Ballasted Roof Systems - Legacy Systems and Why We Rarely Spec Them New

Ballasted roofing was a dominant installation method for single-ply commercial roofs through the 1980s and into the 1990s. The membrane is loose-laid over the insulation and held in place by 1.5-inch river-washed stone at 10 to 12 pounds per square foot - roughly 600 to 720 pounds of stone per roofing square. San Antonio's commercial inventory from that era carries a significant amount of ballasted EPDM and ballasted TPO. The South Side industrial corridor, the older strip centers along Culebra Road and Zarzamora Street, and the Loop 410 commercial ring from the pre-2000 buildout all have buildings running ballasted systems.

Commercial Roofers of San Antonio replaces and maintains existing ballasted systems. We do not, however, routinely specify stone ballast on new commercial construction in San Antonio, and we explain that position directly to building owners who ask about it. The dead-load requirement, the drain accessibility limitations, and the energy code challenges that stone ballast creates in the current construction environment make it the wrong specification for new San Antonio commercial work in almost every case. For the buildings that already have ballasted systems, the question is whether to repair, recover, or replace - and that answer depends on what the moisture survey and deck inspection show.