Should I ground a new metal roof?

Just recently someone was asking about grounding a new metal weather vane on a building on this site. That got me thinking about whether I should attach my old copper lightning rod cables to my new metal roof. The two story house had lightning rods on each of the three gable ends and at least one in the middle. Contractor would have put them back up but you end up putting holes in a new roof and the house looks more modern without them. They weren't in the best of shape after they came off of the existing roof anyway. He offered to run the copper lightning rod cables up under the tin in a channel and then run some screws through the tin and cable. I told him I would think about it and could do it myself. What is everyone doing inregards to lightning protection with a metal roof???

I can not say for sure either way but of all my buildings with metal roofs only 2 do not have the roof grounded. I do not think it really matters since over the years you see old barns with metal roofs and they are not grounded and there still standing

If only the roof is metal ?????If The roof is metal and the sides are metal and toughing the ground then you have to make sure the roof is grounded to the side. If not you can get an ark between the two right at the rafters.

I believe they do two things, they can bleed off ground charges into the air through the points of the rods, and second if struck, they bleed the energy away from the structure through the woven cable, to the earth rod. I have them, I have seen lightning in my home, in a house trailer, and on a cyclone Fence I was about to touch. (The spark from the last one mentioned only jumped a foot to my hand) Do it. Jim
Texas A&M opinion

I have the same question? Also what about my shingled house? It has asphalt shingles. There is 4 lighting rods on top and I think they look dumb as he!!. I want to remove them but then I wonder if I should. Every new house built doesn't have them. Your opinions welcome.

Read my post below to this thread. Jim

I have lightning rods on my house and barn, they were there when we bough the place and we had the roofer put them back after reroofing. He didn't unhook the copper cables and they still run to ground. The rods themselves are pretty neat with purple glass globes in the middle.

I can't say about rods per-say, but would make sure it is grounded. I have a metal roof on a wood barn with 8' shop lights. I got caught in a storm and sheltered in the barn. Every few mins I would hear a crackling then a pop and flash like a picture was taken. Turned out it was static discharge from the tin to the grounded lights. It was jumping 18" from the roof to the lights. And yes the roof is bonded to ground now.......

That's a tough question.

My eyes see a lightning bolt come from the sky and zap something. But, since voltage is constant (sky) and current flows from the more negative (ground) to the more positive (sky), lightning strikes actually flow from the ground to the sky. I guess that's why people that have been struck by lightning that live to tell about it, say that they could feel something passing through their bodies before the neighbors saw them get zapped.

In theory, the taller the lightning rod, the shorter the distance current has to travel from ground to the voltage source (sky), so the increased chances of being ground zero for a lightning strike. Kind of like standing barefoot in a farm field that goes on forever and ever with no trees for miles and miles, and being the tallest thing during a storm...the lightning rod by default.

My suggestion is to ground your roof, and then to convince your neighbor to buy and put up the tallest flag pole that he can find. Sure, the bangs of close lightning strikes will wake you up in the middle of the night, but your neighbor on the other hand, will be tossed out of bed to your good fortune. If your neighbor asks why he should put up a really tall flag pole, tell him its his patriotic duty, and then walk away while pointing at him and whistling Yankee Doodle or something.

Good luck.

Mark

I read the article and surely not an expert, much less spending 35 years of my life studying the subject.

I have been told that rods were intended only to bleed off the static charge built up when clouds move through the atmosphere generating "static electricity"....like you do walking across a carpeted floor especially in the winter with cool dry air. You realize that when you grab a door handle and get a spark, or you have plastic seat covers in your truck, slide across the seat to grab the door knob and get whacked.

I believe the bleed off theory having made a career out of managing high voltage and understanding it's behavior, ozone generation and the physics of all of that.

However, the amperage of the bolt is what deters me from considering rods effectiveness for a direct strike. You can look up the fusing current of conductors as compared to normal loads and for a conductor to sustain a bolt of lighting at 35,000 amperes, much less 158,000, without fusing and blowing apart (hence become useless after it attracted the lighting in the first place) it would have to be a foot in diameter or something of the sort. Most lightening wires I have seen are like 1" across, square in shape and spiraled....for whatever that does.

I have seen them spiked (spire) and the ones with the glass bulb between the spire and the ground connection. Have no idea as to to the reason for the bulb.

Have a pecan tree about 50' from the house and 20 feet from a Morton building that sustained a hit one night. Trunk was about a foot in diameter at the time. Was in bed and the fireball lit up whole house, an enormous boom, and scared us big time. The next morning I examined the tree and it had a burn mark from the top to the bottom.

On the trunk it was about 4" wide, bark blown off and burned into the tree about 1". The tree survived but the core wood rotted. It grew new bark around the dead part and it is alive today some 20 years later. with the trunk about 18" in diameter now. It is however on it's last leg. I bought this place in '79 and it was a mature tree then. Just time for it to go I guess. The lightening didn't help matters obviously.

