SpecTopics: PVC Roofing Membrane and Rubberized Asphalt

Determining the compatibility of the materials used for each subsystem of the building envelope can be a difficult task. Many manufacturers do not have testing that confirms the long-term compatibility of their materials with materials by others. However, one well-known compatibility issue is between PVC and rubberized asphalt. You will experience compatibility issues when tying an air or vapor barrier which uses rubberized asphalt adhesive on an exterior wall to a PVC roofing membrane on the roof deck or parapet wall.

Flexible PVC roof membrane is known to not “play nice” with the rubberized asphalts that are typically used as the adhesive on peel-and-stick air barrier products. The rubberized asphalt can pull the plasticizers out of flexible PVC membrane, causing brittleness or cracking. The plasticizers can also cause the rubberized asphalt to turn to a liquid and run down the PVC membrane.

Always be mindful of the sequencing when tying PVC to peel-and-stick membranes to avoid unwanted contact. The solution is to separate the membranes using metal or compatible sealant.

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To learn more about roof-to-wall tie-ins, check out the NVELOP details on Carlisle’s NEVELOP website or click here and look for the complete detail packet. 

If you have any questions regarding PVC roofing membrane, please contact Dan Allen at [email protected]. If you have any questions regarding NVELOP, please contact Chris Kann at [email protected].