PURPOSE: To reduce a construction period of time by covering the front end with an arabesque setting bed without removing the existing roof, and coating the head section of an anchoring device fixing the arabesque setting bed thereto with a starter to roof a new stepped roofing material.

CONSTITUTION: Battens A, roof boards B and a waterproof sheet G are laid on the existing roof α consisting of roof boards α1, an asphalt roofing α2, etc. Then, a cover gutter 2a of an arabesque setting bed C1 is fitted to the front end part of the existing roofing material α3, and a fixed piece 1 of the arabesque setting bed C1 is fixed to the battens A by means of an anchoring device βsuch as a nail, etc. Then, an interlocking piece of a starter C2 is inserted in a fitting groove 3 of the arabesque setting bed C1, at the same time, the fixed piece 10 is fixed to the battens A, an interlocking piece of a spacer D is fitted to a hooking piece of the arabesque C. A lining material E is brought into contact with a bearing piece of the spacer D, and an uneven step decorated surface of a roofing material F is fitted to the interlocking of the spacer D to lay a new roofing material. Accordingly, waterproofing efficiency is promoted to make it possible to prevent corrosion.