Clear-Span Metal Panels and Their Seams
Many hangars and aviation shops are covered in long metal panels over a steel frame, because the span between supports is great and the roof has to be light. Panels that run the full length of a slope move with heat, and the seams, clips and fasteners that hold them take that movement every day. A standing seam metal roof accommodates the movement on its clips, hides its fasteners and sheds water well, which is why it suits large aviation buildings.
On older hangars where the panels are sound but leaking, a retrofit over the existing roof avoids a long period with the building open. We check the structure for the added load, inspect the purlins for rust and plan the new system so the old roof stays in place until the new one is closed. Penetrations for exhaust, skylights and ventilation each get a flashed curb, and we solder or seal every sheet metal joint so a lap does not become a path.
Flame-Free Work Beside Aircraft and Fuel
Aircraft, fuel and open flame do not belong in the same building, and the roofing method follows that rule. We use mechanically attached, adhered or welded systems that do not require torches or hot asphalt, and we agree with the facility manager on a hot work policy before a single tool comes out. Fire watch, extinguishers and the location of fuel, paint and solvent storage are reviewed during the pre-job walk.
Loose debris is the other hazard. A dropped screw or a clipped piece of trim on the ramp can damage an aircraft or an engine, so we sweep with magnets, control cuttings and stage material in a container away from the flight line. Work on a building with a suppression system also means protecting the piping and sprinkler heads that hang from the roof structure. The planning for hangars on a base follows the same lines as military hangar roofing, with escort and access procedures added.
Santa Ana Gusts, Heat and Fire-Zone Rules
Santa Ana gusts of 60 to 80 mph were widely forecast for the foothills in the days before the Eaton Fire, with isolated gusts of 80 to 100 mph. A hangar roof with a large door opening is the building that wind tests hardest, because pressure builds inside the building when the doors are open. We pay particular attention to the first few feet of panel along every edge and to the ridge cap, and we write the attachment pattern for the wind exposure of the site.
Heat matters as well. The recorded high of 113 F in June bakes dark metal and loosens sealants, and a reflective finish that meets the aged reflectance and emittance values in the 2025 California Energy Code lowers the temperature inside a hangar that has no air conditioning. In a Very High Fire Hazard Severity Zone, replacing more than half a roof in a year requires a Class A assembly with ember-resistant vents.
Inspections That Respect the Ramp
Hangars sit where aircraft move, and walking a roof next to an active ramp takes planning. A drone roof inspection lets us photograph panel laps, trim and fasteners across a long roof without putting a crew on the slope, and an infrared pass can show wet insulation under a low-slope section such as an office wing or shop addition.
The area around Pasadena has airports of several sizes. San Gabriel Valley Airport in El Monte provides general aviation service, Hollywood Burbank Airport in Burbank handled 6.2 million passengers in 2025, and the technology corridor in Monrovia includes AeroVironment. Before the winter rains, we record edge fasteners, drains and flashing, then compare them to the previous visit so a change is easy to see. Many hangars share a trait with warehouse roofing: a vast, unbroken roof whose small failures hide until water reaches the floor.
Commercial Roofing Questions
What makes a hangar roof more exposed to wind than other commercial buildings?
The large door opening. When the doors are open, wind pressure builds inside the building and pushes upward on the roof from below while it pulls from above. The edge zone and the ridge take the greatest load, so we use heavier cleats, closer fastener spacing and formed trim made for that edge.
Can a hangar be reroofed without moving the aircraft or shutting the building?
Often it can, if the work is staged in sections and each section is closed before the shift ends. A metal retrofit over the existing panels keeps the old roof in place until the new one is watertight. Aircraft that cannot be moved are covered and the area below is protected from debris.
Are torches ever acceptable on an aviation building?
Not as a general rule. Fuel, solvents and aircraft make open flame a serious risk, and many facilities forbid hot work entirely or require a written permit and a fire watch. Mechanically attached, adhered or welded systems and standing seam metal meet the need without it.
How do you keep fasteners and trimmings off the flight line during roofing?
Sweeping with magnets at the end of every shift and cutting trim at a station away from the ramp are the basics. We stage material in a closed container, control wind-blown scraps with weights and screens, and walk the perimeter before the crew leaves. The facility manager signs off on the clean-up before aircraft move.
What decides whether a hangar needs a retrofit or full replacement?
The condition of the purlins and the old panels decides it. If the framing is sound and the panels are only leaking at laps and fasteners, a retrofit keeps the building in service. Rust through the panels or a damaged frame points to replacement, and we check the underside before advising.