Mark

It seems you asked if you should ground your metal roof but some answers were more to whether or not LIGHTNING RODS should be used. Its been years since I was concerned with lightning protection so take this with a grain of salt. Id say since you have a metal roof, lightning protection is more warranted then if it were a conventional plywood n shingle roof. However, I don"t see simply grounding the roof as any substitute for a true properly designed and installed lightning protection system. Go ahead and ground it if you please, but if you do so Id suggest (if it also has metal sides) to bond the entire outer structure as a sort of protective shell/skin like if you were sitting inside your automobile shell. However, I don"t see nails or screws as the best bonding method (sure, that and them laying on each other is still an electrical bond) i.e. you would almost have to run the wire and bond to each n every sheet of roofing and siding for a better more complete grounding bond.

Either install a real lightning protection system or else do nothing, but if you insist I don"t see any harm in trying to ground the buildings outer metallic skin/shell, that could??? (But NO Warranty) help if you were inside and the roof had a lightning strike, and if it was also bonded to the electrical services safety equipment ground system, such could provide a path for fault current return to trip a breaker and de energize a faulty circuit.

Whewwwwwwwwww lol

John T NOT any lightning protection expert

Around here in central NY., it depends on the code jurisdiction that you are in. As a contractor it got confusing, and I learned to call code enforcement where I was working. We erected an all steel comercial building and the inspector wanted the roof sections strapped to the sidewalls and several propper ground rods, even though the whole building was steel and every screw made a connection to the red iron frame. He said the gaskets insulated the Tech screws(???) We just did what he wanted.
Loren, the Acg.

Heard once that the glass bulb on the lighting rod would explode if the rod took a hit. That way you would know the rod was hit. Don't know how true it is but, that's what I heard.

My brother in law had his wooden barn with a steel roof redone by a contractor, and had the lightening rods done at the ame time, shortly after lightening struck it and it burned down, fast. He asked the insurance inspector why it happened with new rods on it, He was told that the lightneing bolt has more power then a rod can handle.

Ok, question to those that say he should bond his steel roof to ground, how does one hook up roof tin to a ground wire?

According to the National Electrical Code you DO NOT have to bond tin, there is no good way to connect a wire to it. Now if this is a steel FRAME building then yes, you must bond to the steel structure.

How many on here have aluminum or steel siding, did you bond the siding to ground?

I would not ground it, no sense attracting the lightning without a good suppression system.

"Ok, question to those that say he should bond his steel roof to ground, how does one hook up roof tin to a ground wire? "

EXACTLY that's what I was talking about when I mentioned a proper bond to each n every piece of sheet metal. That's a lot or work. True the physical contact and screws or nails provides some degree of electrical contact, but that's NOTHING compared to a single piece of metal having a proper connection.

Oh well, its his choice right or wrong lol

John T

Ever wonder why the tallest tree in the yard get the hit. Then why make your house that tall tree. Want to protect your house plane tall pines or firs about 100 ft away from it.
I have some pics of lighting going from cloud to cloud across the big valley in CA. It's about 20 miles across and you would not want to be anywhere near it. I will look to see where they today.
Walt
PS I shed my neighbor why he had a loop in the cable from the Satelite he said because lighting can't travel around corners. hmmmmmmm

Some years ago, I moved into a home that was roofed with Reynolds aluminum. It looked like cedar shake, from a distance.
I had Cotton States insurance with the home I sold but they would not insure this home unless I installed a grounding system.
I changed Insurance companies and they said nothing about the metal roof?
I would check with your insurance company and see what they say.

Well somebody put it on there for a reason. Realizing that the rods I have seen were on late 1800's houses, 2 story T shaped, 16' wide max on the joists , usually 2 story, full size timber 2x whatever was a full 2x whatever, flat nails, tin roofs and all.

I bought one around 1980 for $250 to dismantle and remove from the property. Plan was to get some building materials to build out buildings on my soon to be farm...vacant land at the time, and I thought this was the answer.......WRONGGGGGGGGGGGG. What a waste of money, time and the efforts of my family trying to make something out of nothing. But I had a dream, no money and we did the best we could....but we made it work and I am still living on the homestead.

I didn't know glass could settle, but the glass in the window panes had turned yellow and had settled to the point that there was about a 1/2 gap between the pane and the top of the frame where it once occupied.

Mark

Lightning (full solid hit struck our garage. there was a lamp housing in the rafters (I made it from sheet metal to shine on the BB hoop) it was connected by MN 14-2romex with ground. The strike blew the tin lamp to vapor. Put a 30 inch hole in the roof, and striped the copper clean and shiny (no loss of size just no insulation) jumped into the garage wiring from 10 inches away, leaving the plug copper blades screwed to the wire ends. Stripped the wire bare.
Attacked a roller chain come along welding the rollers together .750 pitch! Then blue cone shaped holes in the garage concrete where the rebar crossed the mesh, then jumped into an extension cord following it to the house (only copper remaining) till it found a circuit in a bedroom and blew insulation off of that circuit till it got to the breakers. It blue the breaker out of the panel, and went to ground at the ground buss in the box. I have no doubt that the heavy copper cable on the rod system I have (equal to about #0 wire in cross section) will do the job. Jim