Nails and screws are the two most common fasteners involved with construction. Many people ask which is better. Generally screws would be better, but this depends on a number of additional factors.
Nails are excellent shear fasteners meaning they resist being broken in two. On the other hand human force can pull nails out with minimal tool assistance. Screws are good shear fasteners, but are excellent at resisting pullout forces.
Other than the fastener itself the material fastened dictates the strength of the connection. Direction of grain, thickness of material, penetration depth all are significant factors. As a general rule to develop the full strength of the connection the fastener must be at least 1/3 the depth of the fastener into the second material or fully penetrated both materials.
It is important to use the correct type of fastener with the appropriate material. Drywall screws are brittle and have wide thread fins to reflect the material used. Wood screws are heavy duty compared to most other screws of the same size, but have threads too narrow for drywall and spaced too far apart for metal applications. Nails are similar, drywall nails are short and broad headed to be puttied over while masonry nails are cement coated to bind better with the material.
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