Storage Unit as a Faraday Cage?

[Bartolov]

Could a All steel storage unit with an aluminum roll-up door and a concrete floor be used as a type of Faraday Cage?

I know that due to building codes, all parts in the structure must be bonded to each other as well as to earth ground including the re-bar in the concrete (done because concrete is can be conductive).

 

[Harvey]

I had no idea that connecting was a requirement to connect the rebar in the concrete floor directly to electrical ground was a part of any building codes. If it is, it sounds like it could work, but I'm not sure. The only question I'd have would be whether the rebar was spaced closely enough to be an effective shield from below at the frequencies that concern you.

One easy way to test it would be to go into the unit, close the door, and see if you get any signal with a portable radio station or cell phone.

 

[Mark R]

It may work, but any holes could allow signals in/out. Similarly, the higher the electrical resistance, the less effective the shielding. (so concrete although conductive is not extremely effective as a Faraday cage except at higher frequencies). You are likely to get significant RF attenuation in such a unit, but it really depends on how effective you need the Faraday cage to be, and also what sort of frequency.

As an example, MRI machines need to be installed in a Faraday cage. Typical construction methods for an MRI room include 1/8" copper plate over floor, walls and ceiling with all joints overlapped and soldered. Windows need to include perforated copper sheet (rather like a microwave oven door), and doors need to be copper lined, with nickel plated copper foil/woven fabric covered sponges at the edges, which seal against copper lined door jambs.

 

[Charles Kozierok]

A Faraday cage doesn't have to be solid metal, but any holes have to be smaller than the wavelength of the radiation. Rebar is probably not going to cut it, but it depends on what you are trying to block.

 

[bryanl]

You'll need to add shielding to the roll-up doors or high frequencies will get through, as a test with a cell phone will show.