How can screwing a massively heavy object to a wall with four screws (like a water tank) be safe? I feel its always going to fall, taking a piece of the wall with it.

Question

Or screwing workout equipment which you constantly pull with your own weight.

EDIT: Forgot to add, I’m not in the US, I’m talking about brick or concrete walls, not drywalls. Although probably the basic principle applies when it comes to explaining how force works.

In: Physics

Answer 1

Most of the force applied is pulling DOWN on the wall, not out from the wall, as long as the bolt/anchors are sufficiently deep into the wall. You can easily place a water tank or your body weight on top of a wall without worrying about whether the wall will be crushed, and that’s essentially what’s happening when you mount something properly. You’re creating a vertical force (mostly) at the mounting site. Note that the farther you place the center of mass of whatever object you’re attaching to the wall from the wall itself (like a really long platform), the more you’re going to need to drive the anchors/bolts deeper or add some additional support (like an angled support bracket) to transfer more of the horizontal load to the wall for vertical support.