SBS Modified Bitumen Products for a Leak-free Roof

cold applied sbs modified bitumen

Photo: GAF Applied SBS brochure

SBS (styrene-butadiene-styrene) modified bitumen cap sheets have been around for decades. First developed in Europe in the 1960s, it was designed to incorporate the benefits of the proven built-up roof system with the revolutionary polymer chemistry. The result was a premium roof system that out-performs all other conventional low slope roof systems.

Some of the benefits of SBS modified bitumen products are that they can be installed in a variety of ways. The type of facility, location, access, deck and insulation type, climate and customer requirements are few of the reasons of the various application methods.

Modified Bitumens can be:
Hot Applied
Cold Applied
Torch Applied and

There are 4 Key Components to Any Successful Roof System:

• Specific Specifications and Details Tailored for the Particular Project.
• Skilled Workmanship
• Quality Products
• Regular Inspection During and After Installation

Prior to the installation of the Hot Applied Modified Bitumen Roof Systems, there are several items that must be reviewed. Ridge Top Exteriors of St. Louis takes responsibility that all safety precautions are in place. Materials will be stored properly and protected from the weather with a breathable waterproof covering. Wet materials will be removed from the job site and replaced with dry materials. All raw materials will be stored in such a way to prevent them from becoming deformed or damaged.

Cool temperature and precipitation will affect the application of the Hot Applied Modified Bitumen Roof System. Ridge Top Exteriors doesn’t install SBS modified bitumen cap sheets during precipitation because the chances of blisters are greatly increased. SBS modified bitumen rolls, base sheets and asphalts become less flexible at low temperatures. As temperatures begin to drop, the chances increase that modified bitumen sheets will be required to be rolled-out and allowed to relax. Thicker, more robust modified sheets and sheets with a hefty amount of fiberglass or those with extremely high tensile strength will be more likely to require relaxing prior to installation.
sbs modified bitumen commercial roof

Photo: GAF Applied SBS brochure

The amount of time required for relaxing the sheets is based on several factors including the nighttime low temperature, amount of sunlight and membrane thickness. In some cases, it will be necessary to unroll and cut the raw materials to a maximum of 18-foot lengths to allow for its relaxation before and after application. These application procedures will minimize occurrence of wrinkles and buckles.

Insulation must be secured properly to the structural roof deck. To ensure that specified fastening patterns are followed with particular attention to corners and perimeters.

The most critical part of a Hot Applied Modified Bitumen Roof Systems is the asphalt temperature. At the point of application of the modified bitumen, the mopping asphalt should be applied to its Equiviscous Temperature or EVT. Adequate asphalt temperatures are essential for adequate adhesion of SBS modified membranes. Asphalt is typically installed at a rate of 25 pounds per layer of roofing material. Layers of very hot asphalt are designed to melt the back of the bitumen cap sheet to create a bond between all plies of the roof.

Ridge Top Exteriors located in Florissant, MO will educate the building owner before the installation of SBS modified bitumen products so they are familiar with the safety precautions that will be performed to achieve quality and leak-free roofing.