Grounding a Tin Roof

skent · May 18, 2004

The house is close to 200 years old. Orig was a one floor cabin. Second floor was added in the 1890's.

the tin Roof is close to 70 years old.

I had to put new rain gutters up last weekend, and got to thinking, if the roof were to be hit by lightening, what could happen. There is no real path from the roof to ground, other than thru the house/wiring.

Would it make sense to attach a #2 copper or Alum wire to the corner of the roof and attach to a ground rod?

I don't want to do anything to attract it, but to prevent any damage.

Any advice?

_RaT_ · May 18, 2004

That lightning will find a path, after all it just traveled 30,000 feet without one. In all seriousness, I don't see why a ground would hurt, just how effective it would be in the event of a strike is anyones guess.

EastTexFrank · May 18, 2004

I can't see what it would hurt but can't see that it would help either. It would need to be some pretty stout wire to potentially handle a few million volts travelling close to the speed of light. /forums/images/graemlins/crazy.gif /forums/images/graemlins/crazy.gif /forums/images/graemlins/crazy.gif If it really worries you maybe you need some kind of lightning rod, higher than but still close to the house but then again that might just provide a target.

Inspector507 · May 18, 2004

Trained lightning protection people are worth their weight in gold. In this area all lightning protection installers must be certified by UL. The conductor they use from the rods to the ground are loose braid, multi-strand copper. I think Aluminum would melt before any benefit could be gained.
My advice would be to have someone trained do the installation for you. Rods along the ridge line AND on the chimneys.

DaveNay · May 18, 2004

For the most part, lightning arrestors do not provide a desireable path to ground for a lightning strike. They are designed to dissipate electric charge from the air around the protected structure, and prevent a lightning strike in the first place. I believe that the electrode is actually insulated from the structure, and does not provide a ground for the structure.

As Inspector507 mentioned, someone who is qualified in this respect is the best answer available.

Dave

fivestring · May 18, 2004

"The conductor they use from the rods to the ground are loose braid, multi-strand copper. I think Aluminum would melt before any benefit could be gained."

With the amount of volts, amps, watts in lightning, nothing man knows of will hold up to a strike, including multi-strand copper.

DaveNay · May 18, 2004

( With the amount of volts, amps, watts in lightning, nothing man knows of will hold up to a strike, including multi-strand copper.)

WHAAATTTT?!?!?!

/forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

You mean the little $2 "lightning trap" thingy I installed on my telephone line won't work???

/forums/images/graemlins/shocked.gif /forums/images/graemlins/shocked.gif /forums/images/graemlins/shocked.gif

Dave

skent · May 18, 2004

I found a web site that sells all the stuff

http://www.lightningarrestor.com/

good place to start

boustany · May 18, 2004

Believe it or not, a 'lightening trap' probably will work, because that sort of thing is designed to protect against the very short duration pulse induced by a 'near strike'. For example, if lightening hit a tree, the EMF generated would induce a powerfull voltage in nearby telephone or power lines which would be enough to fry most electronic gizmos. A direct strike will vaporize most any conductor.

I actually saw lightening strike a building about 50 feet away from me at the time. For some reason I was staring at a wall while wating for the rain to stop and lightening hit the part I was staring at.

It was awesome, just like a bomb went off inside the brick wall. A sci-fi death ray wouldn't have been more impressive.

'Thunder is good, thunder is impressive; but it is lightening that does the work' - Mark Twain.

SPIKER · May 18, 2004

Like someone said not much will survive the lightning strike...

The copper conductor usually will be leave a tail tale sign that there was a hit, there should be a fused link in the run near the gorund and that will blow out, and then the lightning will still let current flow, but at a reduced rate as it will use the vaporized copper that is in the air as a current path. quite impressive needless to say!

I was looking out a window durring a storm when I was 16 or so, it struck an old ELM tree about 60 yards out. I went out to take a look the next day. I WISH I had a camera back then. it took the bark off in a spiral candycane type stripes 4 of them one on each quarter. the strips were about 1" wide and 1" deep in the wood/bark. and laied out away from the tree like some one took a giant apple peeler and ran it down each quadrant of the tree and left the bark attached to the base still but the top starting pints fell back about 40 feet out and away form the tree's main trunk!

Anyhow the roof is susposed to be Insulated from the rods that way the lightning goes out around the structure... someone mentioned this above too...

Mark m /forums/images/graemlins/smile.gif

BXMMCC · May 18, 2004

Well, seems like the house hasn't been bothered by lightning for a few years, nor the roof, so why not gamble that nothing will happen for a few more?

DaveNay · May 18, 2004

( Well, seems like the house hasn't been bothered by lightning for a few years, nor the roof, so why not gamble that nothing will happen for a few more?
)

Because [insert diety of choice here] reads TBN, and has now realized that he/she/it has missed that house for the last 200 years, and there is a lot of catching up to do! /forums/images/graemlins/frown.gif /forums/images/graemlins/frown.gif /forums/images/graemlins/frown.gif

Dave

chim · May 19, 2004

Our company has done projects where the lightning protection systems were a part of our contract. We used a specialty subcontractor for the installation of all the lightning protection systems, without exception.

