Preparedness blog

Building Your Own Faraday Cage

By Jeff and Amy Davis
More from this author

A Faraday cage is an enclosed space with an outer layer that conducts electricity. The physical shape of the Faraday cage does not matter: it can be spherical, cylindrical, or a box. Either the cage itself can be made of a conductive material, or the cage can be built of a non-conductive material such as wood and then covered in a conductive material.

The conductive material can be as simple as several layers of aluminum foil, which makes constructing your own Faraday cage a fairly simple and inexpensive affair.

Build Your Own Faraday CageWhat are Faraday Cages Used For?
Faraday cages are designed to guard whatever is inside of it from excessive levels of static and non-static electricity. This can be accomplished either by reflecting incoming electric fields, absorbing incoming fields, or creating opposing electrical fields.

The Faraday cage can help to protect whatever electrical equipment is contained within it from the kind of electromagnetic pulse (EMP), it’s a good practice to keep your emergency electronics such as radios and GPS devices stored in a Faraday cage so they are not incapacitated in the event of an EMP.

How Does a Faraday Cage Work?
Incoming fields are cancelled when the free electrons in the conductive material on the Faraday cage instantaneously realign themselves and block the incident electric field.

For this to work, the cage has to be made from a conductive material; otherwise, the free electrons are not sufficiently mobile to realign themselves. The layer of conductive material can itself be quite thin. This is thanks to the “skin effect,” which is a term that describes the inclination of electrical currents to move mainly on the outer layer of a conductor. Provided that the conductive layer is more than the skin depth of the material, the electrical shielding of the Faraday cage will be outstanding because there will be very high levels of absorption loss.

The skin depth is a function of the material the conductor is made of and the frequency of the incoming wave. Typically, wrapping your Faraday cage in several layers of heavy-duty aluminum foil will give you the needed skin depth to protect your electronics from high-frequency radiated fields like the kind generated by a EMP.

Build a Faraday Cage Building a Faraday Cage
The material you use for your Faraday cage does not have much influence on how effective the cage will be at protecting your electronics from high-frequency fields. Virtually any metal has the necessary conductivity to allow free electrons to realign and cancel out incoming electric fields.

Certain metals, are more conductive than others, which gives them a reduced skin depth – for example, at 200 MHz, silver has a skin depth of less than five microns, as compared to aluminum, which has a skin depth of 24 microns at the same frequency. But on a macro scale, that difference is negligible, which is why you can use heavy-duty aluminum foil, instead of far more expensive materials.

Your Faraday cage can have small holes in it, provided they are not too large with respect to the wavelength of the incoming electromagnetic wave. This is why you can also use fine aluminum mesh to build a larger Faraday cage. For example, a 1 GHz wave has a wavelength of 0.3 meters in space.

Generally with these kinds of mesh cages, the cage door is typically the part that causes the most leakage, but this can be fixed by taping the seams with conductive tape.

You can also use existing metal containers as Faraday cages, including metal ammunition boxes, metal garbage bins, anti-static bags, and even unused microwave ovens. Each of these has its own level of effectiveness: the main concern is that gaps and seams are minimized to reduce leakage.

You do not have to ground your Faraday cage in order to protect the electronics contained within, although doing so will help to keep the cage from becoming charged and possibly re-radiating charge, which could be dangerous if you touch it.

Build a Faraday Cage ShieldLarge Faraday Cages
If you want to build a larger “shield room,” as engineers refer to rooms that are essentially large Faraday cages for storing electronics, you can do so by covering the inside of a small room or closet with several layers of heavy-duty aluminum foil.

Overlap all of the seams and tape them with regular cellophane tape. Cover all outlets, light switches, and other conductive breaches with aluminum foil, and do not plug anything into any outlets. Once the floor is covered in foil, place a piece of plywood over it so you do not damage it by walking on it. Such a room can store all of your emergency electronics and protect them from incoming high-frequency radiated fields.

