This is what happens when roof coating or any other elastomeric products are applied to parapet walls. I know, It sounds like a great idea and many contractors still try to sell this as an add-on.

Here’s the process… As the elastomeric products shift and eventually crack, they allow moisture to seep in and get trapped. The moisture in effect rots the stucco and rusts the metal lath. When the sun heats-up these areas it causes steam and pressure under the surface and buckles the stucco. It’s a costly repair-