(i)The internal height of a workroom shall be not less than 4.25 m. measured from the floor level to the lowest Part of the roof and if the roof is of corrugated iron which is neither covered with tiles nor has an inner ceiling or lining of heat-resisting material with an air space of at least 10 cm. between it and the corrugated iron, the internal height shall not be less than 5 m. :
