Modified Bitumen Roofing

 In Blog

A Membrane Roofing is a kind of roofing system for buildings, tanks, residential applications and other commercial applications where it is commonly used to move the water off of the roof. It is usually made from synthetic rubber, modified bitumen, or thermoplastics such as PVC or other materials similar to it.

A Synthetic Rubber or also known as Thermoset is a type of membrane roofing that is made of materials that chemically crosslink. These large, flat pieces of synthetic rubber are bonded together at the seams to form one continuous membrane. These types of membranes are commonly thick where it is usually has a thickness of 30 and 60 mils.

The most commonly used Synthetic Rubber membrane is EDPM. Another type of membrane roofing is the Thermoplastic Membrane. The thermoplastic membrane is similar to a thermoset membrane but its seams are naturally heat fused or welded and there is no chemical cross-linking to form a continuous membrane. The lap seams of the thermoplastic membrane can also be fused with a solvent instead of heat and can still be as strong as the rest of the membrane. Modified Bitumen membrane is a type of membrane that conglomerates asphalt with modifiers and reinforcement materials. There are a lot of ways to connect the pieces of this material. It can be in a heat application process where the seams are heated to melt the asphalt together and create a seal on it. It can also be via hot-mopped application where the installation is just alike with how conventional built-up roofs are setup.

SBS or APP membrane type

There are more other ways in connecting the pieces of these materials like cold-applied adhesives and self-adhesive membranes. The common types of these membranes are SBS or Styrene Butadiene Styrene and APP or Attactic Polypropolene.

An SBS modified bitumen membrane is an elastic asphalt or a synthetic rubber. It has a low-temperature flexibility of -22 degrees Fahrenheit to -5 degrees Fahrenheit. Its softening point is at 230 degrees Fahrenheit to 270 degrees Fahrenheit.  An SBS also has an elongation with a full recovery rate of greater than 1000% with a serviceability range of -20 degrees Fahrenheit to 270 degrees Fahrenheit. When using the SBS, it increases the flexibility of the membrane and let it have a sturdier expansion and contraction capabilities.

On the other hand, an APP modified bitumen membrane is a plastic asphalt. It has a low-temperature flexibility of 14 degrees Fahrenheit to 32 degrees Fahrenheit. Its softening point is at 245 degrees Fahrenheit to 300 degrees Fahrenheit.  An SBS also has an elongation with a full recovery rate of 5 – 10% with a serviceability range of 15 degrees Fahrenheit to 300 degrees Fahrenheit. When using the APP, it increases the aging ability of the roof system. The Modified Bitumen also do come with disadvantages; since it has a black color, it absorbs heat than reflect it, if it is not properly installed the building below can superheat. In contrast, having bitumen roofing with a 2 or 3-ply material and is coated against a UV exposure with proper bitumen roof job, Modified Bitumen is the best roof you will ever have.

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