In this episode of Building with Metal, McElroy Metal’s Charlie Smith shares practical insights on how to safely increase the load capacity of existing buildings. From engineering considerations and framing techniques to panel selection and recover strategies, Charlie explains how to balance performance, safety, and cost when modifying existing structures.
Charlie Smith: "US Steel is telling you that they're expecting sixty, seventy years of life expectancy out of the roof system. It would be nice if you could make a simple repair to it, and that's what the symmetrical panels do."
Charlie Smith: "You can't just remove an exposed fastener roof and put a free-floating standing seam on there. I mean, you're liable to have a huge problem... You're always better off, in my opinion, if the existing roof is an existing screw-down panel that's an integral part of the structure, just to leave that in place and then retrofit."
Charlie Smith: "You gotta have a great system, you gotta have a great design, and you gotta have a great contractor. If you're a long-term owner, then a metal roof is probably gonna be the best way for you."
0:00 – Introduction to Charlie Smith and his background in metal roofing, including twenty-three years owning a regional manufacturer before joining McElroy Metal thirteen years ago.
2:30 – Explanation of symmetrical standing seam panels versus traditional double-lock systems, including the fifty-year Galvalume warranty and repairability advantages.
6:00 – Discussion of why buildings need additional load capacity, covering the two main building types: traditional steel deck construction and metal buildings with open purlins.
10:00 – Overview of approaches to increase structural strength, including adding purlins from inside, retrofit systems on top of existing roofs, and grid systems for wind loading.
15:00 – Benefits of recover versus tear-off: avoiding operational disruption, bypassing energy code requirements for R30 insulation, and maintaining structural integrity.
20:00 – Introduction to the Roof Hugger system and its extensive base testing program that quantified structural enhancement capabilities.
26:00 – Explanation of high-floating versus low-floating standing seam identification methods, including interior inspection and drill testing techniques.
32:00 – Case study of a Pennsylvania military armament facility where Roof Hugger solved an eight-pound-per-square-foot capacity deficiency without operational shutdown.
38:00 – Comparison of tall clip recover systems versus EPDM membrane alternatives, including discussion of water channelization requirements for metal buildings.
43:00 – Final advice for building owners considering recover projects and contact information for Charlie Smith.
When a metal building needs a new roof, building owners face a critical decision that extends far beyond selecting materials. Charlie Smith, who spent twenty-three years operating a regional metal roofing company before joining McElroy Metal thirteen years ago, has made a career of solving the complex challenges that arise when recovering existing structures. His expertise centers on a fundamental question: how do you add a new roof to a building that may not have been designed to carry additional weight?
The answer begins with understanding what the building code allows. The International Existing Building Code permits adding up to three pounds per square foot to an existing structure, which sounds generous considering that a typical metal roof recover weighs between one and a half to two pounds per square foot. However, Smith has found that many buildings, particularly metal buildings with open purlins, lack even this modest capacity cushion. "I'd say at least fifty percent of the time, there's not three pounds there," he notes. "They don't even have the capacity."
This reality makes the choice between a recover and a tear-off more consequential than many owners realize. The advantages of recovering an existing roof extend well beyond the obvious benefit of keeping operations running. When you remove an existing roof, you trigger energy code requirements that typically mandate R30 insulation—roughly nine and a half inches of batt insulation or over five inches of polyiso. For many metal buildings, this requirement alone makes tear-off impractical because there simply is not room between the purlins to accommodate that much insulation.
There is also a structural consideration that catches many contractors off guard. On a metal building with an exposed fastener panel, that existing roof is not merely a weather barrier—it is holding the building square. "You can't just remove an exposed fastener roof and put a free-floating standing seam on there," Smith warns. "You're liable to have a huge problem. You're always better off, in my opinion, if the existing roof is an existing screw-down panel that's an integral part of the structure, just to leave that in place and then retrofit."
The safety implications compound these structural concerns. Working on an existing solid deck eliminates the risk of workers falling through holes created during demolition—a particularly sobering consideration when eave heights reach thirty feet or more.
Smith's preferred approach to adding structural capacity involves the Roof Hugger system, a notched Z purlin designed to fit over the ribs of existing roof panels. The concept is elegantly simple: by attaching a new purlin on top of the existing one, you effectively increase the depth of the structural member, making it significantly stronger. What makes this solution particularly valuable is the extensive testing that now quantifies these benefits.
