Jumping off from Why does the plaster crack beneath the window sill? question, and the calm/collected answers therein.
When (if ever) should I be concerned about the absolute number of cracks around doors and windows, their appearance and growth. I have cracks radiating from the tops of many of my doors and windows, and they have been becoming more noticeable AND numerous over the past couple of years.
Again referencing the above question, when/how would I know if I really do have a structural issue, instead of normal settling? And if I do have such an issue, what kind of expert do I need (what keyword to search for)?
For reference my house is drywall with a complete skim coat of plaster (odd, yeah I know), not merely taped/mudded. The soil when I dig down I would describe as clay-ish, but I am no soil engineer!