Mark makes a good point, but let me expand just a bit.
Customary contract documents (plans/specs and related documents) state that products shall be installed in accordance with BOTH all relevant codes/laws (in the broad sense), AND the recommendations (or requirements) of the product manufacturer (and this includes all industry listing/rating particulars the manufacturer has sought and obtained to ensure its products will, in fact, conform to code/law).
Customary construction contracts and relevant General Conditions also state that all work shall comply with all relevant codes/laws, AND all requirements articulated in the construction documents (plans/specs, and related documents).
Taken together, the controlling law and contract require that the contractor know, understand and comply with all of the relevant requirements. Thus, even if something is not specifically required by code, and even if not specifically shown in plan details, it still is required if it is part of the product listing and/or relevant manufacturer literature (installation instructions, and such).
In addition, for government work, various agencies have their own separate requirements (which are sometimes not readily researched or obtainable, and reside in internal policy papers, guidance to staff, and so on). Those additional policies are sometimes known to designers and contractors, but often they only surface during the course of a project (or, even worse, after the work is done).
So, the answer is not always easily obtained - you have to examine all of the applicable materials in order to come to a final determination.
If a question arises as to requirements, and if the answer is clear (as in an affirmative code section readily quoted), that is great. But, if the answer does not appear in plain-faced code language, you sometimes need to go further before making a determination as to whether something is, or is not required.