(1) Subject to the provisions of subsection (1) of section 24 and to provisions of subsections (3), (4) and (6), the minimum nominal thickness and masses per square metre of glass for vertical glazing in buildings, other than roofs, shall be as set out in Table VIII for each type of glass shown.

(2) The maximum glazing-sizes for the corresponding masses per square metre and nominal thickness of sheet glass and polished plate glass shall be determined by reference to the Second Schedule and Figures 1 and 2 in the Schedule, and these sizes shall not be exceeded except where the opening to be glazed is nowhere more than 3,5 metres above the level interior floor concerned, when the width may be increased by 20 per centum.

(3) Where glass is used in doors, in panes framed on all edges and larger than 0,5 square metre in area, it shall be safety-glass of a thickness to the approval of the local authority for the size of pane concerned.

(4) where glass doors are unframed, they shall be of safety-glass of thickness to the approval of the local authority.

(5) Where transparent glass is used in doors, either framed or unframed or in vertical glazing situated between floor-level and a height of 2 metres above floor level, and, in opinion of the local authority, the presence of the glass may not be apparent to, or suspected by, a person approaching it, the glass shall bear markings which render the glass clearly apparent, except that, where a close approach to the glass is prevented by barrier-wails or other approved means of preventing an accidental collision with the glass, such markings shall not be required.

(6) Any glass louvre, wherever situated, unless supported on both edges shall have a minimum thickness of millimetres and shall have both edges ground smooth.