“What do you mean my roof is no good? It's a Rubber Roof!”
For building inspectors, it's a question we field far too often. The fact is, in the residential market, so called “rubber roofing” has created more problems than it's solved.
The term “rubber roofing” is typical - and often erroneously - applied to a wide range of contemporary roofing products, ranging from real rubber-like EPDM systems, to more common modified bitumen systems which exhibit few rubber-like properties. These systems, which share the common characteristic of usually being single ply systems, have gained considerable market share in the United States for low sloped or “flat “ roofs. Although these contemporary roofing materials are often touted as better solutions to low sloped roofing, they often fail to meet the homeowner's expectations for performance and reliability. In other words, they leak more often and in less time than people expect.
The problem is typically related to installation defects, and not to the inherent performance characteristics of the material. In most commercial applications, these newer roofing products often do outperform older roofing technologies - but the opposite is true in residential applications.
Prior to the mid 1980s, most low sloped or flat residential roofs were covered with a built-up roof (BUR), system. The conventional BUR system - often called a hot roof, or a tar roof - employs rolls of roofing felt installed in layers, with an intermittent layer of bitumen (asphalt or coal “tar” pitch). In a conventional BUR, there are usually three or four layers or plies of the felt and bitumen combination, giving the system redundant reliability. If the roofing contractor fails to set a field seam perfectly, the redundant nature of a BUR still allows it to perform satisfactorily.
With a rubber or single ply roof (SPR) system, however, there is virtually no acceptable margin of error. If even one field seam is not sealed properly, leaks will result. It has been our inspection experience that for a significant percent of residential roofers, a near-perfect installation is just not a reasonable expectation for the homeowner, Subsequently, we see far more premature failures in residential SPR roofing than we do in older, lower-tech BUR systems.
Nearly every major manufacturer of SPR systems has a training and certification program for selected installers. These same companies will often provide a “system” warranty for their SPR products, when installed by a certified contractor. Unlike a standard materials warranty, the system warranty covers installation-induced defects. The caveat, is that no major manufacturer will provide a system warranty for a residential application. What the industry fears is that the high-quality applications common to commercial installations will not be duplicated in residential applications. When a system fails due to poor installation, the homeowner has no recourse against the manufacturer.
If you simply must have a “rubber roof”, it's essential that the installer be well screened. At a minimum, demand to see proof of the installer's certification by the selected material manufacturer, and select an installer who will provide his own system warranty. Or, even better, bounce back to older and often more reliable BUR systems!