Modified Bitumen Roofing: What It Is, Types, Pros & Cons

Modified Bitumen Roofing: What It Is, Types, Pros & Cons

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When it comes to flat roofs and low-slope roofs, modified bitumen roofing is by far one of the most popular and common types of roofing to consider. However, many people might not know what it is, what the different types are, or what its pros and cons are either.

This is exactly what we are here to cover today.

What Is Modified Bitumen Roofing?

Modified bitumen roofing is a specific type of roofing or roofing material that is often used for both residential and commercial buildings. This is an evolution or advancement of traditional asphalt roofing, which combines asphalt and various other materials to provide enhanced performance and beneficial properties for roofs.

Modified bitumen roofing is most often used for flat roofs and low-sloped roofs, as it is known for its great flexibility, weather resistance, and durability. There are two main components of modified bitumen roofing, which are the asphalt and the modifier.

The base material used for modified bitumen roofing is usually asphalt, which is a highly viscous, black, and sticky substance that is made from crude oil. The modifier is usually something like atactic polypropylene or styrene butadiene styrene, which are specific types of polymers that help to improve the performance of the modified bitumen.

The type of modifier used determines what type of modified bitumen roofing is being used. Modified bitumen roofing is also usually installed using multiple layers, and there are various application methods.

It can be applied using a cold-applied adhesive system, a hot-mopped system, and a torch-applied system. To ensure maximum longevity and durability, proper installation is required. Because of its ease of installation, durability, and overall performance, modified bitumen roofing is often a very popular choice for flat and low-sloped roofing applications.

2 Types of Modified Bitumen Roofing

There are two main types of modified bitumen roofing to consider, and these include SBS-modified bitumen and APP-modified bitumen.

First, we have SBS-modified bitumen, which stands for styrene butadiene styrene, a type of synthetic rubber. Modified bitumen roofing systems made with SBS tend to be very flexible, have great elongation properties, and are great for accommodating building movement and temperature changes without damaging or cracking. These roofs are usually installed using wet heat welding techniques or cold adhesives.

We then have APP-modified bitumen roofing, with APP standing for atactic polypropylene. This type of roofing membrane tends to be a bit more heat resistant than SBS, and also often a bit more affordable.

This method of bitumen roofing is often applied using a torch-down technique, which means that the membrane is heated up with a torch to create a bond with the surface underneath.

10 Pros of Modified Bitumen Roofing

Modified bitumen roofing has quite a few advantages worth considering, so let’s take a look at them right now.


Modified bitumen roofing is known for being extremely durable, as it is impact-resistant, it can hold up against extreme weather, and it is ideal for high foot traffic.


Another big advantage of modified bitumen roofing is that it can last for a very long time. A good modified bitumen roof can last 20 or even 30 years if it is properly installed and maintained. Of course, the trick here is to properly maintain it.


Another reason modified bitumen is so popular is that it also features excellent waterproofing properties. This is because multiple layers help to prevent moisture from leaking into buildings, as well as prevent other types of water-related issues.

Weather Resistance

Yet another advantage of modified bitumen roofing is that it is very resistant to the weather, particularly snow, rain, wind, and even towards UV rays coming from the sun.


Modified bitumen roofing is also very flexible, which is true for both types. The modifiers added to the asphalt allow for great flexibility, which allows the roof to contract and expand with temperature changes and movement underneath, which helps to reduce the risk of cracking and splitting.


Although installing modified bitumen roofing using a torch-down method can be slightly dangerous, there are different methods that can be used, including self-adhesive, cold-adhesive, torching, and mop-down methods.


One of the best things about modified bitumen roofs is that they generally require minimal maintenance. If regularly inspected and small problems are quickly found, maintenance is generally quite minimal.

Ease of Repair

Yet another big benefit of modified bitumen roofs is that they tend to be quite easy to repair. It’s usually very simple to replace or patch up damaged sections without having to replace the entire roof, therefore also being quite cost-effective in this sense.

Energy Efficiency

What you might also appreciate about modified bitumen roofs is that they are very energy efficient, especially if you purchase one that comes complete with a reflective coating or surface, therefore helping you save energy costs over the long run.

Fire Resistance

Finally, this roofing method is also extremely resistant to fires and combusting, making it very appealing for obvious safety reasons.

7 Cons of Modified Bitumen Roofing

Let’s now take a quick look at the biggest drawbacks of modified bitumen roofing.

Professional Installation

Although modified bitumen roofing is generally not extremely difficult to install, it still requires professional installation.


Although modified bitumen roofing is generally quite durable, one thing that it is not very resilient towards is puncturing.


One of the biggest drawbacks that modified bitumen roofs have, especially as far as residential applications are concerned, is that they just don’t look very nice.

UV Damage

While some modified bitumen roofs are designed to be UV-resistant, those that are not can quickly degrade and crack due to prolonged exposure to the sun.


The cost of installing a modified bitumen roof may be a bit higher than with other roofing systems.


The next drawback of using modified bitumen roofing is that it is not very environmentally friendly, particularly in terms of waste generation.

Installation Odors

If the modified bitumen is being applied using a torch system, the odors emitted can be extremely strong, as well as dangerous.

Should You Use Modified Bitumen Roofing?

If you have a flat roof or low-sloped roof, you need a type of roofing that is fairly easy to install and maintain, doesn’t cost that much, is resistant to foot traffic, and may provide you with great energy savings, then modified bitumen is a fantastic choice to consider.


As you can see, there are both advantages and disadvantages to modified bitumen roofing that you must consider before making any kind of decision here.