Metal roofs are everywhere in Texas: Hill Country homes, ranch houses, barndominiums, horse barns, shops, and equipment sheds. They last a long time and handle hail and wind well. But we hear two questions about them all the time. Does a metal roof attract lightning? And if it's already metal, does it still need lightning rods? Here are plain answers to both.
Does a metal roof attract lightning?
No. A metal roof doesn't make a strike more likely. Lightning tends to hit whatever is tallest and most exposed in the area, like a two-story house on a hilltop, a barn standing alone in a pasture, or a big tree next to the house. What the roof is made of doesn't change those odds. A metal roof on a low house surrounded by taller trees isn't a bigger target than a shingle roof on the same house.
There's also some good news. Metal doesn't burn, so a metal roof is less likely than wood shingles to catch fire right where lightning hits it.
So why isn't a metal roof enough?
Because a roof is only the top of the building. When lightning hits a metal roof, the current still has to get to the ground somehow. If nothing gives it a planned path, it finds its own path down through whatever conducts best: roof screws and purlins, wood framing, electrical wiring, plumbing, gas lines, or the steel posts of a barn. That's how strikes start fires inside walls and attics, crack masonry, and destroy electrical systems, even when the roof itself looks fine afterward.
Most metal roofing on homes and barns is also fairly thin sheet metal. A direct strike can melt small holes in the panels where it hits. Lightning protection standards such as NFPA 780 don't treat thin roofing panels as a substitute for air terminals, down conductors, and grounding.
In short, a metal roof is a good roof, but it isn't a lightning protection system. A system gives the current a safe path from the roof to the earth. To see how the pieces fit together, read how lightning protection systems work.
How lightning rods go on a metal roof
A system on a metal roof uses the same parts as any other system, but it's mounted and connected differently.
- Mounting without hurting the roof. On standing-seam roofs, air terminals and conductors can be attached with clamps that grip the seams, so there's no need to drill through the panels. On exposed-fastener roofs, like the R-panel and corrugated roofs common on barns and shops, mounts are attached and sealed so the roof stays watertight.
- Bonding the roof into the system. A large metal roof is a big conductor sitting right next to the lightning protection system. Bonding the roof to the system keeps everything at the same electrical level, so current doesn't jump, or side-flash, between the roof and the conductors and arc through the building.
- Using the right metal. Copper and aluminum don't mix well with some roofing. Copper touching aluminum, galvanized, or Galvalume panels, or rainwater running off copper onto them, can corrode the roof over time. On those roofs we typically use aluminum components and keep copper away from the panels.
- Down conductors and grounding. Conductors run from the roof down the outside of the building to ground rods or other grounding. In Texas, the grounding plan depends a lot on the soil, from Gulf Coast clay to Hill Country limestone and West Texas caliche.
Barns, shops, and barndominiums
Metal buildings on open land are often the tallest things around, and they're full of hay, equipment, vehicles, or a family's living space. A barndominium is a home and should be protected like one. Long metal buildings usually need several down conductors and grounding points, and steel framing and interior metal like stalls and waterers need to be bonded too. Our farm and ranch lightning protection page covers barns and outbuildings in more detail.
Switching to a metal roof? Plan the system with it
If you're replacing shingles with metal and you already have lightning rods, the system has to come off for the roof work and go back on with mounts made for metal. It's a good time to have the system checked, since conductors and connections can be damaged or left disconnected during a re-roof. See lightning rod repair and re-roof reinstallation.
On new construction, the easiest time to plan lightning protection is before the roof goes on. Coordinating with the roofer and electrician lets grounding go in early and lets conductors be routed neatly, which usually saves time and money.
Don't forget surge protection
A roof system handles a direct strike, but lightning that hits a nearby power line or tree can still send a surge through your wiring. Surge protection at the electrical panel helps protect appliances, HVAC equipment, well pumps, and electronics.
Get a free estimate
Every metal roof is a little different, from standing-seam homes to R-panel barns, so the best way to know what your building needs is to look at it. We're a family-owned business, and the Linzy family has installed lightning rods for three generations. We serve homes, farms, and businesses across Texas and Oklahoma. Call Joe at (682) 490-2850, Monday through Saturday, 7am to 7pm, or use the form below. Curious about price? Read what drives the cost of lightning protection in Texas.