I was thinking about this article and the one portion on screws when evaluating a stairs. Funny thing is I could not find it in the regular Article archives of Nachi.
This is the part I was looking for.
Screws fail in one of four ways:
- Failure occurs through the shank. An example of this occurs when driving screws into a hard material. Screws often snap off just below the head. Deck screws may appear to be securely in place when, in fact, the shank has snapped. Although it looks secure, the head is detached from the shank and the screw has no holding power. You might find this problem by pushing on the materials the screw is designed to join to see if they move separately.
From For Home Inspectors: Evaluating Problems with Fasteners - InterNACHI http://www.nachi.org/home-inspectors-evaluating-problems-with-fasteners.htm#ixzz30DyV0UZw