When sourcing flat container houses, prioritize the structural integrity of the galvanized steel frame, ensuring a thickness of at least 2.5mm to 3.0mm for load-bearing columns. For insulation, Rockwool or Polyurethane (PU) sandwich panels are recommended over EPS due to superior fire resistance (Class A) and thermal efficiency. Additionally, verify the floor loading capacity, which should typically be ≥ 250kg/m² for standard residential use, and ensure the roof system features an integrated drainage design to prevent water leakage.