Modified Bitumen Roofing Option

As contrasted to BURs, which rely on field application of bitumen to make them water resistant, polymer-modified bituminous sheets (MB) take advantage of strengthening sheets that have actually been factory covered with rubberized bitumen. The usage of polymers blended with the covering bitumen enhances versatility, strength, and low-temperature level buildings.

Classifications of MB systems consist of:

– Liquid solvent-based adhesives.

– Heat-fused, where a gas torch or hot-air welder is utilized to re-melt the factory-applied bitumen to act as an adhesive.

– Mopped-in-place, utilizing traditional hot BUR strategies.

– Self-adhesive (peel and stick).

Two plies of enhancing sheets are utilized to build the membrane. The base layer might be a customized sheet, a traditional asphaltic base sheet, or numerous layers of BUR ply sheets laid in hot asphalt. (The latter system is often described as a “hybrid system.”).

Polymer Modifiers

Both elastomeric products and thermoplastic modifiers are utilized. Thermoplastics consist of atactic polypropylene (APP), alpha-polyolefins (APO), isotactic polypropylene (IPP), and ethylene-vinyl acetate (EVA). Elastomerics consist of styrene-butadiene-styrene (SBS), and styrene-butadiene rubber (SBR).

In basic, the thermoplastic sheets (APP types) are heat-fused to the substrate, as the melting point of these sheets is too high to be dependable adhered with hot asphalt. The greater softening point of APP sheets in some cases makes them preferred in sweltering environments while the much better low-temperature versatility of SBS sheets is liked in cold environments.


Glass fiber, polyester, and mixes are frequently utilized, although plastic core products have been utilized in some waterproofing and shingle underlayment applications. The supports bring the sheet throughout manufacture and supply tensile stamina and stability to the completed membrane.


Covered modified bitumen sheets are stiff in winter, and rolls ought to be stored at temperature levels above freezing for 24 hours before unrolling. In some solvent-adhesive systems, the body of the sheet is embedded in the adhesive. However, the side and end laps might be torched to obtain a trustworthy and fast seal. Self-adhering sheets usually need temperature levels above 50-degrees F. to accomplish adhesion, and numerous systems supplement the self-adhesion at T-joints using mastic adhesive.

Usage of Propane Torches

Torch application is appealing because the heat of the torch makes the MB sheets more conformable. Fire districts might need day-to-day reporting when gas is being used, and might restrict the usage of torches entirely in occupied structures. The Certified Torch Applicator (CERTA) program is provided by both the National Roofing Contractors Association (NRCA) and the Midwest Roofing Contractors Association (MRCA).

Cold Adhesives

Both unmodified and polymer-modified bituminous adhesives have been utilized. Water-based adhesives can not be made use of since the MB sheets are impenetrable, and the water can not get away. Some systems torch or heat-seal the side and end laps to fix the curling issue.


Vertical flashings for many MB systems need can’t strips to minimize the angle at the base of the wall or curb. (Fire-retarded pants are required for torch systems.) MB flashing products have been so thorough that it is appealing to get rid of the requirement for a backer sheet; nevertheless, for optimal waterproofing and sturdiness, a backer sheet is still suggested.

 We, at Reilly Roofing & Gutters, want to make sure that from the initial introduction to the end of your project is second to none. 

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