Could My Parapet Wall Be the Reason My Flat Roof Is Leaking?

Your flat roof may look simple, but the parapet wall has a lot going on behind the scenes. Imagine of it as the roof's security system. If the details aren't installed properly, water can find its way in—and water is an expert at finding trouble.

A proper flat roof parapet wall detail uses several layers working together. First comes Poly ISO insulation (Roof Deck Insulation), which helps provide insulation and a solid base for the roofing system. Then comes the bitumen base sheet, followed by the modified bitumen cap sheet (Waterproof Roof Cover) that helps protect the roof from the elements.

There's also a small but important piece called a cant strip (Triangular Edge Block). Don't let the fancy name scare you—it basically helps turn a harsh 90-degree corner into a smoother transition. Why? Because roofing membranes don't enjoy being forced into sharp corners any more than we enjoy stepping on a Lego.

The wall flashing then extends up the parapet wall, helping keep rain and Chicago snow from sneaking behind the roofing membrane. A counter-flashing is added to help secure everything in place and seal the wall detail.
Finally, the metal coping is angled slightly inward so rainwater flows back toward the roof's drainage system instead of running down the outside wall and creating another problem.

At Anchor Point Roofing, the top-rated roofing company and your go-to roofing company in Chicago, these small details matter. Because when it comes to a flat roof, "close enough" is not a roofing strategy.
A properly installed parapet wall detail keeps water where it belongs—outside your building, not inside your ceiling.

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