Installation Details · FAQ

Which flashing details matter most on an Illinois roof?

Three locations cause 80% of the leak claims Trill responds to: chimney flashing, valley flashing, and skylight flashing. All three sit at intersections where two different planes meet, creating a water channel that wants to find a path inward.

Trill installs step flashing (not continuous flashing) on chimneys and walls, which means a separate piece for each shingle course. On valleys we install a 36-inch wide ice and water membrane below the valley flashing metal. On skylights we use the manufacturer’s matching flashing kit, not site-fabricated alternatives. The cost premium for proper flashing on a typical install is $200 to $400 across all three locations. That’s the cheapest leak insurance you’ll ever buy.