Roof Hugger invested heavily in base testing, including a specialized test configuration using fifty-foot runs with purlin laps in the middle—replicating how purlins actually fail in real-world conditions rather than the simplified single-span tests typically used in laboratory settings. Structural engineer Chris Moen developed modeling software based on this testing data that can predict the exact capacity increase for specific combinations of existing purlins and Roof Hugger heights.
The results have proven remarkable. On buildings with low-floating standing seam systems or screw-down panels, the Roof Hugger can add anywhere from five to fifteen pounds per square foot of additional capacity. Even on high-floating standing seam systems, where the roof panel sits an inch or more above the purlin, a sleeve system allows the Roof Hugger to achieve three to five pounds of additional capacity.
Understanding whether an existing standing seam roof is high-floating or low-floating represents one of the most critical assessments in planning a recover project. Smith emphasizes that this determination should never be delegated. "This is not something you let somebody else figure out," he states. "Something you need to figure out first while you're there is what—is this a high-floating or a low-floating standing seam."
The most reliable method involves inspecting from inside the building, measuring the distance from the back of the purlin to the bottom of the roof panel. A measurement of zero indicates a utility clip holding the panel flat. Three-eighths of an inch indicates a low-floating system typically designed for three inches of batt insulation. Anything over an inch—one inch, one and three-eighths, or one and five-eighths—indicates a high-floating system, usually identifiable by thick styrofoam spacers between the panel and purlin.
When interior access is not possible, Smith recommends drilling a test hole near the ridge, positioned close to a standing seam on the male side of the panel, directly over a purlin. The drill bit will reveal the distance before contacting the purlin.
A Pennsylvania project for a military armament manufacturer illustrates how these principles come together in practice. The facility operated twenty-four hours a day with zero tolerance for shutdown. Initial engineering analysis revealed such severe structural deficiencies that the engineer recommended against even walking on the roof, calling instead for complete tear-off with additional purlins installed between every existing purlin across the ninety-five-foot eave-to-ridge span.
This would have meant creating twenty-seven-foot-wide openings in an operating facility—an impossible situation. Smith suggested involving Roof Hugger, whose engineer analyzed the existing purlin dimensions, gauges, lap lengths, and connection details. The analysis determined that a two-and-a-half-inch Roof Hugger would add eight pounds per square foot of capacity, solving the deficiency entirely. The project proceeded with polyiso insulation infill and ice and water shield underlayment, adding a second waterproofing layer with virtually no disruption to operations.
Smith also addresses why single-ply membrane systems like EPDM create problems on metal buildings that go beyond their shorter life expectancy. Metal buildings are engineered for metal roofs that channelize water flow, providing equal loading across the structure. Smooth-surface roofs allow water to run wherever gravity takes it, typically mid-span between purlins.
While this usually causes no problems, the risk becomes acute on buildings with interior gutters at parapet walls. When scuppers replace internal gutters, they require several inches of water head to flow properly. That backed-up water can impose fifteen pounds per square foot on the first purlin alone—catastrophic loading on structures that may lack even three pounds of reserve capacity. "We've seen a number of buildings that have collapsed as a result of doing this," Smith notes.
The shift toward symmetrical standing seam panels reflects similar long-term thinking. Unlike traditional double-lock or snap panels that install in one direction and become virtually impossible to repair once mechanically seamed, symmetrical panels feature a T-shaped profile identical on both sides, joined by a cap. Individual panels can be removed from the field of the roof years after installation.
This matters because US Steel and SDI now offer fifty-year warranties on painted Galvalume, suggesting life expectancies of sixty to seventy years. "It would be nice if you could make a simple repair or modification to the roof," Smith observes, "and that's what the symmetrical panels do." Over such extended service lives, modifications, additions, or repair needs become near certainties.
The superior wind uplift capacity of symmetrical panels, achieved through continuous clips that multiply attachment points, further distinguishes them from traditional systems. Combined with installation flexibility—crews can start anywhere, skip curves, and have different workers tackling different tasks simultaneously—these advantages explain why contractors who learn the system tend to abandon double-lock panels entirely.
For building owners weighing their options, Smith offers straightforward guidance: understand that recover can be a great option when certain parameters are followed, engage qualified engineering when capacity concerns exist, and recognize that the contractor ultimately determines whether the system achieves its designed lifespan. For long-term owners, metal roofing represents the most durable path forward.