This study of mesoscopic to macroscopic cataclastic faults in the Loiano Sandstones of the Northern Apennines (Italy) was carried out to quantify the effect of porosity, grain size, grain sorting, clay content, and layering on the structural and morphologic characteristics of fault zones in unconsolidated sandstones. Our observations show that high clay content (<0.05) and/or a poor grain sorting promote a narrow fault zone whereas low clay content and/or a good grain sorting promote a wide fault zone. Slip planes in high porosity (0.12-0.2) and well sorted sandstones develop after an offset of 0.5-1 m has been accommodated by deformation bands; slip planes in sandstones with an high clay content (<0.05), on the other hand, develop after an offset of only 0.1-0.15 m has been accommodated by the deformation bands. The trace of deformation bands in high porosity fine-grained sandstone is anastomosing and braided, different from the more linear traces observed in conglomerates and in clay rich poorly sorted sandstone.