Walk any Park Ridge alley and you'll see them: low-slope additions added behind steeper main pitches over the last 60 years. Sunrooms, kitchen bump-outs, enclosed porches. They're a defining feature of how Park Ridge homes grew over time — and they're where most of the leaks we see actually originate.
The issue is almost never the flat membrane itself. It's the transition where the steep main roof meets the low-slope addition. Water from the entire upper roof concentrates at that wall — and the flashing has to handle that volume while also accommodating different roof materials and the often-complex geometry of the attachment.
Done right, a low-slope addition roof in Park Ridge typically uses EPDM rubber or modified bitumen on the flat section, with a properly counter-flashed apron at the steep transition, a base flashing that extends up the wall under the steep-roof underlayment, and step flashing where the addition meets a brick wall.
We strongly prefer fully adhered EPDM on smaller residential flat roofs — the seam reliability is excellent and the freeze-thaw tolerance suits Park Ridge winters. Modified bitumen has its place on certain decks, particularly where puncture risk is high.
If you're seeing recurring leaks at an addition transition, it's almost always solvable. Often we don't need to replace the full flat roof — just rebuild the transition flashing correctly.