One way to define the term engineering standard: an established norm or requirement. Engineering standards usually include a formal document that establishes uniform or technical criteria, methods, processes, and practices. The formal document is typically prepared by a professional group or committee and is includes good and proper engineering practices. It normally includes mandatory requirements. It may, and usually does, include unwritten rules.
In fact, the engineering standard used by independent Professional Engineers is usually unwritten. Such an engineering standard is typically changed as an independent engineer gains experience.
The most important elements of an engineering standard for slab foundation performance evaluations
When it comes to creating engineering standards for foundation performance evaluations, there are various sources of material to use:
Building codes: Building codes are of limited use since they address how a foundation should be designed, not how they are expected to perform.
Design protocols: There are design protocols for slab-on-ground foundations on expansive soils, but they too are of limited use. for purposes of performance evaluation. There is one exception to this: the design protocols use a model to design the foundation. The model is a beam on a soil mound. This model is used to estimate the amount of deflection that is likely to result from heaving soil.
Texas Board of Professional Engineers Judgement and Ethics Requirements: In the judgment and ethics sections of the Rules of the Texas Board of Professional Engineers there are many rules that Texas Professional Engineers are legally required to follow. Any engineering standard worthy of the name must be compatible with the judgment and ethics rules.
Many of the rules have clear applicability to foundation performance investigations and reports.
Texas section ASCE evaluation and repair of foundations, version 2: This document was written by a team of 10 members. All of which are Texas Professional Engineers who make residential foundation performance reports. It overflows with good professional advice. I do not agree with every recommendation, but I find gems of wisdom every time I reread it.