Lightning conductor

[Russell griffiths]

So new house, raised seam metal roof, all 355m of it, should it have some form of lightning conductor or some form of earthing. 

 

What has everybody done, roof is only 6m high but in a fairly exposed area. 

Hoping not to explode in the next storm. 

Cheers. 

[PeterW]

Lightning conductors have to be installed by specialist contractors and the installation certified. Not something that I’d be trying myself as the conductors they used on the last big curved steel roof we did has one at each corner and is tested annually.

[Ralph]

I did wonder about this, we have quite a high standing seam roof. From what I read on some US sites there's no evidence that metal roofs attract lightening any more than other material and they are more likely to survive a strike and not go on fire.

[joe90]

Trying to think logically about this (as I know zilch about it!) are they installed and tested on certain buildings to meet certain insurance requirements?, if they are self installed as a precaution (to hopefully reduce building damage) and not done to meet insurance spec why would that be a bad thing? Can a badly installed lightning protector cause more damage than not having one? (I have had a chimney blown off by a lightning strike and blown every electrical device in that property!!!!!).

[saveasteading]

Ahh yes. 

I built about 300 steel sheds, about 30,000m2. Over 30 years.

Lightning strikes nil.

Our supplier has made 30,000 sheds around Europe. Lightning strikes that they had heard of...nil.

 

My theory is that if lightning hits your metal building then it earths through columns to bolts to ground, like a Faraday shield.

If it doesn't then it doesn't. 

Either way, no harm done.

 

BUT. When the buildings were for a local authority, they insisted on a risk assessment by a specialist...who always advised that they install protection. This was a copper strap from the bottom of a column to a spike  adjacent.

 

If you have a metal roof on a non metal building I don't anticipate any increased likelihood of the lightning choosing your building....it will head for another building with greater conductivity,  of steel, or with a lightning conductor.

 

The risk is different for hospitals and churches.  Always provide protection for them.

[JohnMo]

Metal building is a conductor from roof to ground.  A metal roof is top of a building that is generally a conductor on top of and insulator, so the risks are different

 

No ideal if it makes a real difference.  Ask your electrician he may know?

 

 

[Wil]

There’s a whole section of electrical building design dedicated to this. Based on the rolling sphere method usually but can be directly assessed for more vulnerable buildings. Always interesting designing LPS schemes for ammo dumps. Or AA missile batteries on tall buildings in South Korea.

 

It’s a whole section of risks multiplied together to give a final risk factor. If you live on top of a hill with no surrounding trees or buildings, you may be at a slightly elevated risk level. But it’s usually designed for prevention of loss of life rather than property as any direct strike is going to melt whatever conduction measures you have and probably make a big hole in the roof anyway. Check your insurance doesn’t omit it as an ‘act of god’ but I don’t think I’ve ever seen an LPS for a private resi scheme.

[saveasteading]

I tried extremely hard to find any evidence of lightning damage to a building, other than to the obvious case of old  churches.

Stone, on a hill, high tower etc. Designed to be struck.

 

Didn't find any.

 

I don't suppose anyone wants to say there is no risk.