Latest / Internet of Things with Fexingo: Connected Devices, Sensors, and Industrial IoT / How IoT Sensors Are Preventing Roof Collapses on Big Box Stores
Transcript
- Luna: You know, every time I pull into a Home Depot parking lot, I look up at that massive roof and think — what's holding this thing up? Lucas: Right — it's an enormous single-span structure. Most big-box stores and distribution centers have roofs that cover anywhere from 80,000 to over 200,000 square feet. And the load on that roof changes constantly: snow in the winter, rain ponding, even the weight of HVAC units and solar panels that get added later. Luna: And we've seen what happens when it fails. The 2020 roof collapse at a Family Dollar in Illinois? That killed one person. Or the 2023 collapse at a lumber yard in Pennsylvania. Lucas: Exactly. Those events are rare, but when they happen, it's catastrophic. And the thing is — we have the sensor technology to predict these failures weeks or even months in advance. Today I want to talk about a specific installation at a 150,000-square-foot distribution center outside Chicago. They retrofitted the roof with a network of strain gauges, tilt sensors, and environmental monitors. And during the winter of 2025, that system flagged a dangerous snow-load imbalance that would have been invisible to the naked eye. Luna: Huh. So the roof looked fine from above, but the sensors caught something wrong underneath. Lucas: Exactly. The building had a slight slope — maybe one degree of tilt over the entire span. That's normal, within spec. But when a heavy snow fell and then partially thawed and refroze into ice, water migrated to the low side. The sensors picked up a 40 percent increase in strain on four trusses near the south wall. The facility manager was able to bring in a crew to shovel off that section and redistribute the snow before anything gave way. Luna: I love that this is a concrete example. How much did the sensor retrofit cost? Lucas: Around $85,000 for the full system — including installation, the wireless gateways, and a three-year data subscription. The facility's own maintenance team installed the sensors in about two days. Compare that to a roof replacement, which can run half a million or more, or a collapse that could shut down operations for months. Luna: And it saved them from a collapse. That's a no-brainer ROI. Lucas: Yeah, and if today's conversation gave you something useful — a new angle on how IoT is quietly making the spaces we use every day safer — that's exactly what this show is about. The way we keep these episodes ad-free and focused on the substance is through listener support. If you value that, you can contribute at buy me a coffee dot com slash fexingo. Luna: It's a small way to keep the show going, and every bit helps. Lucas: So back to that distribution center. The system they used is built around three types of sensors. First, strain gauges bonded directly to the steel trusses. Those measure micro-deformations in the metal. Second, tilt meters at several points on the roof deck. And third, a weather station on the roof measuring snow depth, temperature, and wind. All of that data feeds into a cloud dashboard that alerts the facility manager when any reading crosses a threshold. Luna: What thresholds are we talking about? Like, at what number do you get a text message? Lucas: Great question. The strain gauges are set with a baseline from when they were installed — that's the 'zero load' reading. Then the system tracks changes. A 15 percent increase in strain triggers a yellow alert, which means 'check the roof visually.' A 30 percent increase triggers a red alert, which means 'take action immediately.' The tilt meters have a similar approach: anything beyond 0.5 degrees of tilt from baseline warrants investigation. Luna: And these thresholds were tuned for this specific building's design, right? Lucas: Exactly. Every roof is engineered with a specific load capacity. The sensors need to be calibrated to that building's structural analysis. The company that installed this system — they're a structural engineering firm that moved into IoT as a service — they start with the original blueprints and load calculations. Then they place sensors strategically, not randomly. Luna: So it's not a one-size-fits-all product. You actually need engineering expertise to deploy it. Lucas: Right. And that's actually a barrier to wider adoption. There are maybe a dozen firms in the US that offer this as a turnkey service. Most building owners don't know they need it until after a near-miss or a collapse in their region. Luna: Speaking of near-misses — that distribution center in Chicago, did they have any other events beyond that snow imbalance? Lucas: Yes, actually. In the spring of 2026, the system flagged a different issue. A large HVAC unit on the roof had been installed a few years ago, and over time, the vibration from the unit had loosened several bolts on a truss connection. The tilt meter near that unit showed a gradual, creeping change over about six weeks. The maintenance team found the loose bolts, tightened them, and the sensor reading returned to normal. Luna: So the system caught something that had nothing to do with weather. That's really valuable for ongoing maintenance, not just emergencies. Lucas: Exactly. That's the long-term value proposition. These sensors can catch fastener fatigue, corrosion-weakening of steel, even the effects of nearby construction vibrations. And because the data is continuous, you can see trends that a quarterly visual inspection would miss. Luna: What about cost? You mentioned $85,000 for the retrofit. Is that typical? Lucas: It depends on the size and complexity of the roof. For that 150,000-square-foot building, it breaks down to about 57 cents per square foot. For a new building, you can integrate sensors during construction for even less — maybe 30 to 40 cents per square foot, because you're not doing retroactive wiring and