Not a DIY tutorial, but a few examples of what can be hiding behind a “simple” repair: deteriorated masonry, erosion below a slab, water-damaged framing, and severe deck rot. Sharing because some projects are worth pausing on before covering, patching, or cosmetic-fixing the visible issue. Imgur album:

https://imgur.com/gallery/things-seen-this-week-during-structural-assessments-naUBf8W