Have You Made a Faraday Cage?
Have you made a faraday cage or room? Have you ever had to use it? How did it turn out?

Protecting your electronics is extremely important, but so too is a reliable power supply. Don't forget to explore all of our emergency power supplies to ensure that you're never left in the dark.

7 years ago
Comments
Jeanette
7 years ago at 6:53 AM
If you line a room with foil, can you safely ground it through the grounding part of an electrical outlet (leaving the two current parts empty)?
bob johnson
5 years ago at 12:16 PM
grounding is unnecessary and can be counter productive. if that worried add a metal box inside the room for added protection
Brenda
7 years ago at 8:53 AM
Building on Steve's question...would it be advised to enclosed the room containing your battery storage for Solar Power/Wind generators? How would an EMP effect the diodes in your Solar panels?
Brian Talarczyk
7 years ago at 9:10 AM
@Madelaine, No, you can use any metal that is conductive. Aluminum works better than steel as it is more conductive but even better would be copper screen or copper foil. The best conductive metal would be gold, but that's way too expensive (and overkill) for this purpose
Grant
7 years ago at 9:38 AM
@Brian, Point of order: Silver and copper are both better conductors of electricity than gold is.
Jerry
7 years ago at 10:30 AM
Grant is correct; silver conducts better than gold. Gold is a preferred connection matrial because it doesn't oxidize, where silver and copper do, eventually creating poor electrical connections..
mike
7 years ago at 3:42 PM
A small or medium safe or gun safe, with your appliances wrapped in non-conductive material will also fill the bill.
Mike K
7 years ago at 6:11 PM
First, EMP is a real threat to something like our national power grid - lots of very long conductors to capture the EMP and send the resulting current pulse into the computers controlling the power grid. The grid will probably fail. At home, typical power surge protectors will help protect electronics plugged into regular power outlets, not 100% but it will help. Items not plugged in will probably be unaffected, i.e. a laptop not connected to anything (example headphones)will likely not be harmed by a nuclear EMP. I know this is blasphemy but I did EMP testing for many years - small items (talkie-talkie)not connected to cables, especially power outlets, were not harmed. Any small item inside a metal box (old bread box)will not be harmed! Forget the tape. Batteries of any kind will not be harmed sitting outside on a picnic table! EMP can, maybe, damage microelectronic devices if they are connected to wires that direct the EMP to the device. Simple solution - keep your survival electronics unplugged. Don't keep them on a charger. I'm sure other experts will disagree but they are over cautious in terms of preppy needs. The greatest, simple idea I read was a galvanized trash can with a lid (no tape needed)and I consider that overkill!
David L
7 years ago at 8:40 PM
Question - based on what I read, a motor home or even many mobile homes might be inherently Faraday Cages?
NameJerry"G"
7 years ago at 12:40 PM
I have a ham radio (2 Meter ) can I have a antenna hooked to my radio while my radio is in the cage ?
edna
6 years ago at 3:41 PM
Jerry, From everything I've read (and it's been lots) anything with a cord of any type would act as an antenna right to what you were trying to protect. So my opinion would be, no you couldn't.
Mike K
7 years ago at 10:19 AM
Regarding motor home/mobile home - Most mobile homes are made of wood and will not provide much/any protection. Older ones had metal "siding" and might provide shielding. Motor homes these days are mostly made of "fiberglass" or something similar and don't provide much protection. Jerry G - disconnect the antenna. It will "channel" the EMP right into the faraday cage.
Dan
5 years ago at 9:22 AM
Half the mobile homes now have shingle roofs, plus the windows are a point of entry of the EMP. If it had a metal roof you could seal one room off as long as no room close that has a window pointed towards that room as EMP can go through interior walls. I would use a metal garbage can or build a 2x2 cage/box lined with 3-4 layers of heavy duty aluminum foil to keep my my spare tracfone charged yearly in along with 2 walkie talkies and my solar charger for AA batteries and cell phone from Fail Zero. I have a Faraday Bag for my laptop I got off Amazon, 3 pc set for 20 bucks.
Bill
