PURPOSE: To reduce cutting work at a site and cutting loss by setting the width of the wall surface and the window frame and also the gap from the end of the wall surface to the window frame in a cabin where the window frames are arranged together with stretched wainscots to a multiple of 150mm, respectively, and setting the height of the window frame to a half of the wall height.

CONSTITUTION: The width of a wainscot 11 stretched over a wall surface in a cabin is set to 900mm and the width L of the wall surface in the cabin is designed to the multiple, based on 150mm that is the divisor of the wainscot 11. In addition, a window frame 12 mounted on the wall surface is designed so that the width 1 can be set to a multiple of 150mm and the gaps X and Y between the end of the wall surface and the window frame when it is mounted can also be set to a multiple of 150mm. The height h of the window frame is designed so as to be a half of the height H of the wall surface. As a result, both the cutting loss of the wainscot 11 and the cutting work at a site are reduced.