With this beautiful weather across the country it sounds like you all need some work related stimulation so here it is. You helped me once before but this time it’s on my own home.
I can’t find much info on lightning strikes. Specifically, the path the lightning strike takes. Here is my situation. Your opinions are greatly appreciated. I apologize for the length but felt you are detail oriented people and would want to see it all.
My two story, Santa Fe style, stucco house was struck by lightning. The stucco and wire mesh runs up the wall, has a stucco cap, then down the inside of the wall to the roof. We travel a lot and we were not home when it happened so I can't tell exactly when it occurred. I've narrowed down the times we were traveling but it’s also possible that we were struck when we were away from the house for a few hours.
I discovered the damage when I went up on the roof to service my evaporative cooler for the season (I'm in AZ). The stucco looked like it was pushed up from below and in some places you could open it up like one of those old, metal lunch boxes with the hinged lid. I was at a loss as to what happened but a storm was coming so I started patching and putting on tarps. Some of the cap was so bad that 4 to 6 feet of it had to be removed. My son and I patched the worst places and caulked the rest. I figured I would have to make an expensive, permanent repair later so this was enough until I could do the major work. We went to the upper level and did the same thing. I was running a bead of caulk following a crack when I saw a dime sized hole over the side at a 45 degree angle. It looked like someone had taken a cutting torch to it! Only then did I take out my camera, after the majority of repairs had been made.
My adjuster was swamped up north so he sent out a construction investigator and I just read his report. The investigator admitted he didn't know that much about lightning strikes. He said he had spent a few hours on the internet researching before he came over. I also consulted the Fire Marshall and Fire Chief and everyone agrees that the house was struck, the dispute is the path it took to ground. The investigator says the lightning path took the shortest distance and it probably went straight down and came out below grade, directly below the strike. He says the other damage is consistent with the age of the building (1998). He also claims that the bolt could have followed a metal down spout (4’ away) even though it terminates in a PVC pipe 12” above grade.
I agree that the lightning took the shortest path but shortest path with lightning is not a linear measurement, shortest path is the path of least electrical resistance and it can be much, much further away. I say it struck at the high point and followed the wire a quarter way around the house (140') to where the wire contacts my frost free hose bib which is directly connected to my underground, 1" copper water service. I think my wire mesh acted like a faraday cage and my water line was the only ground. I also claim that, since stucco is not impervious, that some moisture was under the stucco. This water flashed to super heated steam and blew my cap off.
In the vast majority of cases cloud to ground lightning doesn’t strike the ground, it goes from the ground up. When a strike starts it sends stepped leaders down from the clouds. They leap forward in spurts 150 feet at a time following a zigzag path that has the least impedance or resistance and best continuity. When it gets within 100 to 300 feet of the ground, the charge in the ground gathers streamers together from all points until the charges connect and complete the circuit, then a return stroke lets loose and leaps up that completed circuit. I think my many wires close to the ground acted like conduits for the streamers and each carried some of the trickle charge but my 1” copper line carried the majority. That 1” line was also large enough that it could carry the load where a smaller line would have simply burned out like an overloaded fuse. My electrical, HVAC, gas, phone, cable and plumbing (with the exception of the hose bib) are isolated and they do not touch the wire mesh. Since there was no contact, there was no continuity, which means no streamers, so no lightning and therefore no damage to these systems.
Other facts to consider;
Directly below the strike I had an old TV that I bought from a motel for $25. One day it didn’t work so I figured it died and I threw it away. Also, when we upgraded our internet a few months later the installer found there was too much noise on that same coax cable so we had to replace it. It had continuity so it didn’t blow apart; it just had a weak signal. This was all before I saw the roof and I am not making this part of the claim, it’s just for information.
Stucco is just a cement product and does not conduct electricity. My house also does not have an exposed metal weep screen. My stucco terminates below grade and the wire is encased in stucco and does not come in contact with the ground.
Nothing else was damaged. No electrical, no signs of scorching or arcing, no electronics, no in-floor heat, no copper plumbing. All the above are 28 feet directly below the strike point but were un-touched. An HVAC roof top unit is 10’ away and is 6” higher than the strike point. The metal chimney is 25’ away and 6’ lower. A large tree 35’ away is 2’ lower. The hill and house 300’ away are higher. All un-touched.
I visit the roof at least twice a year. Once in the winter to put up and take down Christmas lights and once in the spring to service the cooler and caulk the spider cracks on the stucco. I know the conditions on the roof. For you that don’t know stucco, this caulking is a yearly chore. We re- painted the house in 8-03, serviced the cooler 5-04, Christmas lights 12-04, service the cooler again 5-05. In all those times there was nothing out of the ordinary. Then our 1st grandchild was born so we were all over the country following her (my daughter has a unique job) and I didn’t put up Christmas lights that year. I discovered the damage 4-6-06.
From my point of view, the biggest part of the claim will be because of the secondary damage where water got in the walls because of the cap being open. The walls below the damaged parapet face east and south and all show signs of distress and, in my opinion, there is a good chance for mold being present. The sun here in Arizona is very intense. Only this 140’ of parapet was damaged, the remaining 270’ is normal and the north and west walls are in like new condition.
We all agree the house was struck. The lightning had to go somewhere. There are no signs of lightning hitting anything else. My claim is the only one that fits the facts and the field observations.
I am trying to gather information to prove my case. Please comment or ask any questions or steer me anywhere I can find more information.