ELI5: What's the difference between screws and nails in terms of strength and in which situations does one work better than the other?

Nails are quicker (cheaper) to install but can work themselves loose, particularly if subjected to tensile loads. Screws can resist tension without coming loose over time but are more expensive to buy and install.

Whether a nail can work itself loose is mostly the deciding factor in whether to use screws or nails.

As for shear strength: you can't really say nails are stronger than screws because you could always just use a slightly bigger diameter screw to get more strength or install additional screws at a connection, and that's even assuming you need the additional strength - there are relatively few instances where the shear strength between two connected parts is the controlling factor - take the floor boards example - the shear forces there are very small with the strength of the floor dominated by the floor joists, the floor joists will fail long before the screws that connect the floor boards to them. Similarly for most cases where wall panels are connected to wood studs in the wall.

/r/explainlikeimfive Thread