FACTS about Public Roofing Procurement, and Oversight. Copyright 2010 by Robert R. Solomon

Friday, November 18, 2011

"Principle of installing Modified Bitumen Roof Systems"

Sounds pretty easy doesn't it?  Well, today I'd like to introduce a couple of words (and definitions) you often hear from people describing roof systems.

The first word we will focus on is :  "Bitumen"

From Wikipedia:

Asphalt /ˈæsfɔːlt/ ( listen) also known as bitumen is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch. Until the 20th century, the term asphaltum was also used.[1]
The primary use of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.
The terms asphalt and bitumen are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, asphalt (or asphalt cement) is the carefully refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called bitumen. Natural deposits terminology also sometimes uses the word bitumen, such as at the La Brea Tar Pits.
Naturally occurring asphalt is sometimes specified by the term "crude Bitumen"; its viscosity is similar to that of cold molasses.[2][3] whilst the material obtained from the fractional distillation of crude oil (boiling at 525 °C (977 °F)) is sometimes referred to as "refined bitumen".

Refined Asphalt (Bitumen)

Reports indicate that Asphalt production is generally 80% for road building materials, and 20% for roofing materials.  And folks, that's a lot of oil being either laid on the ground, or placed atop your home, or business.

Many people are confused as to "White" modified bitumen roof systems (I will describe the "Modified" portion in a moment).  It has a VERY LOW solar reflectance, and can reach temperatures of 200 degrees F., adding to energy demands.

Here is a crew installing "Modified Bitumen"

Okay, someone is on the ground feeding 100 lb. cartons of asphalt into a kettle, typically heated with propane burners to a temperature of around 425 degrees F.  I've personally "fired" one of these monstrosities, and would not wish it on my worse enemy.  This job is typically referred to either the "kettle man", or the "fireman".

Wouldn't you like to spend around 10 hours a day in the hot sun wearing full coverage clothing, and a face mask?  The pieces can easily "splash" the molten asphalt onto the workman, and you will keep in mind he is chopping 100 lb. cartons of this all day.  It is much easier in the morning when the asphalt is cool, and when you strike it with an axe, is almost "glasslike" and splits fairly easy.  Onced  it warms up, the asphalt becomes "gooey", and the axe simply sticks.

The hot asphalt is pumped to the roof, and collected into "hot luggers"

Okay, we've heated up the asphalt, pumped it to the roof through a steel pipe, loaded it into our "hot lugger", rolled it across the roof, and emptied it into the "Mop Cart".  You can see the guy using a roofing mop, the other guy is the "setter", and the other is casting ceramic granules into the asphalt "bleed out".  Sometimes referred to as "Feeding the chickens".

Here is a finished Modified Bitumen roof:

You will note the letters "SBS", and "APP".  They stand for:

"Styrene Butyl Styrene" : (Thank you to Johns Manville)
"SBS is a rubberized modifier that increases the overall performance of the sheet by providing excellent elongation and recovery characteristics. SBS modifiers extend the service range of the product, so that it can be handled in cooler temperatures without cracking or shattering, and in warmer temperatures without softening to the point where it begins to flow".

This material is applied with the "hot mop" method as illustrated above.

APP: Atactic Polypropylene

"Johns Manville has developed formulations that enhance the asphalt's overall weatherability by modifying premium-grade asphalts. By combining these modified asphalts with non-woven polyester or glass fiber reinforcements, JM produces waterproofing systems that exhibit tremendous strength, elasticity and weatherability.

APP membranes provide superior tensile strength while maintaining critical flexibility — even in the coldest environments. Additionally, with APP roofing membranes (coated with a proprietary blend of asphalt and atactic polypropylene), contractors now have an efficient mode of application by heat welding, making hot mopping unnecessary".

This is what "Torching" looks like:

MANY people hear the term "Rubberized Asphalt", and think they are geting a "Rubber" roof.  This is obviously not the case.  The "Rubber" is a "Modified Polymer".

The roof repels water, but given what we know is a very archaic, and dangerous method.  Also consumes huge quantities of materials that will never break down in landfills, and contaminates water supplies through leaching of nitrogen and phosphorous.

This is obviously not my choice of roofing methods, but it does in fact "keep water out".  It CREATES great demand  in HVAC cooling (approximately 20%).  So if you live in a warmer climate (most people do), this would not be your best option.  Modified Bitumen roof systems typically have a Solar Reflectance Index of .25 (similar to asphalt shingles.  For the record, (according to LEED V2.2, Page 95), the minimum Solar Reflectance Index for a cool roof to mitigate "Heat Island Effect" is .78.  So you can see this is clearly anything but a "Cool Roof".

Today is a very good day, I am happy you are sharing it with me, and always remember to keep looking "UP".


Robert R. "Ron" Solomon
Manager, Roof consultant's Alliance


  1. For the future you may want to quote LEED correctly, since you're an expert and all. LEED v2.2 has been replaced now for 3 years and LEED 2009 is about to be replaced in 2012. And it's Solar Reflective Index not Reflectance. Also, SRI is a whole number not a decimal. You're confusing SRI with reflectivity. Reflectivity is a percentage of UV rays reflected, SRI is a formula that takes reflectivity and emissivity into consideration.

    I've been working with mod bit, single plys, and coatings for 5 years, primarily for LEED projects. To group all mod bits in the category you described above is irresponsible. Yes, some mod bits are torched down still but most use cold applied adhesives now. Almost all modifieds out there have a high reflective option which you can see if you search on the CRRC's website. In fact there are 33 different sheets out there that meet LEED's SRI standard of 78.

    I don't know if you've been out of the game for too long and aren't doing your due diligence to keep up with the times or you have some kind of personal vendetta against someone. In any case most of this "article" is just false by today’s standards.

    “The trouble with internet articles is that you never know if they are true” – Abraham Lincoln

  2. Cool Earth founder Brian Yauger has installed roofing for just about every climate variance across the USA.Cool roofing is the fastest growing sector of the building industry, as building owners and facility managers realize the immediate and long-term benefits of roofs that stay cool in the sun. This site offers Epoxy Floor Austin, Cool roofs, Commercial roof, Epoxy coating, Foil radiant barrier, Reflective roof . They have 10-years of Roofing and General Contracting experience, You will be glad you decided to work with them.

  3. Someone tell the guy rolling out the cap sheet to get off of it! Roofing 101- stay off the rolls while applying!
    In the finished mod bit photo there are 2 seams lined up in the area of the 2 vent and soil stack penetrations. Min off set of seams is required . There are residential type pipe boots and vents used in a low slope application...
    So far we have improper application methods, improper seaming, improper flashing.... Nice job!

  4. Reject negativity in all forms? Who are you trying to kid, besides yourself? Stunningly bad article on the basics of roofing.

  5. This comment has been removed by the author.

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