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Roofing/SBS Modified Bitumen vs APP modified Bitumen

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Question
Hi Bruce,

I have 3 roofers came to give estimate on my flat roof. I live
in San Francisco, Ca. 2 roofer quoted using CertainTeed Self Adhering Modified Bitumen (base, ply,cap). One roofer quoted using APP CertainTeed Modified Bitumen(base, ply, cap). The ones
using self-adhering modified bitumen method is more expensive.
Which method is better and last longer? Please help. Is CertainTeed a good brand?

Thanks,
Nelly

Answer
Nelly,

CertainTeed is a fine manufacturer and either product is comparable to the other.  The Modified bitumen has rubber based additives blended into the asphalt base to make it more resilient at low temperatures.  The APP is modified with plasticizers which do the same thing.  The APP has certainly been around much longer than the self adhering style of modified but the down side is that the APP is typically installed with a torch or heat welder so there is additional risk of fire.  The APP can be installed with adhesive, but better to go with the Modified if you are not OK with the torch applied method.

With either option please make sure you observe the installation at some point before it is complete to be sure you receive a base sheet (which is typically nailed to the wood deck - or through the previous roofing layer) followed by a ply sheet which should be much heavier and smooth and black on both sides, followed by a top ply sheet which will typically have a surface of mineral granules for a Class A fire rating.  Sometimes the intermediate ply sheet gets left out for various reasons.

Regards,

Bruce Ryan II, RRO
Professional Roof Consultants, Inc.

Roofing

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Bruce A. Ryan II, RRO

Expertise

I offer solid knowlege of all types of Commercial and Residential Roofing, Waterproofing, and, Building Envelope systems. Experience ranges across low slope and steep slope roof systems. I am also well versed in matters regarding condensation and ventilation. I enjoy donating some of my time and knowledge to the betterment of others.

Experience

Bruce Ryan has 20 years of roofing, waterproofing, and building envelope consulting experience with PRC, with 5 years of commercial roofing experience prior to joining the firm. He became Vice President of the company in 1998. Bruce Ryan plays a key role in the development of practical, long-term roofing and waterproofing solutions, along with implementation of on-site forensic studies. Bruce also has a high level of experience with regard to the impacts of roofing materials and construction for demanding clients with heavily occupied structures.

Organizations
Oregon Construction Contractors Board Construction Specifiers Institute National Roofing Contractors Association The Institute of Roofing, Waterproofing, & Building Envelope Professionals Oregon Board of Investigators Installation Masters

Education/Credentials
University of Maryland BS Business & Administration Registered Roof Observer - RCI Private Investigator Certified EIFS inspector - Northwest Wall and Ceiling Bureau Certified InstallationMaster™ - The Installation Masters™ Training and Certification Program (developed by American Architectural Manufacturers Association)

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