I have spoken with hundreds of geotechnical and structural engineers about proper practices for a foundation investigation. I have asked the question if they would be comfortable rendering an opinion and a recommendation for foundation repair on the spot at a one-time visit. Almost without exception none would be comfortable doing it. Yet contractors all across the country, are "shooting from the hip" daily. Over the years, I have gotten to hear many stories of very interesting on the spot repair analysis. One was to simply put a golf ball on the floor and see where it rolls. Another was to take off your shoes and determine from your feet what the problems are. Folks, these are NOT proper foundation problem investigations. So what should be done in a proper investigation?
If we follow the level B investigation as defined by the FPA or the Texas ASCE then a complete topographical analysis overlaid with a damage map followed by a deflection analysis is required. I’m not saying that that could not be done on the spot. However, I think it would be extremely difficult and time-consuming to do so on-site.
Even seasoned professionals can misdiagnose the cause of cracks in drywall, without proper analysis. I have gone to a home and diagnosed the foundation problem in my mind before analyzing the data carefully. Many times after analyzing the data carefully I have discovered my initial opinion was 100% wrong and backwards. I can easily see how misdiagnosis can happen.
Structural damage in a home's foundation is far too important to the health of the home and its inhabitants to allow conclusions to be drawn without proper foundation inspection / investigation. So, what does a proper inspection look like, anyway? According the the Post Tension Institute, a little something like this.
Rules of Thumb IX: https://www.foundationaz.com/blog/rules-of-thumb-part-ix-signs-of-stress