<p>Foundation elements with load-carrying capacity rely on interface resistance between elements and surrounding soils, which could benefit from utilizing surfaces with structured roughness. The performance and efficiency of foundations’ supporting geo-structures where higher resistance is desired in one direction and lower resistance in the other direction is an advantage. This study focuses on evaluating the influence of structured roughness design on the interface resistance in sandy soils with different characteristics (mainly grain size). A conventional direct shear test apparatus was modified to experimentally evaluate the interface shear resistance of structured (rough-textured) and untextured (smooth) surfaces in two shearing directions. The interface shear tests were performed on locally available fine, mixed, and medium sands at the same shearing rate and over a range of normal confining stresses. The interface shear test results on smooth surface in the three studied sands showed that the difference in mobilized resistance in both directions (interface resistance anisotropy) is marginal. However, results from tests on structured (rough) surfaces suggest that the mobilized shear resistance is direction dependent (i.e., different) when surfaces with different number of elements were sheared against and along the fine, mixed, and medium sand specimens. The results also indicate that mixed sand showed higher anisotropy followed by the medium, while the interface resistance anisotropy was minimal in fine sand. It was also found that the normal confining stress applied at sand-structured (rough) surface interface has a crucial impact on mobilized resistance under monotonic axial loading.</p>