At-Turaif historical district in Diriyah is located northwest of Riyadh, Kingdom of Saudi Arabia. Diriyah was founded in the 15th century and became the center of the administrative power of the House of the Saudi Royal Family, and later the capital of the First Saudi State (1727–1818). At-Turaif administrative district, founded in 1766, was inscribed on the UNESCO World Heritage List in 2010, and has an extension of approximately 235,000 m2, including palaces, houses, defensive structures, mosques, and palatial complexes, representing different wall morphologies, heights, and construction techniques (mainly adobe and stone masonry). In the framework of a thorough condition assessment of the whole site – including vast areas not yet studied nor conserved – Diriyah Foundation Division, within Diriyah Gate Development Authority, commissioned to A.R.S. Progetti S.p.A. a comprehensive set of surveys and studies including a wide on-site experimental campaign for the characterization of the adobe masonry mechanical features according to the different site construction periods and types. A “distributed” approach was adopted for both the employed testing methods and their localization, with the aim of optimizing the achieved results. The campaign included 833 tests on walls, i.e., 813 non-destructive tests (sonic, GPR, moisture content, mortar rebound/penetrometer, OMA tests) for an initial qualification of the areas, subsequently calibrated on the bases of 20 Minor Destructive Tests (MDT consisting of flat jack, endoscope inspections). The paper focuses on the MDT results, which gathered very informative insights, especially with reference to the masonry moisture content, playing a relevant role in the material mechanical response.