Its good practice to create a sill pan flashing prior to installation of a window?
After contacting most all major peal stick membrane suppliers I find none of their products are to be used with “standing water” or are warrantied at all with this application! They tell me water must shed. Its difficult to impossible to shed water off a flat sill surface.
Shimming the sill to slope places the window out of plumb and jeopardizes the warranty.
Am I looking to use sheet metal of some kind or?
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