7 years ago at 10:05 PM
I have a GE 3 watt "smart meter" outside my home office wall (that I didn't even know FPL was going to install), and I've been having sleep issues and mental lapses lately. I suspect it's related to the constant RF pulses from the smart meter. How would I go about shielding the smart meter so it doesn't broadcast into my house? Do I need to completely enclose it? Thanks.
NameGeorge
7 years ago at 10:51 AM
Bill: I have issues too with these too "Smart Meters" The RF I was subjected to has affected my sleep and caused me to suffer equilibrium issues until I stopped sleeping in my bed room that as far in line of sight , so to speak, was about 7-8 ft from the meter to where my head was. I corrected that problem with a parabolic dish ( discard Satellite dish network) It worked but appeared to screw with the transmission abilities from the meter to the Electric company...Boo Hoo ...tough crap...Told them their meter was causing health issues and they can either put it on the pole where the power first comes into my property until the wires are underground or put up with the dish or I would sue them as I did have testing done to back me up...they moved the meter!
John
7 years ago at 4:50 PM
Solar Panels can be stored inside a large Faraday Cage, unconnected, and brought out after the attack and hooked up to storage batteries to buffer the energy stored. They would likely be destroyed in any EMP strong enough to damage other electronics equipment if they were outside a cage in use or not. Since a cage can have a lot of very small holes a panel inside could develop electricity, at a much lower power rate, but the wires connecting the panel to equipment outside the cage would likely nullify the effectiveness of the cage. Batteries only supply power a short time till they run out, generators only supply electricity until the fuel runs out, Solar panels while the Sun shines, wind power while the wind blows, water power only as long as you have a flowing stream nearby. Unless you are already set up to supply all the electricity you use, all by yourself, don't expect to be able to rig up some equipment during the emergency to do it, if most of it is subject to the EMP. I suggest you read the book about the Triffids as to conditions you could expect.
Frank
7 years ago at 6:58 PM
Just an observation and my own thoughts: Whatever the situation, I believe that there will be generators, fuels, batteries, radios, etc., that people have stored safely and will be active again. We may not have cable or the internet and 24 hour a day power, but hand cracked (manually) powered devices will be put to use. Some will have solar panels, gasifiers, windmills, etc. So until the batteries die and the motors or electronic devices burn out, we might as well protect those gadgets and not assume we'll all be living in a world without electronics.
Edna
7 years ago at 2:28 PM
I built a couple of faraday cages using the cheap gift popcorn tins that are in abundance around Christmas. I put plastic buckets inside of them and then got some 14g copper wire and grounded them outside my garage attached to a rebar pole I sunk down about 2.5 feet. I put a radio inside them that was on and it went silent so I know it works.
Kathleen
7 years ago at 9:40 PM
Could someone please tell me if I can use staples to when attaching the aluminum foil and/or aluminum screen to my walls? I'm wondering if the magnetic function of steel affects the performance of the faraday cage.
Sonya
7 years ago at 1:34 PM
I am thinking of faraday proofing my shed. Can I use my solar generator to power my fridge in there. If an EMP happens and the fridge is on will that affect it? or am I okay to keep it running?
Allen
4 years ago at 4:33 AM
When I was in the Navy I got a chance to work in an old command radio room. I was a Faraday cage made with copper screen stapled to the walls. To bring power into the room the Navy used saturated core transformer to prevent voltage spikes from entering the room. So it is my guess is that if you do not use something like that then any cord through the wall will act like an antenna and pull RF or E.M.P. radiation into the cage. I was an Electronic Technician although while not a expert on Faraday cages I feel my guess is pretty close. Be careful the cage is usually electrically ground and very easy to short out to.
David
7 years ago at 9:50 AM
