An attic storey is sometimes used instead of a second order, and this may vary from one-third to one-tenth the height of the order beneath it.
The attic may be quite plain, but it often has breakings or projections on its face corresponding to the vertical features of the supporting order.
It usually forms a storey in a building, and then is of necessity pierced with windows.
In architectural design the character and requirements of the building must, of course, be the first consideration, but the basement may constitute the ground floor, the height occupied by the order may contain two stories and the attic may be an upper floor.
When an order is not employed the divisions and proportions already stated may still be applied, the heights and widths should govern each other as would be the case if the façade were divided into bays by columns or pilasters.
In the absence of the order a cornice is substituted for the entablature, and this, according to different authorities, may be from one-twelfth to one-sixteenth the total height from the ground, but one-fourteenth or one-fifteenth will be found a safe mean.
The pediment in its original and orthodox employment was a gable conforming to the pitch of the roof. It is framed with mouldings, and the enclosed space is technically known as the tympanum.
[Illustration: No. 180. Cornice where order is not employed.]
The use made of the pediment by the architects of the Renaissance was not always justified in the strictest sense. It was often used to vary the sky line, and to form door and window heads. Although the latter use can be to some extent justified in exterior work, a similar employment in interiors may be open to question.
The sloping lines of the pediment are not always straight, sometimes they are in the form of a curve composed of a segment of a circle. The triangular and curved forms are often used alternately in a row of windows with good effect.
The lines of the pediment mouldings are not always continuous; sometimes the sloping or the horizontal lines or both are broken. This is a treatment that cannot readily be justified as the pediment is a feature that implies shelter.
Sometimes ogee curves take the place of the straight sloping lines, and these terminate towards the centre, with scroll ends, leaving an interval between them.