The joints of the material used must necessarily be considered, and when plain piers or plain wall surfaces occur the joints may readily be accentuated and so turned to decorative account. The edges of the stones forming the separate courses may be chamfered or moulded. The joints may also be worked so as to form a square recess.
The surface of the stone is sometimes roughly tooled or frosted, or worked in an arbitrary pattern, which is termed “vermiculated.” This treatment probably gave rise to the word rustication.
When rusticated work is used with an order the height of each course of stone should not be less than half a diameter, and when square recessed joints are used they can be one-eighth or one-tenth the height of the course.
Occasionally only the horizontal courses are thus marked, and this has been objected to as producing a boarded appearance, though undoubtedly the horizontal effect is at times agreeably in contrast to the vertical features. A much more usual treatment in Renaissance examples was to emphasise the vertical joints also.
The length of each stone should be from one and a half to three times the height.
Rustication may be used in the formation of the arch, which frequently has at its springing line a slightly projecting course, in which the vertical joints are not emphasised.
[Illustration: No. 179. Rusticated Arcade.]
Rustication is also used in columns, either square on plan or conforming to the plan of the column.
Its most legitimate employment is in basements and to emphasise the angles of buildings.
A basement is really a continuous pedestal on which an order rests. It necessarily varies in height according to conditions, thus if its purpose is merely to raise the ground floor it may be no more than three to six feet high, but if it is required to form a storey, it should not exceed the height of the order employed or be less than one half.
The joints of the work in basements are generally accentuated by some form of rustication, and the heights of the horizontal courses should not be less than half a diameter of the column of the order above.
When a high basement is used it is sometimes crowned with a cornice, or more frequently with a slightly projecting facia technically known as a plat-band. In either case, the height should be equal to that of the courses exclusive of moulded edges or chamfers. Also a plinth is placed at the base of the same height as the plat-band or a little more. When a cornice is used the plinth should be moulded and may then exceed the height of the courses.