Devices like Ham or CB radios will work if the grid goes down( and were`t plugged in or in use at the time). I have 2 portable ham walkie talkies, and 2 CB portables. Both have recharcable batteries, or can use AAs, which I bought in Bulk. Also have a big car cb with upper and lower sideband. All are in Farraday bags and in a lined metal container. With 2 car batteries and 2 stand alone 12 Volt batteries ( for sump pump), communication isn`t a problem if you have energy. Batteries are energy.
Philip
7 years ago at 6:26 AM
A counter top microwave oven (unplugged) is a natural faraday cage especially if your phone or radio is wrapped in foil. Probably can find a couple for free and they stack well if you have more than one.
Roland
6 years ago at 2:27 PM
I use a steel 4 drawer file cabinet. The inside is lined with 1/2" thick Styrofoam panels from shipping crates to prevent contact with metal cabinet & drawers. Cabinet bottom bolted to plywood base with rubber caster wheels. Very inexpensive from used and recycled materials.
LR
4 years ago at 11:38 PM
This sounds brilliant and easy. Does it work? Do you recommend aluminum tape where the drawers open?
premal
6 years ago at 4:27 AM
I want to make a faraday cage/room. already its a brick wall room. how do i make faraday room. 1 side there is window and 1 side is partly brick wall and partly a entry door to the room. other 2 walls are brick wall.
Rho
6 years ago at 2:38 PM
The adhesive on the back of those metal conductive tapes is an insulator and won't help sealing your cage. Maybe if the side edges are folded over on both edges.
Carl
5 years ago at 6:16 PM
I have a question. If I had on grid solar and make way more power than I use it first clicks off grid makes my current usage amount. Then shifts excess solar power to my huge bank of dry cell and gel cell battery's then the excess after that the power goes into the grid. I have 5 10kwh inverters. I was told that in any chance a off EMP or surge they would all kick off like fuses and then a few seconds go by and my whole place kicks over to the back up batts and my solar panels. So would my stuff be protected ?
Wolfe
5 years ago at 2:45 PM
I work in maintenance at a steel mill. Our Electric Arc Furnace has the capacity to produce 175 tons of molten steel every 45 minutes to an hour depending on the grade of steel. You can not imagine the high voltage that is needed to melt steel. Of course, at times the furnace breaks down or is scheduled to have preventative maintenance preformed on it. Certain areas where two metal parts of the furnace meet, we use a insulator spray paint that prohibits electrical current passing between the two metals. I used this same spray paint on the inside of my metal garbage can and the underside of the lid. I then lined the inside of the garbage can. Dont know if this will actually help, but my thinking is yes. I would rather use that extra ounce of prevention than to be regretful later. The paint I used is from the company, Dolph. Product name is Dolph-Spray, ER-41. Specs are as follows: Dielectric strength, 2,000 volts/mil. Also, its made in the good ole U.S.A.
Wings
5 years ago at 12:15 PM
You said tin foil would work....I have put my electronics in a cardboard box and covered it in tin foil...I didn't use heavy duty but I wrapped it 3 times is that enough? Everyone that I have found that says you can use tin foil never tells how many layers you need? Please help I would hate to find my stuff ruined after going through all this trouble....Thanks Wings
bob johnson
5 years ago at 12:30 PM
anything beyond 1 layer is overkill. better to put a layer of cardboard between each layer to create multiple distinct surfaces, each having their own "surface effect" on the pulse
Joe Rhodes
5 years ago at 4:57 AM
Interestingly, any explosion causes EMP, not just nukes. Nukes, causing rather large explosions, cause stronger EMP.
David
5 years ago at 9:49 AM
EMP Isa complicated issue. in all my research on this and my own experiments it seems to be easy to combat but has to be dedicated. Any wire acts as an antenna. Any power distribution system has wires, some very long.. Figure your power Is going off for a looong time! Most info says completely isolate the item in a metal cage either full metal or tiny holes. Putting a radio in a cage and running in an antenna or power cable is like taking a water tank, sealing it completely then running a hose into the side! That means its useless! All literature calls for insulating the item from the cage by lining it with insulation, even say one inch Styrofoam and grounding the cage to the best available ground. Solar panels are connected by cables and although the panels themselves will probably be ok. There are connection blocks on the back with diodes in them which will probably go up in flames!. Then theres your battery controllers and investors! Try a garbage can with tight fitting lid , grounded and lined with foam. Put your radio in on full volume and see what happens. If you can still hear it, its not working! Maybe think in terms of duplcating sensitive items . Good luck.
