Metal roofs are constructed of an alloy of metals, and therefore are capable of conducting electricity, if a metal roof is in direct contact with a source that generates electricity, you could feel a mild electric shock, depending on the intensity or electrical power of the source of contact.
It is difficult to get electrocuted by a metal roof unless a massive amount of electricity is in direct contact with the roof, and that is very unlikely.
And if you are thinking that metal roofs attract electricity, no, that is a myth, metal, by its properties as a material conducts electricity well, but does not attract it.
In the following paragraphs, I explain how a metal roof behaves when it is struck by lightning.
It is possible that you may experience problems with a metal roof that is electrified, but not exactly by a lightning strike.
When a metal roof is in direct contact with a source of electric current, the roof would manage to disperse the energy evenly throughout the structure so that if someone touches it, an electric shock would be felt that would be mild but not strong enough to electrocute a person.
I say all this from my own experience, in one of my first villa constructions where I used a metal roof, one of the parts of the roof was so low that you could reach it with your hand, someone told me that the metal roof was electrified, although a mild electric shock was felt, this could be a danger in case of rainy days.
What caused the problem was an electrical wire that was punctured by one of the screws in the metal roof, the contractor who installed the roof was not careful, the electricity was distributed all over the metal roof, but this can also pose other problems and fire hazards.
So what should be done to avoid this type of problem? What solutions and safety measures should be taken into account with a metal roof?
Why is your metal roof electrified and how to avoid it?
Well, if this happened to me it can happen to anyone else, when a metal roof is electrified it is a big uncertainty, but in my opinion, in 80% of the cases, it is due to some perforated electrical wiring making direct contact with the roof.
To avoid this type of problem the first thing you should do is to make sure that the people or contractors that are doing the installations in your house are professionals and know what they are doing (my problem was due to a bad installation of the metal roof).
In case it is not a construction problem, seek advice from an electrician, but first make a visual inspection of the roof from both the exterior and interior and look at all the elements that require an electrical connection that could be making contact in some way with the metal roof.
The electrician should verify that there are no problems with any grounded conductors touching the metal roof.
Does the metal roof need to be grounded?
Metal roofs in residential settings do not need to be grounded, there are currently no building codes that recommend homeowners to ground metal roofs because metal roofs are actually quite safe in and of themselves.
Grounding is the deliberate earth connection by means of a set of materials that conduct current with a low enough impedance to prevent the existence of voltages that might put people at risk.
In layman’s terms, grounding is a means of quickly redirecting a sudden, excessive buildup of electricity to the ground, in the specific case of metal roofs, to a potential lightning strike.
In a residence, grounding is formed by a system of naked copper wires that are wired to each metal electrical box in the house. Its purpose is for the current to be dispersed, so in a manner of speaking. The exact same concept can be applied to a metallic roofing system.
As a safety precaution, if you have a metal roof, see that the vent pipes that pierce it are made of plastic, and you can also have a large wire or metal strap leading directly (without sharp bends) to a ground rod. Once the electricity finds the easy path to the ground, it will follow that route.
A metal roof should only be grounded if a lightning protection system is available.
In the case of large and tall buildings, where The metal roof functions as part of the lightning protection system, when it comes to the exposed components, i.e. ridge, eaves, and ridge, All parts of the roof, such as a ridge, eaves, and dormers, must be connected to each other and grounded.
How does a metal roof behave when receiving an electric shock?
Although metal is a material that conducts electricity very well, in reality, a metal roof when receiving a lightning-like electrical discharge behaves the same as any other roofing material, with the exception that a metal roof is a non-combustible material (it does not catch fire).
If lightning strikes a metal roof structure directly, it will suffer physical damage and disintegrate at the point where the lightning strikes, just like any other material.
On the other hand, if lightning strikes a metal roof indirectly, the electricity will quickly discharge through the entire roof structure without harming the occupants of the house.
Remember that electricity will seek the fastest way to reach the ground, so it will travel by any contact path to reach the earth, so it is recommended to avoid showers and wired appliances during thunderstorms.
But this recommendation is in general, not specifically for homes with metal roofs.
How to avoid electric shocks on a metal roof?
As I mentioned at the beginning of the topic and my experience with an electrified metal ceiling, to avoid this you must do conscious work when you have electrical elements that make contact with the metal ceiling, such as electrical wires, remember that the screws are metal also and can pierce any wire and produce a metal roof that when touched makes you feel electrical shocks.
In case you already have the problem of the electrified metal roof and you are not sure what element is causing the problem, seek professional help, and they will have to make a meticulous and timely review of the entire roof, specifically check the points where electrical installations converge on the roof, or on the outside, it will be a task of patience.
Can you screw into a metal roof?
Yes, metal roofs are fastened to the wood with 2″ galvanized screws, These screws have a special rubber washer that seals the screw to the metal surface to avoid small leaks, it is important to use screws approved by the roof manufacturer.
A useful tip is to pre-drill the holes while the metal roof panels are neatly stacked on the ground, this avoids having to mark, hammer, and drive the screws while you are on the roof, the faster you can work on putting on a metal roof, the more comfortable the job will be.
pre-drilling the metal sheet also avoids creating sharp edges around the drilled area with the screw, this prevents breaking the washer on the screw and makes the screw fit much more evenly and neatly into the flat surface of the metal roof.