You don't need a bunker. Microwaves are very easy to block. All you need is a tight enough mesh of a conductive material like silver or metal.

Blankets like these have been sold for years already to people who are EMF sensitive. Search for "EMF protection fabrics". You can build clothes out of them, make a bed cover, or line your windows and walls with this material. It's the easiest and quickest solution by far.

All the replies are good suggestions but one is missing. Live somewhere with no cell service.

Line the walls under the finish material with 24/26 gauge galvanized steel. Earth ground it. Should also block the peeper vans the cops use to find targets to invent probable cause for raiding.

Other than building a straight-up bunker the only thing that I can think of that would be vaguely practical (using that term lightly) would be to build something like a geodesic dome and cover it with 1 inch wire mesh ( kinda like this chicken coupe )

I think that's narrow enough for 5g, the holes have to be narrower than the peak-to-peak amplitude of the broadcast to block it (you're essentially building an inverted satellite dish)

If you're phone doesn't get reception inside of it, congrats you've done it.

laying the same wire mesh under the floor and using metal doors would seal off your faraday-house.

Also any windows would need a similar mesh (think the window to a microwave)

Almost might as well build the bunker at that point though... the geodesic dome and mesh would make a good frame for spray-crete.

Just a thought.

Don't buy it and tell your friends to do the same. They NEED us to buy it for it to be affordable. Also, if you can find a way, damage the transmitters. They probably aren't bulletproof yet.