Rubberized asphalt and flexible PVC don't play well together
Construction is a contact sport so it pays to know the rules when it comes to knowing which materials play well with others.
In the case of materials using rubberized asphalt you should expect staining if you perform a tie-in with a material composed of flexible plasticized polyvinyl chloride (PVC).
That’s because plasticizers in flexible PVC are chemically incompatible with rubberized asphalt. When they come in direct contact with one another, plasticizers dissolve the rubberized asphalt causing it to liquefy. The result is a stained, discolored PVC membrane. (Note: Rubberized asphalt is compatible with rigid PVC, a PVC pipe, for example, and will not be affected when in direct contact with one another.)
Avoiding a damaged PVC membrane when performing a tie in with rubberized asphalt is not rocket science, it’s chemistry. Thankfully, the solution is easy: separate the membranes using a metal or other compatible sealant. That’s it.