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Roofing/Is SA method better or APP method for Modified Bitumen


Hi Brad,
I have 3 quotes to redo my flat roof. 2 roofers quoted using
CertainTeed SA 3 layers modified Bitumen and 1 roofer quoted using 3 layers APP modified Bitumen method. Which method; Self Adhering or Torch method in your opinion is a better one for a flat roof.

They are 2 different kinds of roofs. The SA is "Self-Adhering". It's a newer idea. For me it hasn't been time tested yet. The APP is the more common type and is usually installed by torching it down.

Both are really one ply systems. Everything is in one layer. The 3-ply refers to the installation method.
Layer 1 is the base sheet which can be nailed or hot mopped. Nailing it leaves most of the roof loose and therefore is not a good method. But does the roof even need a base sheet? Usually not but if you're installing to bare wood or a bad surface you first use a base sheet. This also applies to the APP rubber.
Layer 2 is the main rubber sheet
Layer 3 is a cap sheet which is like putting 2 roofs on. It is a granule surface maternal but you can do either type of roof with just the granule material or with the smooth finish too.
I like to do my roofs in smooth materials and then aluminum coat the roof afterwards to give it a reflective surface. The white granule material is not as reflective and when done it leaves a lot of black marks that need to be fixed or leave the marks.

Doing the 3ply in either system is really overkill and is usually found in expensive specs for commercial properties. If you're doing a roof on a million dollar office building you take extra precautions that no leaks occur or it could wipe out millions of dollars in computers or tech equipment. The 3 plies is usually not done on a house. Houses usually get the 1 ply roof.



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Brad Zacharia


All aspects of residential Roofing. This includes shingles and flat (low slope) roofs. I have knowledge in the installation as well as the design of roofs from an engineering standpoint.


I have been doing roofing for 40 years. This was my father's business and I took it over in 1980.

I have written responses to artcles that I felt needed a response to and those responses have been published in roofing trade magazines.

BSEE Drexel University

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