Tapered rigid insulation, also known as polyisocyanurate insulation, it is manufactured to provide a slope in flat roof applications. The first piece may go from 0.5” high to 1” high , then the next piece will go from 1” high to 1.5” high. These pieces of insulation are generally 4X4 feet in size, some local Toronto roofing suppliers have standard pieces available for purchase at all times. Standard stock pieces are the best option if you are looking for a budget tapered solution, keep in mind you need to plan the project prior so you know exactly what pieces you require. Over the course of the roof system, the tapered insulation will create a slope toward the drain, scupper or gutter. A tapered roof system is completely customized for every single roof by a roofing consultant or a dedicated division within most commercial product suppliers. I have worked on many projects where I was able to provide a good tapered system using standard stock pieces and therefore providing great value to my client. In most commercial flat roof applications the engineer or consulting firm overseeing the project will specify whether a tapered insulation system is required. In all cases tapered insulation adds to the cost of the project because of material and the additional labour costs required to lay out the pattern of pieces.
Generally tapered rigid insulation is useful on roofs that have excessive water ponding issues. The cause of most ponding is related to the contours of the existing structural deck. It is understood by industry professionals that tapered insulation aims to reduce or eliminate the problem by creating a slope toward the drains, which water will follow. While tapered insulation may not stop all ponding, it helps significantly reduce it. I can’t stress the last point enough.