and small or irregular-shaped roofs.
PMMA is a fast-curing resin system that cures into a reinforced waterproofing membrane without traditional seams.
It's a good option when there are a lot of details to work around (curbs, drains, pipes, equipment, transitions, and odd shapes). With a sheet membrane, that often means a lot of cutting, fitting, and flashing, but a liquid-applied membrane conforms to those areas.
That's why PMMA makes a lot of sense for smaller or irregular roofs and roofs with a lot of penetrations. It's also commonly used on plaza decks and garden roofs, and can be used as flashing on bituminous roofing systems.
The Commercial Roofing Cheat Sheet
System | Type | Consider it when |
TPO | Single-ply | You want an economical, reflective roof for a wide range of applications |
PVC | Single-ply | Oils, grease, or chemical exposure are a concern |
EPDM | Single-ply | You want cold-weather flexibility and long-term durability |
SBS | Modified bitumen | You want a flexible multi-ply system with plenty of installation options |
APP | Modified bitumen | High-temperature stability and weatherability are priorities |
BUR | Built-up roofing | You want a traditional multi-ply system with plenty of built-in redundancy |
PMMA | Liquid-applied | The roof has a lot of penetrations, transitions, or irregular geometry |
One note before we wrap up: selecting a membrane isn't the same as designing a roof. The membrane is just one part of the roofing system. Insulation, cover boards, attachment methods, vapor barriers, performance requirements, and deck type all play a role in how the roof comes together. Understanding the basic differences between the membrane types just gives you a good place to start.
Need help deciding?
If you're working through a spec or trying to figure out which system makes sense for your building, give us a call. We do this every day.
