Surface photopatterning of organosilane self-assembled monolayers (SAM) has received increasing attention since its introduction 20 years ago. Herein we report for the first time a cost-efficient soft photopatterning technique affording amplified 3D multilayer structures. The essential chemistry relies on a spatially controlled photoacid-catalyzed hydrolysis and polycondensation of n-alkyltrimethoxysilane precursors (n-C12H25Si(OCH3)(3),). Amphiphilic siloxane species are photogenerated locally and are able to self-assemble spontaneously into a long-range-ordered lamellar mesostructure.