Quoins are the external angles or corners of buildings. The name is also applied to the blocks (of stone or bricks) with which those angles are formed. They should, if possible, be built more strongly than the rest of the walling, and are frequently so worked as to be more conspicuous.
Salient external angles of buildings which are greater or less than right angles are termed Squint Quoins. Similar re-entering angles are called Birds' Mouths.
A Coping3 is a course placed upon the top of a wall to prevent wet from entering and soaking into the masonry (see Fig. 128 and others).
The upper surface should be "weathered"4 (see Fig. 131) or sloped (see Fig. 12 9), so as to throw off the rain.
The coping should project a little over the wall on both sides; and should be " throated "4 (see Fig. 131), so that the wet may fall clear of the wall.
1 Sc. Saving Arches. 2 Sc. Scarcements. 8 Sc. Cope. 4 See Note, p. 51.
Brick and stone copings differ considerably in their construction, the details of which will be entered upon in Chap. II.
A Cornice is a large moulded or ornamental course at the top of a wall, and is of the nature of a coping. The name is applied rather to the upper member of a principal wall in a building; whereas a coping generally surmounts a detached or less important wall.
Fig. 15 shows a cornice at C, and more detailed examples will be found in Figs, 118, 147, and others.
A Blocking Course is a course of stone placed on the top of a cornice to add to its appearance, and, by its weight, to steady the cornice, and prevent its tendency to overbalance.
The blocking course in Fig. 1 5 is marked B; and sections of a similar blocking-course will be found in Figs. 329, 476, etc.
The name is also sometimes applied to a thick string course.
A Parapet "Wall is a low wall running along the edge of a roof gutter or high terrace, to prevent people from falling over. See Figs. 322, 469, etc.
A Balustrade is a similar construction, but lightened by being broken into balusters, as shown in Fig. 148, p. 55.
An Eaves Course is a projecting course formed under the lower edges of the slopes of a roof (the eaves), either merely for ornament, or to support a gutter. See Figs. 321, 365.
This, and any other course that projects over the wall, is called a sailing course, and should be throated to keep the wet off the wall below.
The Plinth 1 is a projecting base to a wall, which increases its stability; when not required for this purpose it is nevertheless sometimes added for the sake of appearance.
The kind of plinth varies greatly, according to the style of the building - from a plain offset in the thickness of the wall, to a most elaborate and highly ornamental base.
1 Sc. Intake.
The upper surface of the projection of the plinth should be formed so as to throw off the rain.
In common buildings, with low walls, the plinth is generally-omitted.
The plinth in Fig. I 5 is marked P; see also Fig. 122.
The String Course is a horizontal course (see Fig. 15), often of stone, carried round a building, chiefly for ornament. If, however, the stones are well connected together, it forms a strong band round the walling, and is a source of strength.
The string courses in Fig. 15 are marked S and S1; the latter may, in some cases, form part of the cornice, and is then called a Necking.
In many cases it is necessary to project certain courses of a wall beyond the face, in order to support wall plates, (Figs. 119, 457), for ornament in cornices (Fig. 118), to gain increased base for a chimney or wall above (as in Fig. 473), or in "gathering1 over," or reducing an opening where an arch cannot easily be turned.
This is done by corbelling or projecting each course beyond the one last laid. If the weight to be carried is very great, the portion corbelled out will be proportionately deep, and the projection of each brick or stone should never be greater than 1/3 of its bearing on the course below. The whole of the work corbelled out should not project more than the thickness of the wall from which it is corbelled out.