Superhydrophobicity has gained extensive interest in academia and industry. One of the most facile ways of creating superhydrophobic surfaces is the surface-initiated synthesis of 1D polysiloxane nanostructures known as silicone nanofilaments. However, physicochemical details of their synthesis process remain a puzzle, and studies so far have fallen short in explaining the ways in which the 3D film growth transforms into 1D objects. From the observation of hollow cylindrical polysiloxane nanostructures, this study proposes a growth model based on pressure-induced uniaxial elongation of a partially cross-linked polysiloxane film. The pressure build-up is caused by gaseous by-products of hydrolysis and condensation reactions. The presented model aims to promote the understanding of the growth processes, and could thus facilitate the design of robust superhydrophobic coatings onto various surfaces. Furthermore, it is envisioned that novel applications utilizing the tubular nature of the nanostructures could emerge. This article contains supporting information that is available online.