BUILDING. 



true pitch. In these several gradations 

 of changes, the material for the covering 

 has been supposed to be impervious stone 

 or slates ; and the roofs themselves to be 

 those which cover ordinary dwellings; 

 for, after the Italian architecture began 

 to prevail in th last century, platform 

 roofs, and those of a pediment pitch, 

 were introduced in many sumptuous man- 

 sions und public edifices ; but the mate- 

 rial employed for covering was lead. At 

 the present day, when good slates are to 

 be had in abundance, we can execute 

 roofs to the Grecian declivity; but with 

 regard to the general practice, the pitch 

 of ihe roof depends on the style of ar- 

 chitecture introduced in the buildings ; 

 the proportion of the pitch, in ordinary 

 dwellings, is between one-third and one 

 fourth part of the span ; mansions and 

 public buildings are executed in every 

 style that has prevailed in different times 

 and among different people ; and the 

 proportion of the roof, as well as other 

 parts, are rigidly adhered to ; this con- 

 sequently produces a great diversity in 

 the heights. 



There are some advantages in high 

 pitched roofs ; they discharge the rain 

 with greater rapidity ; snow continues to 

 lie a much shorter time on their surface, 

 and they are less liable to be stripped by 

 heavy winds. 



Low roofs require large slates, and the 

 utmost care in the execution ; but they 

 have, however, this advantage, that they 

 are much cheaper, since they require 

 shorter timbers, and consequently much 

 smaller scantling; besides, they huve less 

 pressure on the walls. The roof is one 

 of the principal ties to a building, when 

 executed with judgment, as it binds the 

 exterior walls together. There are a va- 

 riety of forms in the vertical section of 

 roofs, besides the simple and customary 

 one above mentioned. The figure of the 

 roof depends on two or more vertical and 

 horizontal sections. A span, or pent 

 roof, is that which stands upon walls of a 

 quadrangular plan, and of which the 

 transverse vertical section Js every where 

 a triangle throughout its length, and 

 slopes from two opposite sides. A hipt, 

 or Italian roof is that, the sides of which 

 incline alike to the horizon, and termi- 

 nate either in a point, line, or raised plat- 

 form Vitruvius calls a hipt roof, which 

 rises from a rectangular plan, a testudi- 

 nated roof, or simply a testudo. When 

 the plan of a roof is a parallelogram, and 

 when the vertical section across the two 

 opposite walls, which have not a greater 

 span than that across the other two walls, 



consists of four sloping sides on the out- 

 side, each two forming an exterior an- 

 gle, the roof is called a curb or mansard 

 roof, whether there are Cables on the 

 other two sides of the building, or the 

 different sides of the roof, equally in- 

 clined, all around, upon each respective 

 wall 



Figures of roofs which rise from square, 

 rectangular, and polygonal plans, forming 

 only exterior angles on the outside, and, 

 which terminate in a point over the cen- 

 tre of the plan, are denominated from 

 the base on which they rise, and from a 

 vertical section passing through the apex 

 perpendicular to any one of the sides of 

 the base and to the horizon; that is, a roof 

 standing upon a square pentagonal, or oc- 

 tagonal plan, having a triangular vertical 

 section, is called a square pentagonal or 

 octagonal pyramidal roof; when such a 

 roof is said to be polygonal, the epithet 

 only applies to the figure of the base. An 

 octangular roof is one whose base is an 

 octagon, whatever be the form of the 

 vertical section. All roofs, the horizon- 

 tal sections of which are similar figures, 

 either polygons as above described, or 

 circles or ellipses, and the vertical sec- 

 tions of which are segments of convex 

 curves, such as of circles, ellipses, para- 

 bolas, &c. are called domes ; hence a 

 square dome is one that rises from a 

 square plan; an octangular dome, from 

 an octangular plan ; a circular dome from 

 a circular plan ; and an elliptic dome 

 from an elliptical plan. Domes upon cir- 

 cular plans are called cupolas. A circular 

 or elliptical roof, the vertical section of 

 which consists of two similar and equal 

 concave curves meeting in th apex, is 

 called a trumpet mouthed roof. When 

 the roof is circular or elliptical, and the 

 vertical section an isosceles triangle, the 

 apex of which is that of the roof, the roof 

 is simply called a conical orconoidal roof. 

 When the vertical section of a circu- 

 lar dome is a parabola, hyperbola, or el- 

 lipsis, the dome is then called a parabo- 

 loidal dome, a hyperboloidal dome, or 

 ellipsoidal dome, these epithets com- 

 prehending both the base of the figure 

 and vertical section. All figures of roofs, 

 which insist on the foregoing bases, 

 whatever be the form of their verti- 

 cal sections, are called by the general 

 name of pavilion roofs, as they only cover 

 one simple building. Frdm the intersec- 

 tions of two or more simple roofs of the 

 same or of different kinds, a multitude of 

 complex figures will be formed : the 

 plans of some of these are denominated 

 by letters of the alphabet, as an ell roof 



