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What is a modified bitumen roof?

Modified bitumen, also known as Mod Bit, is more common on residential roofs but is also used on commercial roofs. Although it has a lot of advantages, it isn't for everyone. Continue reading to learn what a modified bitumen roof is, how long it lasts, how much it costs, the benefits of a modified bitumen roof and more.

Before we talk about modified bitumen, what is bitumen? (pronounced 'bit-oo-men') Also known as asphalt, in layman terms, bitumen is a thick, sticky, black liquid.

What is modified bitumen?

Modified bitumen is bitumen that has rubbers or plastics added to it then adhered to fiberglass or polyester fabrics. It was developed in Europe in the mid-1960s and has been used as a flat roof option since 1975. Modified bitumen comes in two types: SBS (Styrene Butadiene Styrene. Most common.) and APP (Atactic Polypropylene). We only offer SBS modified bitumen.

Who uses a modified bitumen roof?

Modified bitumen is used on low slope or flat roofs, either commercial or residential, but more often on residential buildings such as homes, apartments, etc.

How long does a modified bitumen roof last?

10-15 years, on average, depending upon all sorts of factors, such as if it was professionally installed.

How much does a modified bitumen roof cost?

On average, around $4.25/sf. total, for materials and installation. This is just an average. Please contact us for a free estimate for your particular commercial roof.

Advantages and Disadvantages of a Modified Bitumen Roof



Modified bitumen expands and contracts with the changing temperature, so it's tear and crack resistant. It performs extremely well in areas where the temperature fluctuates greatly.

Competitive cost

Costs just a little bit more than asphalt shingles.


Because of the added fiberglass or polyester, modified bitumen has a high tensile strength, which makes it resistant to tears and hail. It also holds-up extremely well in areas with high foot traffic.

Easy to repair

In the rare case modified bitumen does tear, it is quickly and easily patched with bitumen patches.

Easy to install

SBS modified bitumen comes in rolls, which makes it very easy to install.

Water resistant

Oil and water don't mix. Therefore, modified bitumen is extremely water resistant.

Wind resistant

Modified bitumen is a flat membrane that is mechanically attached to the roof deck. Therefore, it is extremely resistant to high winds.

Energy efficient

Although modified bitumen naturally comes as black, a top reflective layer can be added to reflect sunlight, therefore, reducing your energy bill.

Low maintenance

Because modified bitumen is strong and weather resistant, it is naturally low maintenance. That said, it is a good idea to have your modified bitumen roof inspected regularly.

Multiple colors

Modified bitumen comes in many different colors that can closely match shingles. For example, white, black, slate, tan, shake, green, etc.



The only disadvantage of modified bitumen, is its lifespan. At only lasting around 10 to 15 years, it doesn't last as long as other commercial roofing, or residential roofing systems.

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