I'm trying to understand some basic principles here so I can make better design decisions for the deck I'm building.
Suppose I want to fasten a 4x4 post to a joist/piece of blocking/beam/bottom side of stringer. Assume that the screw penetrates both members completely, and penetrates through the face grain of both members. Would it matter whether the screw goes from the post to the other member or vice versa? If so, why?
I have a feeling there may be a difference depending on the shank and the threaded portion of the screw, but not sure how to think about it correctly. My understanding is that the threaded part is what provides withdrawal resistance. But in both cases, the same amount of threaded material is in contact with wood.
If I had to guess at an answer, I'd say that screwing the member into the 4x4 is better: Leverage on the 4x4 will create a withdrawal force that tries to suck the screw out of the other member. If the screw goes through the member into the post, that means that the head of the screw would need to be pulled through the member in order to be sucked out. Whereas if the 4x4 was screwed into the other member, it would be easier to suck the screw out of the other member since it's only the shaft of the screw needs to be pulled out. Is this the right way to think about it?
I've illustrated this question below. Blue is the 4x4, red is the joist/blocking/beam/stringer, and green is the screw. On left, screw goes from joist/beam/etc, to 4x4 and on right, screw goes from 4x4 to joist/beam/etc. (in the case where the red member represents a stringer, the red surface shown is the end grain of the bottom step - i.e. surface to which the first riser would be attached to).
Would the answer to this question depend on whether the red member is a joist or a beam or a piece of blocking or a stringer?