| 摘要 |
PROBLEM TO BE SOLVED: To provide nice appearance of a boundary part between a riser and a wall surface or a surface on the column side by a method wherein an angle between a riser surface fronting on a riser and a wall surface or a surface fronting on a surface on the column side and a column surface is made approximately equal to an angle between the surface of the riser and the wall surface or the surface on the column side. SOLUTION: A base 21 for a spiral staircase is disposed at a boundary part between the riser of the spiral staircase part having a tread and the riser and a surface on the column side. In this case, an angleαbetween a riser surface 21a fronting on the riser and a wall surface or a wall and column surface 21b fronting on the surface on the column side is specified. Namely, the angleαis made approximately equal to an angle between the surface of the riser and the wall surface or the surface on the column side. Further, a tread surface 21c fronting on the tip surface of the tread is arranged above the riser surface 21a, and an angleγbetween the tread surface 21c and the wall and column surface 21b is specified. Namely, the angleγis made approximately equal to the angle between the tip surface and the wall surface or the surface on the column side. This constitution provides nice finish appearance of a boundary part between the riser of the spiral staircase and the wall surface or the surface on the column side.
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