How to Build a Faraday Cage for Your Generator

The best way to protect your electronics from an EMP (electromagnetic pulse) is to place them inside a Faraday cage. Many people build Faraday cages using common household items, such as metal garbage cans or ammo cans, because they’re inexpensive and easy to find.

Those methods work well for protecting small devices, but they won’t work for larger items, such as gas generators or high-capacity solar power stations.

In this article, I’ll show you how I built a real Faraday cage that’s big enough to protect that kind of equipment. I’ll walk you through the whole build and give you step-by-step instructions. I’ll also share what I’d do differently if I had to do it over again, along with some practical improvements to make yours even better.

Why Build a Faraday Cage for a Generator?

The main reason you’d want to build a large Faraday cage is to protect your generator or large solar power station from an EMP—specifically the type caused by a high-altitude nuclear detonation. Solar storms can cause widespread electrical damage, too, but the most severe and sudden EMP threat comes from nuclear detonations. An EMP caused by a nuclear detonation will have the following components:

• E1: Super fast, high-frequency, and dangerous for any device, even if it’s not plugged in.
• E2: Similar to lightning. It mostly threatens anything connected to the power grid.
• E3: The “slow burn” part, which also threatens anything connected to the power grid. Small electronics not connected to the grid aren’t at risk from E3.

The main threat to your backup power gear, radios, and LED lighting is from the E1 component. If you’re not protected, it could fry your electronics before you even know what happened.

Materials & Frame Construction

When I set out to build this Faraday cage, I designed it to accommodate some of my larger power equipment, including my EcoFlow Delta 3 Ultra or my Smart Generator 3000. The dimensions I used will also work for common inverter generators, such as the Honda EU 2000i.

Step 1: Build the Frame

• Materials: 2x2s for the top and bottom, 2x3s for the vertical supports, deck screws, pocket screws
• Cut List:
  • Frame: Four 32-inch and four 17-inch lengths from your 2x2s. That makes a top and bottom frame that’s 32 by 20 inches.
  • Verticals: Eight 20-inch pieces from your 2x3s.
• Assembly:
  • Use a pocket hole jig to create two pocket holes at each end of your 8 vertical supports.
  • Sand the boards to remove splinters and rough spots.
  • Use screws and a corner jig to assemble the bottom and top frames.
  • Attach the vertical supports using pocket screws. Using pocket holes and pocket screws is easy and keeps hardware out of the way. It also reduces ridges that could mess up your mesh later. Also, try to keep the verticals flush with the outside edge of your frame. Raised spots can wear down your conductive material over time.
  • Once assembled, use a rasp or sander to knock down any corners or rough edges.

Step 2: Wrapping With Mesh

The next thing you need to do when building a Faraday cage is to add your conductive material to the outside of the frame. This is where I made my first “expensive learning experience.” I went with copper mesh from Amazon.

To be fair, copper is one of the best conductors out there—second only to silver. Unfortunately, it’s a lot more expensive than other materials, such as steel or aluminum. Copper is also difficult to source locally, meaning you’ll have to order it online and wait for it to be delivered.

• Materials: Copper mesh (affiliate link)and copper cut tacks (affiliate link).
• Assembly:
  • Lay the mesh out like you’re wrapping a present. Secure it to the frame with copper cut tacks. They’re easy to hammer, have big heads for gripping the mesh, and, since they’re copper, there’s no risk of corrosion.
  • Wrap each side, and then fold the extra mesh over the edges. Secure the extra mesh to the frame also.
  • Important: Leave one side open. This is where you will put your generator when the Faraday cage is finished.
  • Wrap each end with mesh. Follow the same procedures you did with the other sides.

Money-saving tip: If copper mesh isn’t available or is just too expensive, heavy-duty aluminum foil will work just as well. However, you will need to use more layers.

Step 3: Layering & Sealing

This is where I realized this was going to be a lot more expensive than I thought. With one layer of copper mesh, my Faraday cage blocked radio signals but not cellular or WiFi. I was also trying a new approach for the lid. Rather than creating an actual lid, I attempted to set the cage onto a separate sheet of copper mesh on the floor.

In theory, that could have worked. However, in actual practice, doing that probably won’t form a good metal-to-metal seal around the entire edge. Because of that, I had to add a second layer of mesh and design a new lid. I’ll cover how I made the lid in the next section.

Here is how I completed the mesh exterior:

• Materials: Another roll of copper mesh, 4-inch-wide copper tape with conductive adhesive (affiliate link), and copper cut tacks.
• Assembly:
  • Add a second layer of mesh to each side of the Faraday cage, except the side that will be used as the opening.
  • Secure the mesh to the frame with copper cut tacks.
  • Use copper tape to seal the edges and other areas where the mesh overlaps. Be sure to cover nails with copper tape as well.

Step 4: Lid & Gasket

After the “easy-open” design failed, I built a proper lid out of thick cardboard. I also added a gasket to the top of the Faraday cage and the inside of the lid.

