Building A Faraday Cage


A protective measure to protect electronic devices from the effects of EMP include the Faraday cage.

(Update) The effectiveness of protection depends on several complicated factors including strength of EMP, your geo location from it, EMP altitude, and the gauge and type of metal you are using, and more… Suffice it to say that any makeshift Faraday Cage is better protection than none.

Build a simple Faraday cage from a small metal garbage can and lid.

The lid must fit snugly over the can. If the lid does not make good metal-to-metal contact, the open area could allow EMP to damage your equipment.

To further protect your equipment, purchase a metal screen about 6 inches wide and as long as the circumference of the can. Fold the metal screen in half, length wise, and then place it around (and fold over) the lip of the garbage can. The lid should then fit snugly against the screen and can, protecting all equipment contained inside the can.

Any metal can act as a Faraday cage. Even an ammo can. However, good metal-to-metal contact is imperative.

Remove all gasket material from the lid. If the can has been painted, make sure to remove the painted area around the lid where it contacts with the can itself (and the inside of the lid) with sand paper, so as to make good metal-to-metal contact.


An electromagnetic pulse (EMP) attack on the American homeland is one of only a few ways that the United States could be defeated by its enemies — terrorist or otherwise. And it is probably the easiest. A single Scud missile, carrying a single capable nuclear weapon, detonated at the appropriate altitude, would interact with the Earth’s atmosphere, producing an electromagnetic pulse radiating down to the surface at the speed of light. Depending on the location and size of the blast, the effect would be to knock out already stressed power grids and other electrical systems across much or even all of the continental United States, for months if not years.

Having said that, it may be prudent to protect some electronic items that may be useful post-collapse. Portable AM/Shortwave Radios. 2-way communication radios. Portable solar battery charger. The list can be as long as your imagination…

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  1. Ken Thanks for the info, you answered my question…..I enjoy your articles and I enjoy reading most of the comments.

    1. @George, sure, it’s a metal box designed to keep microwaves OUT, so it should therefore keep the frequencies of an EMP from getting in. If you were wondering… the grid in the front glass is small enough to prevent those frequencies from getting in. However, it is an expensive means of Faraday compared to a metal trash can ;)

  2. is there any reason not to store your electronics gear in a metal can? this seems like a no brainer. thanks for the tip, i’ll add it to my preps.

    1. @mark, Not to store in a metal can? Sure… if you are using it (them), etc.

      A good plan may be to keep extras or spares of certain electronic items in a Faraday ‘Can’, that you may need afterward.

  3. Would my all American canner work? it is big enough to hold a cell phone and small radio. the pressure canner has a metal on metal seal.

    1. @anonymous, yes, a metal-on-metal seal will enable your pressure canner to be a nice little Faraday cage. Big enough to hold a portable radio, etc… Thanks for the idea.

      Beware though that some canners have a rubber seal, which will ‘break’ the Faraday cage properties.

    1. @marta, To some extent, yes the rubber seals on the doors and trunk would break the properties. The only electronic connect points would be the hinges and the latches. I have seen videos where cars have been purposely affected by an experimental EMP, and yes they stopped running. Cars in the approximate era of the 1970’s and earlier are not affected by EMP, due to lack of electronic ignition and computers.

      1. I’ve heard as long as your vehicle isn’t running at the time of the EMP, it shouldn’t be affected, and would run fine after the EMP.
        Your thoughts?

    2. If you can take a portable radio, turn it on and get a signal from inside the car then no a car would NOT be a good faraday cage. Glass and A/C vents would not stop the EMP pulse.

  4. You should be sure to insulate the electronics inside the faraday cage away from the cage itself. A lining of cardboard on the inside of the cage works fine. Second, you should ground the cage to safely bleed off the charges produced by an EMP. Both of these are important to make ensure that your stash is safe from EMP.

    1. @G, those are both debatable points. You will get arguments on either side. Since we haven’t experienced an EMP (yet), and no one really knows for sure, I will agree that extra measures of caution are prudent.

  5. I would agree with G, insulating the interior items from making contact with the cage is essential. Otherwise the cage can work as an antenna to concentrate an EMP and bridge it through the very items you are trying to protect. While we haven’t had large scale EMP’s, we do have other effects that react in the same ways, ESD (ElectroStaticDischarge) and of course lighting strikes. With an EMP, the wavelength matters, this will determine the size of an ‘acceptable gap’, if you look at a MicroWave, the glass door has a mesh built into it, that gap is smaller than the wave of the microwaves, this way you can see in, but it traps the radiant energy.

    The other aspect of it is the grounding. Giving the energy someplace to go. One concern is turning cages into coils that will hold that energy until discharged.

    We do have engineering to go by, and the best way to do a DIY project, is to model it after what is done in commercial products. Faraday cages are available, and you will find that they incorporate those elements. The other thing is in the seal, copper mesh screen is used at any and all openings to assure a good seal.

    This is a good DIY project, but can be GREAT with these few additions. There is nothing worse than a false sense of security. To think you’ve got something covered to only find out when you need it, that it doesn’t work!

    I’m only adding this to hopefully help others, we should work together to try and educate and share knowledge.


    1. @rassd71, as I said earlier, there are arguments on both sides of this issue (to ground or not to ground, and to insulate or not to insulate). Have you ever seen a squirrel running across a high voltage power line without being affected? That is until that squirrel touches a ‘ground’ (the pole or other) while still partially on the line… zap. Jetliners get struck by lightning and people don’t die. It’s all about voltage potential differences, which can get tricky.

