To shorten execution work time by making a porch column of support members horizontally fixed to a column at prescribed intervals in the perpendicular direction of a column of a metallic material, a joining member erected in the perpendicular direction on the column and a decorative sheet.

A unitized porch column 2, a porch floor, porch roof eaves and a balcony constituting member are produced in a factory, and these are assembled at a job site. In this case, independent use such as only a floor or only a column and use in a free combination such as a floor and a column and the column and a roof become possible. In a porch unit, after a scaffold is removed after a building main body is completed, these porch columns 2 and 2 and a porch floor 3 or the like are installed, and to cope with damage such as a flaw is taken into consideratiod. Since these are unitized to the porch columns 2 and 2, assembling at a job site becomes easy, and since these have a height adjusting mechanism, a height adjustment of columns and a finishing material can be freely selected.