PURPOSE: To obtain the title structure wherein new roofing material can be constructed without removing a new tile roof established and a construction period can be shortened, by providing an arabesque backing, a supporter, a spacer, a roof material for step roofing, and a lining material.

CONSTITUTION: A fastening strip 1 of an arabesque backing A1 is fastened to the top end part of a new tile roof α established, with fasteners β, and the backing A1 is covered with a supporter A2 in the condition that an engaging strip 12 of the supporter A2 is hooked at the lower end of a vertical strip 3 of the backing. After that, a fastening strip 5 of the supporter A2 is fastened to the roof a with the fasteners β through the fastening strip 1 of the backing A1, and the engaging strip of the spacer B is fitted and secured to a securing strip 10 of the supporter A2, following which the top end part of a lining material C is brought into contact with the supporting face of the spacer B, and an opening almost in triangle shape in section is formed between the lining material C and the roof α. A level difference-facing surface of a roof material D for step roofing and an inserting and engaging strip is fitted to the engaging strip of the spacer B and is laid on the lining material C.