The case for metal-over-metal retrofits

By The Coffee Shops®. 

Roof Hugger experts explain how structural attachment, drainage, longevity and future rooftop needs can shape retrofit decisions. 

When recovering an existing metal building roof, contractors and building owners must consider more than the initial installation price. In one episode of MetalCast™, Heidi J. Ellsworth spoke with DJ Highnote and Dale Nelson, vice president and president of Roof Hugger respectively, about how metal-over-metal retrofit systems can address structural performance, water movement and long-term building needs. 

One of the primary distinctions discussed was how the new system attaches to the building. DJ explained that a metal-over-metal retrofit can actually strengthen the roof system because of how it is installed. “When you're doing a metal over metal retrofit, you're getting an actual structural attachment to the structure underneath the panels,” he said. This approach can also be engineered to address wind uplift, snow loads and the condition of the building’s purlins. 

Water management is another important consideration. Dale explained that metal buildings are designed to channel water along the roof panel ribs and move it quickly toward the gutter or eave. A flat recovery surface can change that drainage pattern, potentially directing water toward areas where the framing deflects. “Sheet flow is never how metal buildings are designed,” Dale said. “They’re designed for channeled flow.” 

Dale and DJ also encouraged contractors to evaluate expected service life and future use of the roof. While other options like thermoplastic polyolefin (TPO) as potentially less expensive initially, they said metal can provide a longer service life. That difference becomes especially relevant when building owners plan to add photovoltaic panels, which can be mounted externally on a metal roof without penetrating the roof panel. Energy performance can be incorporated into the retrofit design as well. Depending on the building and its location, the cavity between the existing and new roofs may be insulated, ventilated or designed with both strategies.  

Together, these considerations give contractors an opportunity to discuss retrofit value in terms of structural attachment, drainage, safety, energy performance and future rooftop investments. 

Listen to the podcast or Watch the recording to learn more about metal-over-metal retrofits.