[Q] Would a metal roof prevent a lightning strike

[Moontanman]

Would a metal roof act like a Faraday cage and prevent a lightning strike from entering a house?

[Turtle]

no. a faraday cage is a complete enclosure. i would give a source, but none i see make the specification "complete" and only refer to "enclosure" or "box". :bdayhappy_balloons:

[GAHD]

If the roof is grounded...kinda...here's a few links to give you some info.

 

HowStuffWorks "Lightning Rod"

 

http://infao5501.ag5.mpi-sb.mpg.de:8080/topx/archive?link=Wikipedia-Lip6-2/149367.xml&style

 

-lightning rods are just low-resistance paths to ground, they still get HOT from the lightning strike so I wouldn't want a sheet metal roof to take the brunt of it and risk a fire.

 

Beast idea is to install a lightning rod proper, with a fully insulated and deep-buried grounding cable.

 

For a neat side note; I seem to remember Franklin having a lightning rod in his home with an indoor spark-gap built-in so he could see the electricity flow, but I can't find the specific reference right now.

[lawcat]

No, because it is not wise; not because it can't be done.

 

First, MTM, it is the "POINT," and highest "point" for that matter, that lightning seeks. Right?

 

Second, once lightning hits the highest point on the house, then it seeks the path of least resistance to the ground. If that path is through the house, then that is where it goes. Usually, the path is simply through the exterior wall. As charge flows through the wall, the wall becomes a resistor. If the wall is made of wood, it will burn as a resistor because of the energy that it carries.

 

Now, if there is a metal roof, the charge from the lighting will go through the good conductance of the metal roofing first, but then it will find a wall again to hit it to the ground.

 

That is why long time ago people figured out that the best protection is the lightning rod. The rod provides a "point" and a straight shot to the ground, and it is inexpensive.

 

Now let's look at metal roofing. Sure, you can wrap your house in metal roofing. And you can provide a highest metal point on the roof. But then, just like for the rod, you will have provide clad connecting your metal roof to the ground. In addition, when charge moves through your metal roof, the metal roof must have the thickness to sustain the charge without excessive heating; it must not be damaged.

 

For prudential reasons, metal roofs should not be conductors because then the roof must be thicker just like the metal lightning rod, and the thickness increases the price of the roof. Why spend money on that when you can have a cheap lightning rod?

 

Roofs serve insulting function and roofs direct water. Roofs should not be designed to conduct lighning because of the risk of damage to roof's primary purpose: insulation and water protection.

[modest]

Usually, the path is simply through the exterior wall.

 

Usually :bdayhappy_balloons:

 

I agree with the posts so far. A Faraday cage is not so much a cage unless is is around you as well... like a car or an airplane. I found this:

Lightning

 

A metal roof will absolutely not increase the likelihood of lightning striking your home. However, if your home were hit by lightning, your metal roof would disperse the energy safely throughout the structure. Since metal roofing isn’t combustible or flammable, it’s a low risk and desirable roofing option where severe weather is concerned, especially for lightning.

Metal Roofing 101 Presentation – Getting an Estimate, Benefits & Value of Metal Roofing

That sounds right, but, they're trying to sell you a metal roof so what are they gonna say

 

~modest

[Moontanman]

the reason i ask is that when i was a little boy we lived in a house with a tin roof and it was struck by lightning and the lightning spread out across the roof and jumped to the ground all around the house, i was sitting on the porch when it happened and saw it jump off the sides of the porch.

[lawcat]

the reason i ask is that when i was a little boy we lived in a house with a tin roof and it was struck by lightning and the lightning spread out across the roof and jumped to the ground all around the house, i was sitting on the porch when it happened and saw it jump off the sides of the porch.

 

Interesting phenomenon. I can not tell you why with great certainty, but here is my thinking. You must have lived in a wet climate where air was saturated and provided a better path to the ground than the house itself. The charges juming all around the house stems from the fact that only one point had higher energy (where the lightning struck) and the perimeter of the roof was at the lower voltage level. So the charges would dissipate throug the roof from the point of the hit to the perimeter, and then seek air as lower resistance.

[Moontanman]

it was a wild effect, water was dripping from the roof in torrents at the time

[ricaroofers]

Lightning rod should be a best thing for you to do. The metal roof could only a conductor for the lightning. And the charge could seek a way or a path to the ground.SEO Services