      Getting people to at least think about the subject is a first step. It gets you going in the right direction.

  6. Faraday bags can also be purchased for storing electronics. IMHO, using these bags inside a metal garbage can which is insulated inside is the way to go. Just remember if a solar flare produces reverse current flow up from ground to keep your faraday cages away from electrical conduit, wiring and recepticals around the home. In the event of a strong earth directed flare, advance warning will be given and I for one will open all circuit breakers and unplug anything plugged in.

  7. Would a metal building with concrete floor/ rebar be able to have some kind of faraday protection?If not is there a way to make it in to one?

    1. The basic answer in my opinion is, yes, so long as you cover the windows (if there are windows) with screen, and the metal-to-metal is all connected together for good conductivity. Although the concrete floor is sitting on the ground, it is debatable as to the overall effectiveness versus a metal floor or screened floor. My gut tells me that it’s okay, particularly since most concrete has metal rebar within as extra support. If the rebar is tied to a ground rod, that’s even better.

  8. Put you cell phone in the microwave (DON’T TURN THE MICROWAVE ON!) close the door and call your number. If it rings there’s your answer. Faraday cages we made out of copper sheeting in college and grounded to earth couldn’t receive anything inside them. Try the test with a garbage can as well. If AM radio and cell phone signals get through imagine what a huge EMP could do. Chances are if it could kill your radio and car you got a huge dose of gamma rays already.

  9. This is a good idea. I have one for anyone that would also like to save a small older tv, vcr or dvd player. Try your old broken freezer. Metal inside and out with insulation in the middle of the walls. Strip gaskets off of lid ,add latches and seal with aluminum tape. Then bury it deep. Holds a lot and it can be made tight and waterproof..

    1. I have a small none working freezer that I want to place my solar panels in to protect them from an emp…what do I need to do on the inside of the freezer in order to protect my panels… Do you have to bury it? Does solar panels need to be protected from an emp?

    1. Yes, aluminum window screen is conductive, so generally speaking, it will provide similar protection. If in doubt with your particular screen, use an ohm-meter to check for conductivity…

  10. Ken, Would something like a 7000 watt gas powered generator be affected?
    If so, how could that be protected. Any advise is appreciated.

  11. I have a generator 8,000 watt peak that will automatically come on if power goes off. How do I protect that with a faraday cage. It sits on a concrete pad is approx 30 inches wide, 40 inches long and 36 inches high.

    1. Ali, I think Faraday’s original idea was that there was no known insulator to protect something from electro magnetic energy/fields, unlike an electrical insulator that can protect you from direct contact with electrically energized items, like power wiring.
      I suppose if you had something metallic and solid, like a trash can or filing cabinet, sitting on wet/damp ground, it might have a good-enough path to ground, but Faraday’s original concept was to put a grounded metallic, conductive material as a “shield” between the protected device and the EMF, thereby shunting the EMF to ground, & keeping most of it away from your protected device. In recent discussions of EMP, there has been much debate on the need for the ground – but I can tell you, from years of experience, an ungrounded shield on something sensitive does absolutely NOTHING. Of course, just my .02 cents.

  12. When making home made Faraday cages if you don’t have a tight seal you can use steel wool to put a nice layer in the areas it doesn’t fit when putting the lid on. This will help seal it with steel. You can get it fairly cheaply In the paint dept of your local hardware store such as Lowes or home depot. I use 000 fineness ( it is coded like sandpaper) ( Don’t use the soap filled stuff you need the metal on metal contact)

  13. I have a large metal tool box, on wheels. If I were to seal the couple openings like the locks and ground this, would it be a good faraday cage?

  14. i am planning to make faraday cages with steel barrels, but do not understand how to properly ground them. Any advise would be appreciated. Thank you!

  15. My suggestion I used different sizes of military ammo cans, and for and added level of protection some commercial quality alum foil HVAC (heating and a/c vent tape) around the lid and body of the can. The ammo cans also have a nice carry handle. As Far as the LED flashlights they are fantastic flashlight but the bulb is a sensitive electrical component called a LED (light emitting diode) and like transistors, capacitors, resistors they are extremely vulnerable to any type of EMP Almost anything today that runs on a fuel or battery or ac/dc power is going to be prone to a emp event if left outside of a faraday device. Ken thanks for mentioning the microwave in a emergency with some warning we could store a few small items very quickly, maybe even a autos computer module if we had time to remove it and put it in the microwave. The problem coming to my attention, is generators, chainsaws, etc they all would prone to EMP also…..lots to think on.

  16. How does one protect a generator? I have a gas powered generator that I’m sure will get fried in an EMP attack.

    1. @ Bill
      It must be placed inside a Faraday Cage or “Hardened” in a way it’s is in itself a Faraday Cage. As with any electronic equipment.

  17. Where can we get a building plan, specifications and design for building a faraday cage that you can actually sleep in? Do you know anyone who builds faraday cages that you can sleep in?

    1. It is my understanding that an effective faraday cage could be made by shielding the sleeping area in fine mesh wire,… all sides and top and bottom,… like window-screen. I have seen video of faraday cage made from 2×4 frame wrapped in screen. must be metal. not plastic…it worked for isolating a phone… just my thoughts. I have not tried it yet, but it is on the list of things to try…too many things to get done…

  18. I have the same situation as others with a standby generator. It is insulated and heat shielded with aluminum. is it possible to cage only the digital control area from emp?

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