That might have been my third or fourth. The previous ones were for five or six people (Scouts), with block walls, and saplings and a piece of poly for the roof (covered with loose snow for insulation). We also used snow trenches and tree wells. At some point one of the leaders showed us how to construct an igloo, and it was simple enough I remembered and replicated the task 20 years later during a winter indoc exercise. They ain't difficult.