Bitumen is a black, sticky, and viscous material that is derived from crude oil and is often used in roofing applications due to its weatherproofing and waterproofing properties. This roofing method is very popular, especially for flat roofs and low-sloped roofs.
However, what some people don’t know is that there are different kinds of modified bitumen, with two main kinds being APP and SBS. Right now, we will compare the two in order to see which one is better for your needs.
What Is APP?
APP bitumen is also known as atactic polypropylene-modified bitumen. This is a very special type of modified bitumen that is used in many roofing applications. The defining feature here is that it has atactic polypropylene, which is a synthetic polymer, added to it.
This is a special modification that helps to enhance various characteristics of the bitumen, mainly by making it more resistant to temperature changes, more durable, and more flexible.
The addition of this polymer also helps to improve the UV radiation resistance of the bitumen, which therefore makes it more suitable for roofing applications that are exposed. Various roofing membranes that are made with this type of bitumen are often used in roofing systems, most often in modified bitumen and built-up systems.
There are two main types of APP bitumen roofing membranes available, with the first being modified bitumen sheets, which are reinforced roofing membranes that have a fiberglass or polyester mat embedded in them for extra stability and strength.
These sheets are usually available in various thicknesses and sizes, and can often be cold-applied, self-adhered, or torch-applied, depending on the product in question.
The other type is the APP-modified bitumen role, which is generally used for flat roofs and low-slope roofing systems. These are overlapped to create continuous and seamless roofing surfaces. Some of the biggest advantages of this type of bitumen include great elongation and flexibility, fantastic UV resistance, great weatherproofing and waterproofing capabilities, and relative ease of installation.
What Is SBS?
We then have SBS bitumen, which is also known as styrene-butadiene styrene-modified bitumen. This is a special type of modified bitumen that is often used in waterproofing and roofing applications. It is similar to APP, but it involves adding a different synthetic polymer to the bitumen to improve various performance aspects.
Styrene butadiene styrene is a synthetic rubber polymer that is combined with bitumen to create what we know as SBS-modified bitumen. The addition of this special polymer produces additional benefits that regular modified bitumen on its own does not have.
One of the biggest benefits is that this type of roof is extremely flexible, which allows it to deform and stretch without cracking or breaking. This is great for areas that have extreme temperature fluctuations. This type of roofing also sees enhanced durability and features excellent resistance to rays, weather, aging, and more.
Furthermore, it also performs very well in low temperatures. Additionally, it has superior waterproofing when compared to many other types, not to mention that it has great adhesion with various types of roofs as well.
APP vs. SBS: What Are the Differences?
Now that we know what both APP and SBS are, let’s figure out what makes them different from each other.
One of the biggest differences between these two types of bitumen is of course that one has a tactic polypropylene added to it, whereas the other has styrene butadiene styrene added to it. The basic ingredients are simply different.
Another big difference to consider here is that APP performs decently at moderate temperatures, but it can become brittle at lower temperatures, which can lead to cracking. SBS bitumen, on the other hand, performs very well in extreme cold, and will not crack even when it freezes.
APP bitumen is relatively flexible, but not quite as flexible as its SBS counterpart. APP bitumen can handle some temperature fluctuations and remain somewhat flexible, but it just doesn’t perform as well on this front as SBS-modified bitumen, which has excellent elongation and flexibility properties no matter the temperature.
Something else to consider is that SBS-modified bitumen has some of the best UV resistance around, which makes it ideal for exposed roofing applications. APP bitumen on the other hand has decent UV resistance, but not quite as good as SBS, especially when it comes to prolonged exposure to high levels of sunlight.
Furthermore, SBS bitumen tends to be serviceable in a temperature range of between -20 degrees Fahrenheit to 270 degrees Fahrenheit, whereas APP bitumen is serviceable between 15 degrees and 300 degrees Fahrenheit.
This means that SBS bitumen can be much more easily worked with in lower temperatures. With that being said, SBS bitumen also has a lower softening point, just 230 degrees, whereas the softening point of APP bitumen is 245 degrees.
For a variety of reasons, SBS-modified bitumen roofing is often a bit less forgiving and harder to install than APP.
APP vs. SBS: Which One To Use?
Which one of these two types of roofing you use depends on a variety of factors such as climate, building location, budget, and project requirements.
Generally speaking, SBS-modified bitumen is better for areas that have extremely cold temperatures and temperature variations, Whereas APP is usually better for warmer climates.
You should now know exactly what both APP and SBS modified bitumen roofing are, what both of their pros and cons are, what makes them different, and which one is best suited for your next project.