Does the thickness of a single-ply membrane matter? Commercial roofing membranes can range from thinner 40-mil, to thicker 90-mil. A common misconception about single-ply membranes is that thicker is always better. While the thickness of a membrane should be considered, it’s not the only factor when it comes to evaluating the quality of the roofing membrane.
Although called “single-ply,” these roofing products are composed of three layers: top and bottom layers of film and a scrim layer that’s sandwiched between during manufacturing. Roof performance is a balance between film formulation, membrane thickness, and reinforcement provided by the scrim. Film formulation determines the flexibility of the membrane and its ability to resist crazing and cracking over time, plus protect against ultraviolet (UV) radiation.
Membrane thickness provides protection from water, snow, and ice elements. To increase overall membrane thickness, some manufacturers add more material to the bottom film layer but little to the exposed layer. However, increasing bottom layer thickness does not necessarily increase membrane performance. The thickness of the film layer above the scrim is far more important.
The scrim is a mesh of small, interlaced threads. Reinforcement provided by the scrim layer provides the membrane’s strength. The scrim protects against natural elements such as wind and hail, and from human activities that can cause punctures and tears. Additionally, reinforcement gives dimensional stability to the membrane and strength against building movement.
Selecting the right membrane thickness for your commercial roof depends on many factors. In some cases, the manufacturer may offer longer warranties on thicker membranes. Thicker may be required under – for example – vegetative or solar roof systems. Do you have a lot of foot traffic on your roof? A thicker membrane may be in order. Thinner membranes that are engineered to high standards should come with a minimum of a 15-year warranty – a typical lifespan for a commercial roof.
Regardless of the “right” membrane thickness for your roofing situation, make sure it’s made with quality and installed by a reputable contractor who is experienced in that type of system.