Commercial roofing (i.e. low-slope) jobs come with a lot of variables. Many projects are large in scope, utilize any variety of bituminous application methods, and require tools ranging from kettles of hot asphalt to blow torches. A lot can happen in terms of efficiency and safety that either moves projects along or delays them for weeks at time. Commercial projects also often come with built-in penalties for construction delays that impact a business' revenue.

For all the reasons above, commercial contractors are always looking for ways to speed projects along without sacrificing safety or quality. While single-ply roof coverings like TPO (thermoplastic polyolefin) have become a common standard for low-slope applications, newer, self-adhered solutions have emerged as an alternative to roof coverings that require torch-applied or hot-mopped asphalt. these self-adhered base and cap sheet products can be rolled out and applied like a powerful sticker to most roof surfaces, but when time is money, do self-adhered products really save the contractor time?

Weighing the Pros and Cons of Self-Adhered and TPO Roofing

TPO single-ply roofing systems have been on the market for more than half a century, so most commercial roofers are familiar with how TPO installs and performs. TPO systems are typically durable; effective in resisting bacteria, debris, algae, as well as ultraviolet (UV) exposure; and relatively low in cost.

Self-adhered modified bitumen roof systems come with many of the same qualities, however, with several advantages. Self-adhered roof systems are installed in two or three layers, reducing the risk of leaks compared to a single-layer installation. Manufacturers have yet to resolve cracking, erosion, and other performance issues that can occur in TPO single-ply roofing membranes after installation.

TPO single-ply roof systems range between 1 and 2 mm (40 and 80 mils) in thickness, while most self-adhered roof systems range from 5 to 10 mm (180 to 380 mils), making self-adhered systems less susceptible to puncture from foot traffic, dropped tools and minor installer errors.

Judging Speed

To answer this question of speed definitively, Certainteed commissioned a labor study to help commercial roofing contractors improve labor efficiencies and determine which low slope roofing methods were the fastest. To do this, a third-party consulting firm observed the installation of 45 different low-slope roofs with six different roof covers in 18 different configurations across various regions of the U.S. over a five-year span.

Like commercial roofing itself, the study took into account many variables, including project size, climate, installation methods, flashing details and installer errors. While there are no "one-size-fits-all" solutions in the commercial roofing market, third-party data concludes several important details about the speed of self-adhered and TPO applications:

• In a controlled setting, data shows the fastest installed roof covering is a two-ply bituminous system with a mechanically-attached base sheet and a self-adhered cap sheet; the slowest installed system is a bituminous system with both the base sheet and cap sheet installed with hot asphalt.
• On average, a self-adhered roof cover requires 54.2 labor minutes per square while a mopped cover requires 156.5 labor minutes per square - a difference of 102.4 labor minutes per square (2.89 times) or $38,390.63 in estimated project labor costs.
• A bituminous roof cover consisting of a mechanically attached base and a self-adhered cap has a faster installation time than the same base sheet covered with either a torch-applied or hot-mopped cap sheet or a single layer of TPO.
• Flashing details (particularly base flashings and curbs) account for a larger percentage of labor on a single-ply projects in comparison to multi-layer bituminous projects.