Earthen architecture holds deep historical, cultural, and ecological value, forming an essential component of our global cultural heritage. However, these structures face numerous threats, including climate change, socio-economic shifts, and, in many cases, neglection, which accelerate their deterioration. This study introduces a photogrammetry-based methodology adapted for the digital documentation and preservation of earthen architecture within the context of developing countries. We focus on the Ex-Hotel Oasis Rouge in Timimoun, an iconic earthen building in southwestern Algeria and the current headquarters of CAPTERRE (Algerian Centre for Earthen Built Cultural Heritage). This paper details our approach to using photogrammetry to capture both the interior and exterior of the building, produce detailed orthophotos for archiving the unique earthen bas-reliefs, and conduct a condition assessment. Our findings demonstrate the effectiveness of photogrammetry as a cost-effective tool for heritage documentation, highlighting its potential to assist in the ongoing preservation and informed restoration of earthen architecture.