Roofing
Part 1: Understanding Single-Ply Roofing Failures Helps Prevent Them
Part 2: Pitch Pockets, Water Vapor can Cause Single-Ply Roof Trouble
Part 3: Improper Use of Adhesives can Lead to Single-Ply Roof Failures
Part 4: Deflection, Crushing of Roof Insulation Can Contribute to Single-Ply Roofing Failures
Improper Use of Adhesives can Lead to Single-Ply Roof Failures
By Amrish K. Patel and Matthew J. Normandeau - February 2012 - Roofing
Improper use of adhesives in roofing systems can result in failures in the membrane or insulation components of the roof assembly. Many factors must be considered when using adhesives in roofing systems.
Two types of adhesives are generally used with single-ply roofing systems: foam adhesives that are spray-applied and liquid adhesives that can be applied by spray, brush or rollers. Foam adhesives are typically used for adhering insulation and cover boards to the structural deck or to themselves, while liquid adhesives are used to adhere the membrane to insulation and cover boards, and even directly to other substrates such as wood, metal and concrete.
There are many causes of adhesive failures and some are more difficult to identify than others. Common causes include improper mixing of adhesives, application when temperatures are below manufacturer recommendations, insufficient or excessive drying time, improper ribbon spacing and width with foam adhesives, and over- or under-application of adhesive. Other issues include improper installation of materials over adhesives, such as not rolling the membrane into the adhesive and not properly "walking in" or pressing insulation and cover boards into the adhesive for even adhesion. One of the most common problems with insulation adhesives is that the boards are not "walked in" long enough, so when the load is removed the board comes unadhered again.
Any one of these installation errors can single-handedly cause adhesive failure in the roofing system. Adhesive manufacturers typically provide thorough installation instructions as well as storage and handling requirements for the adhesives. It is essential that facility managers specify that the instructions and requirements be carefully followed to achieve adequate adhesion. Improper application of adhesives is often not discovered until failure occurs, typically during wind storms which cause the roofing membrane or insulation and cover boards to pull away from the adhesives. While it is possible to achieve successful installations using adhesive systems (as opposed to mechanical fasteners), all parties to the roofing installation must take appropriate care during installation to maximize the quality of the installation and avoid the common problems discussed above.
