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

First, you don’t screw it into the wall, you screw it into the wooden studs within the wall. Screwing into drywall or plaster alone is insufficient for anything but the lightest loads.

Second, if you’re dealing with any sort of significant loads you don’t want to use regular screws you want to use lag screws, which are basically a cross between a big ass bolt and a screw. Normal screws just can’t handle the sheer forces or pullout forces a lag screw can.