The KEE to PVC – Membrane Roofing

Published by Don Hester on October 22, 2020October 22, 2020

Membrane roofing, specifically single ply membrane roofing can be a great choice on flat roofs. There are several materials that can be used. Many of the newer roofs are using plastic (Thermoplastic) types of membranes. Most have heard of PVC, EPDM, TPO but let’s add one more to the list KEE. Often field identifications can be tough on some of these membranes. I typically will look at the penetrations and boots and look for a stamp on them.
 
                                                                                                                                                     

PVC is polyvinyl chloride, TPO is Thermoplastic polyolefin, EPDM is Ethylene Propylene Diene Terpolymer, and KEE is Ketone Ethylene Ester. Like everything there are pros and cons to each material. 

The big issue with PVC is that it was more rigid and they added plasticizers (softeners), typically liquid, to make the PVC more flexible. The issue with these liquid plasticizers is that UV will cause the plasticizers to leak out over time causing the membrane to dry out and become more prone to cracking. The positive of PVC is that in some condition this type of membrane will be more resistant to some chemicals and oils.

TPO came in to help address some of the shortcomings of the PVC but is less flexible and may be more prone issues from chemicals and oils. So in some application it may not be the best choice. EPDM is a synthetic rubber and is naturally a black membrane but may have a white laminated top. EPDM generally they are more expensive but can be a good material.

General life spans of the different Membranes is TPO- 15-20 years, PVC – 20+ years, EPDM – 20-30+ years.

– Study on lifespans –

Now with many of these membrane they are working on different formulations to address some of their inherit weaknesses. 

So now let’s look at KEE, now to till recently I really did not know much about this specific membrane. The estimated lifespan is 30+ years. Turns out this type of membrane has been around for a while, 40+ years but I never have come across them  that I knew of till recently. 

To be called a KEE membrane it has to be have 50%+ or more of KEE (KEE – ASTM D6754). To be called a PVC it has to have 50%+ PVC (PVC – ASTM D4434), semantic, semantics, semantics. They mix KEE to the PVC to maintain flexibility over time because KEE is a soft and flexible polymer that is not liquid making it more resistant to UV evaporation which will cause PVC to dry out. They still will have PVC in the KEE membrane for welding purposes.

There are several KEE membrane manufactures such as Fibertite, Duro-last, TremPly

Fibertite
Durolast

TremPly

There are also some PVC listed materials that will have higher levels of KEE such as John Manville’s JM PVC with DuPont Elvaloy KEE Polymer . 

So when looking at these membranes know that these various types will have different lifespans and disabilities. When looking at them try to look at the penetrations for identification. Another item is there are some boots that can be used on various membrane types so it may not be conclusive.

If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.

NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…  

Your Wenatchee and Chelan Professional Real Estate, Home and Structural Pest Inspection Service

Coordinator & Instructor- Fundamentals of Home Inspection-  Bellingham Technical College

Former WA Home Inspector Advisory Licensing Board

www.ncwhomeinspections.com                                                   509-670-9572

 You can follow me on Facebook, Twitter, Google+ and on my website Blog.

If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.

NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…  

Your Wenatchee and Chelan Professional Real Estate, Home and Structural Pest Inspection Service

Coordinator & Instructor- Fundamentals of Home Inspection-  Bellingham Technical College

Former WA Home Inspector Advisory Licensing Board

www.ncwhomeinspections.com                                                   509-670-9572

 You can follow me on Facebook, Twitter, Google+ and on my website Blog.

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