Tim
5 years ago at 12:23 PM
I've re-constructed a Faraday room when I was working as an electronic technician and we used steel sheeting with braided sleeves acting as gaskets to ensure good contact between the sheets. On the door we used double layer copper screening with copper sheathing wrapped around the edges of the door for protection. Copper door flashing ensured a good seal and everything was grounded to a 8' copper ground rod driven into the ground. We tested it with FM signals (It was for testing custom FM receivers) over the full FM spectrum and it was very quiet.
Mike
5 years ago at 1:41 PM
Forget the GPS gear That system will be toast. Whatever you want to work after needs to be in cage before. Any ideals other than that are going to be a gamble. Remember: no do overs after! To survive you need to be part of a community that has planed for thriving for generations.
Tom
5 years ago at 5:17 AM
A few quick questions. I have some electronics (laptop, etc) still new in the (cardboard) boxes. Would it be enough to simply wrap them in 3 layers of aluminum foil, and, if so, can I stack them with no separating material between them, or do I need to insulate them from each other? Thought I might simply wrap my boxes in aluminum foil, put them in a larger box and stick the whole thing in a closet.
Janean Mcfatten
4 years ago at 6:45 PM
Your state and local taxes would soar and your quality of life would sink while those of us who live in the more affluent states would be just fine.
Rob
4 years ago at 6:27 AM
Question concerning solar panels - The panels themselves will be OK, but the diodes will be ruined. Are the diodes in the panel themselves or in a add-on device behind the panel?
Denny
4 years ago at 9:04 AM
With all the new safes having electronic combinations; how will we be able to to open them in the event of an emp attack?
Lenard Prick
3 years ago at 12:16 AM
Easiest way for a faraday cage for protection from emps is several layers of heavy duty alumimum oil on the bottom and used satelite dish ontop. Wrap all in additional alhminum foil several laysers then duct tape and wrp woth more laers endure all batteries fully charge ams unplugged bury it as well, if you can figure how to run electrictal curremt around it go for it, think of putting a few wristwatchs, satelite phone, and crank radio, and walkie talkie, burner phone pre loaded with different area code in cage
Richard Degnim
3 years ago at 5:05 AM
I have realized that over the course of making a relationship with real estate managers, you'll be able to come to understand that, in every real estate purchase, a payment is paid. Eventually, FSBO sellers never "save" the percentage. Rather, they try to earn the commission by means of doing a great agent's job. In the process, they spend their money along with time to accomplish, as best they will, the jobs of an real estate agent. Those assignments include disclosing the home via marketing, delivering the home to prospective buyers, creating a sense of buyer emergency in order to induce an offer, organizing home inspections, dealing with qualification assessments with the lender, supervising repairs, and facilitating the closing.
Crystle
3 years ago at 3:51 AM
magnificent put up, very informative. I wonder why the other experts of his sector do not understand this. You should continue your writing. I am sure, you've a great readers' base already!
Cap
10 months ago at 10:29 PM
My apartment is between 3 towers that emit EMF waves between midnight and dawn. I want to put copper mesh on the walls and ceiling to protect the room from the waves. If I hang the copper on the walls, can I cover them with fabric or wall paper? Would they still work to limit the amount of EMF waves entering into my room during the night? Or would the fabric covering or wall paper render the copper mesh unaffected? Thank you.
Stanton
5 months ago at 5:33 AM
Your mode of telling all in this paragraph is in fact good, every one can easily understand it, Thanks a lot.