Camping house 3x6m or 3x5m + terrace 3x1m

A fully equipped building with roofing, windows and doors;
The “ribs” of the arch are unlined and uninsulated inside.

Arch thickness (for prospective insulation) 125 mm;
Floor frames, insulated, covered with OSB

The camping house 3x6m is shown in the photo

Or a 3x5m + terrace 3x1m house is indicated in the visualization.