How thick do underground bunker walls have to be? “Underground bunker”—the words bring to mind military action movies, worst-case weather scenarios and nuclear fallout. With most of those out there in the world somewhere with the potential to happen, there's an undeniable appeal to the idea of a secret, secure place you can retreat to with all the essentials for survival inside. Even the cheapest of pre-made bunkers come to four or five thousand dollars, though, which means that you might want to make your own from scratch instead. But building an underground bunker is a complicated business, and many safety measures need to be taken to ensure that it serves its purpose: keeping you alive.
One of the most basic, but essential, things to know when undertaking this kind of custom construction is how thick an underground bunker's walls have to be. Whether you want to product yourself from earthquakes, bombs and tornadoes, or just want a cool secret hangout spot with statistics that you can brag about to your buddies, one thing is for certain: it's better that the walls are too thick than too thin.
If you want to be sure that your underground bunker can take a beating and stay in one piece, aim to make the walls at least one foot thick. Walls made from one-foot-thick masonry bricks, easily obtained from hardware stores, are sufficient to protect you from tornadoes as well as nuclear fallout. Twelve inches of concrete provide the minimum level of protection from nuclear fallout required for an underground bunker or shelter. If you want to breathe a little easier and not just meet the bare minimum, however, follow the Navy bunker example and use three feet of concrete for the walls of your underground bunker.