It looks easy enough to install, so long as you would have the correct design. One big concern is the potential to attract lightning - then not have the proper grounding path to deal with it. Having the wrong installation would likely be worse than having none at all.

And yes, they do use stranded aluminum for roof circuits and downleads. It has a weave to it (not a twist, like normal wire). Lightning rods are very sharp on the tip (to start the arc). There's a nuclear-powered lightning rod (covers an extremely large area and one will replace gobs of regular rods). Believe it or not - the first lightning protection subcontractor we used had a foreman named "Rod".................chim

fivestring · May 19, 2004

Does your company or subcontractor grant a warranty?
Guarantee that lightning will not strike the protected item?
Guarantee that if lightning does strike the protected item that it (and all contents and attachments) will be replaced by your company or subs?

Lightning and moving water (streams, rivers, freezing water) are the two biggest forces we know of.
Hard to stop either one.
Just ask folks that get flooded out by OLD MUDDY.

chim · May 19, 2004

On the projects I've been involved with, there were no warranties covering subsequent lightning damage. We have used two different reputable firms as subcontractors. At the completion of their work, the work was inspected and a "Master Label" was provided certifying the work was done properly.

I wasn't joking about nuclear-powered lightning rods. I think they went by the name "ellipsoid". They contain a small amount of radioactive material that is supposed to enhance the ionization of the air and have the cloud discharge before it has a chance to build into a damaging strike.

People from both subcontractors and at least one electrical engineer told me that although we have effective lightning protection systems, there was still a lot that is not fully understood about lightning.

reb · May 20, 2004

About 30 years ago a neighbor's house was hit by lightning and burned to the ground. As an electrical engineer and a confirmed diy-er, I figured I could install some kind of lightning protection system on my house. After a bit of research I concluded there was probably not enough scientific knowledge for a fool-proof system and whatever I did might be viewed by an insurance company as contributing to the problem if my house were hit. Therefore, I just cross my fingers during a storm. This is an area where I would go to a pro if I wanted to try something.

cisco · May 20, 2004

My contractor is about 80% through building a garage / apartment on my country property (30 X 42 ft, 2 story, 35 feet high, with 2 nine foot high doors for my tractor and boat bays). Such will have a coated aluminum roof, and the lightening protection stuff seems reasonable (done by a lightening protection subcontractor). There are rods along the apex of the roof every 6 feet or so, connected to each other in the attic with what appears to be 3/4" thick and loosely braided copper wiring. The wiring connects to grounds (8 foot in ground stakes) on each end of the dwelling, with the copper wire inside conduits going down those 2 sides of the dwelling. What else - hmm - surge arrestors on the main electrical line in and on the phone line. Despite all of the above, I will have lightening damage insurance, along with usual flood, etc. - I, like prior posts, may think the system, installed by professionals, will work, but I'm not certain, and I've seen what a lightening strike can do to a house.

Logan · May 20, 2004

Lightning seems to have a mind of its own and does what it wants when it hits. I had it hit a pine tree that was about ten feet from a shallow well that is about twenty feet from the house. It followed a tree root to the well and came into the house through the wiring, didn't hurt the well nor another, my deep well, on the same line. It came into the panel box in a closet four feet from where I was sitting at this computer. It knocked out a 13" TV in my daughter's room, got the microwave in the kitchen, and killed one of the two garage door openers and caused an ugly stain in my computer chair. It didn't make a mark on the well house or my home.

SPIKER · May 21, 2004

yep it will cause many a ugly stain on the carpet floor chair or any place a person may be standing at the time!.

We had one heck of a lightning storm last night and today too.!

last year this time my sisters house was nearly burnt down cause of it . when it hit it burnt the house 2 up from here (its replaced now with new construction) and burnt out her wiring panel and phones. she was lucky to be home and got the fire dept there soon enough to stop hers form going up!. though she also needed to call the carpet cleaners too! lol

her hubby hosed it down with a dry chemical extingusher and put it out before the got ther, but flames were already comming out the ves of the neibors house... the hosue between them not a scratch! (sity lots of aobut 80 feet or so wide.)

Mark M /forums/images/graemlins/confused.gif

To20Chris · May 23, 2004

The individual pans in a standing seam roof are not all that well connected to each other electrically, especially after 70yrs! You would have to bond a ground conductor to each pan in order to make it effective. It has to be a really low resistance path (hence the low-inductance weave in the conductors) or it is not much good. Also, the roof is probably tern (tin coated steel), so you would have a hard time bonding anything to it that would not corrode after a few years (dissimilar metals). Go out and fine some really cool old lightning rods (the kinds with the glass spheres in them), and have someone put them up right. Or forget about it - you've got a much better chance of getting hurt on the way to work!