Construction method of around staircase structure and around stairs

摘要

PROBLEM TO BE SOLVED: To provide a spiral stair structure which can make effective use of a space, and which is excellent in strength and also usable as a temporary stair, and a construction method of the spiral stair.SOLUTION: In the spiral stair in which a plurality of spiral step boards are installed in a rotated state at a predetermined angle while height of each step is changed and spiral riser parts are provided each between the spiral step boards, the spiral step board is constituted of a spiral step board base 51 and a spiral step board decorative material 52 fixed on a top face of the spiral step board base 51. The spiral riser part is constituted of: spiral riser plate bases 53, 54 provided at least on the side of an inner end part 51X of the spiral step board base 51 between vertically adjacent spiral step board bases and integrally and firmly fixed to the spiral step board base 51; and a spiral riser plate decorative material 55 fixed to front faces of the spiral riser plate bases 53, 54. The side of an outer end part 51Y of the spiral step board base 51 is attached on a side plate 61, and the side of the inner end part 51X of the spiral step board base 51 is not supported by another member separately provided at a position on an inside of the spiral step board base 51.