mounting. Some of the newer systems are fully wireless, using low-power wide-area networks like LoRaWAN, so no trenching or conduit needed. Luna: And how many big-box stores and warehouses are out there? This can't be a tiny market. Lucas: It's enormous. In the US alone, there are roughly 40,000 big-box retail stores and over 18,000 warehouses and distribution centers over 100,000 square feet. If even 10 percent of those adopted roof monitoring, that's a market worth over $300 million in sensor hardware and services. Luna: Why hasn't adoption been faster? Is it just awareness? Lucas: Awareness is part of it. But there are two bigger factors. One: building owners often assume their insurance will cover a collapse. And it does — but insurance doesn't cover the business interruption, the reputational damage, or the human cost. Two: many owners think their roof is fine because it's 'only' 15 years old. But roofs age differently depending on climate, maintenance, and modifications like adding solar panels. Luna: And solar panels — that's a growing concern, right? Adding weight to a roof that wasn't designed for it. Lucas: Absolutely. Every solar installation adds about 3 to 5 pounds per square foot. On a 150,000-square-foot roof, that's up to 750,000 pounds of additional load. Most structural assessments are done at the time of installation, but they rarely account for future snow loads on top of the panels. And the panels themselves can create uneven snow distribution — snow slides off one section and piles up on another. Luna: So the sensor system is almost a requirement for any building that adds solar. Lucas: I'd argue yes. And a few states are starting to consider it. After a roof collapse at a big-box store in New Jersey in 2024, there was a push for mandatory structural monitoring on any commercial building over 100,000 square feet. It didn't pass, but it's been reintroduced this year. If that kind of regulation spreads, you'll see a huge acceleration in adoption. Luna: I'm curious about the technology itself. How do strain gauges actually work in this context? Lucas: It's a classic principle. A strain gauge is essentially a very thin wire that changes electrical resistance as it stretches or compresses. Bond it to the steel truss with a special epoxy, and you get a real-time reading of the strain at that point. The gauge itself costs maybe $10 to $20, but the readout electronics and wireless transmitter add cost. Then you need the data aggregation and analytics platform on top. Luna: And the tilt sensors — they're basically just accelerometers, right? Lucas: Yep, MEMS accelerometers — the same kind in your smartphone. But these are industrial-grade, with higher precision and stability over temperature changes. They can detect a tilt of 0.01 degrees. Over a 500-foot roof span, that's a vertical displacement of less than an inch. Luna: That's impressive. Okay, so let's talk about the data side. Who actually looks at this data? Is it the facility manager, or do they hire a third party? Lucas: In most cases, the monitoring firm provides a dashboard and alerts. The facility manager gets the text messages and emails. But for deeper analysis, the firm's structural engineers review the data — often monthly or after significant weather events. They produce a report that says, 'Everything is within normal parameters' or 'We recommend a visual inspection of trusses 14 through 18.' It's a service model, not just a software sale. Luna: So it's really an engineering service that happens to use IoT as the data source. Lucas: That's exactly the right framing. The sensor is the tool, but the value is in the interpretation. And that's why you see a lot of traditional structural engineering firms moving into this space rather than pure tech startups. They already have the domain expertise and the client relationships. Luna: Are there any competitors doing this differently? Like using computer vision instead of strain gauges? Lucas: There is some work using cameras and laser scanning to detect roof deflection. But those are periodic — you take a scan once a month or after a storm. They don't give you continuous, real-time data. The advantage of strain gauges and tilt sensors is that you can see a slow creep over days or weeks, which is exactly the pattern of a structural problem developing. Luna: That makes sense. A camera might miss a 0.1 degree tilt change. But a tilt sensor would catch it. Lucas: Right. And in the case of that Chicago distribution center, the snow imbalance built up over about 48 hours. A weekly scan could have missed it entirely. Luna: So what's next for this technology? Do you see it expanding to smaller buildings, like commercial strip malls? Lucas: The economics get harder. For a 20,000-square-foot strip mall, the fixed costs of the engineering assessment and gateway installation are similar, but the sensor count might only be eight or ten units. The per square foot cost jumps to $1.50 or more. That's harder to justify unless the building has a history of issues. But for any single-story structure with a large roof span, the math works. Luna: And for new construction, it's a no-brainer to include sensors during the build. Lucas: Especially with the push toward net-zero buildings and rooftop solar. If you're already engineering the roof for solar loads, adding a sensor network is a small incremental cost. Some architects are now specifying these systems in their standard designs. I think within five years, any new distribution center over 100,000 square feet will have some form of structural monitoring built in. Luna: It feels like one of those things that will seem obvious in hindsight — like smoke detectors. Lucas: Exactly. Smoke detectors don't prevent fires, but they give you time to act. These sensors don't prevent roof collapses, but they give you the data to prevent disaster. And in the IoT world, that's the real win — not just collecting data, but using it to save lives and money.