• Materials: Thick cardboard, masking tape, Gorilla tape, 1/2-inch weather seal, 3/4-inch weather seal, copper mesh, double-sided tape
• Conductive Gasket Assembly:
  • Measure each side of the top of your Faraday cage.
  • Cut the 3/4-inch weather seal to those dimensions.
  • Wrap each piece of weather seal in copper tape.
  • Use copper tape to connect the gasket pieces.
  • Secure the gasket to the top of the Faraday cage using copper tape.
• Lid Assembly:
  • Measure the top of your Faraday cage.
  • Cut your large piece of cardboard slightly larger than those dimensions. You want the lid to fit while still leaving room for the weather seal and copper mesh.
  • Cut the side pieces to match the dimensions of your large cardboard piece. They should be 2-3 inches wide.
  • Use masking tape to secure the side pieces to the large cardboard piece. Place the lid on the Faraday cage to check the fit.
  • Use Gorilla tape to finish the lid assembly.
  • Add 1/2-inch weather seal to the bottom inside edge of the lid, along with the interior side edge of the lid.
  • Cover the weather seal with Gorilla tape.
  • Add copper mesh to the bottom of the lid. I used one large piece that I doubled over itself, giving me two layers. It should also cover the sides of the lid. Use double-sided tape to secure the mesh to the bottom of the lid, and use doubled-over copper tape to secure the second layer of mesh to the first.
  • Use copper tape to secure the edges of the mesh to the lid.

Step 5: Internal Platform

Since my original plan of setting the cage over my generator didn’t work, I had to add a platform to the bottom of my Faraday Cage. I used particle board for the main part of the platform, and then placed thick rubber on top.

• Materials: Particle board or plywood, thick rubber stall mat, finish nails, moving blanket
• Assembly:
  • Cut the particle board to the proper dimensions.
  • Cut notches in the edges of the particle board to accommodate the cage’s vertical supports.
  • Use finish nails to secure the particle board platform to the bottom of the Faraday cage.
  • Cut a section out of the rubber stall mat to match the dimensions of the cage’s bottom platform. Note: Cutting the rubber with an oscillating multitool is much safer and easier than using a knife.
  • Place the completed Faraday cage on a soft surface, such as a moving blanket. That will help protect your bottom layer of mesh from damage.

Step 6: Real-World Testing

Proper testing of a Faraday cage requires specialized equipment that is far too expensive for the average person, including myself. However, I do know that it can block a wide range of frequencies from the following tests:

• NOAA Weather and FM Radio: Went to static as soon as the lid closed, meaning all radio signals were blocked or degraded to the point of being unusable.
• Cell Phone: No signal from cellular or Wifi. I wasn’t able to activate the “Find My Phone” feature, and my wife’s phone calls went straight to voicemail.
• Conclusion: Attenuates everything from about 162 MHz (weather radio) to 2.4 GHz (WiFi). That range includes the frequencies most commonly associated with the E1 component of an EMP.

Tip: Nesting gear in Faraday bags or smaller Faraday cages inside the large cage is even better. Layered protection is a good idea for critical equipment.

Is It Worth Protecting a Generator?

When protecting a generator, keep a few things in mind. First, a fuel-based generator will only work for as long as you have fuel. If you’re only able to store a small amount of fuel on your property, it may not be worth going to all of this trouble. However, if you live on a large piece of property and can store more fuel, then it would make more sense.

It’s also worth considering that it may be possible to scavenge fuel for at least a few months after an EMP. After that, gasoline in particular may not be good. Many fuel-based generators can also be modified to run on wood gas if you or someone you know can build a wood gasifier.

Solar generators, on the other hand, don’t rely on manmade fuel sources with finite shelf lives. They can be used for as long as you have sunlight and can power a wide range of small devices and other equipment. Any equipment you plan to use with your power source should also be protected in a Faraday cage.

Recommended: Household Items that Will Still Work After an EMP

Do You Need to Ground a Faraday Cage?

No, you don’t need to ground a Faraday Cage for EMP protection. If a Faraday cage were to be struck by lightning, which is similar to the E2 component of an EMP, then electrical energy could accumulate on the outside of the cage. The only time E2 would be a problem is if your cage were part of equipment that was connected to the grid.

E1 doesn’t work like that, because it’s faster and has higher frequencies. A long ground line running to your faraday cage could act as an antenna and cause more harm than good.

What I’d Do Differently

After going through this process, I would do many things differently to reduce the cost and frustration involved in building this Faraday cage. They are as follows:

• Skip the Copper: It’s too expensive and hard to find locally. Heavy-duty aluminum foil is cheap, local, and can be effective with enough layers. Three layers should provide enough attenuation; however, I prefer to use five.
• Use Cardboard Backers: This will provide a solid surface for the foil to rest on, making it easier to apply. It also helps reduce the chances of the foil getting punctured.
• Maximize Overlap: More overlap means better protection, especially where the lid meets the cage.
• Double Up: Nesting a foil-covered box inside your main cage will provide greater protection. I use this approach with my small electronics. I place them in a Faraday bag and put the bag inside my Faraday trash can.
• Line the Inside with Cardboard: This keeps your gear away from metal mesh or foil and reduces the chance of accidental damage.

Cost Breakdown

In total, this build cost around $290.00 with copper and specialty supplies. A heavy-duty foil build would have cost much less.

• Supplies:
  • Mesh Roll 1: $92.00
  • Mesh Roll 2: $37.00
  • Conductive Tape: $54.00
  • Lumber: $18.00
  • Copper Cut Tacks: $20.00
  • Pocket Hole Screws: $9.00
  • Particle Board: $11.00
  • Window Seal: $12.00
  • Double-Sided Tape: $5.00
  • Rubber Stall Mat: $34.00
  • Grand Total: $290.00

If you’re interested in EMPs, check out these videos!

• 3 Ways to Build a Faraday Cage
• Equipment and Gear to Keep in a Faraday Cage