BUILDING. 
several giadations of changes, the material 
for the covering has been supposed to be 
impervious stoiie^nr slates, and tlie , roofs 
themselves to be those which cover ordinary 
dwellings ; for, after the Italian architec- 
ture began to prevail in the last century, 
platform roofs, and those of a pediment 
pitch, were introduced in many sumptuous 
mansions and public edifices ; but the ma- 
terial 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 the roof 
deiiends on the style of architecture intro- 
duced in the buildings ; the proportion of 
the pitch in ordinary dwellings, is between 
id and tth 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 pro- 
portion of the roof, as well as other parts, 
are rigidly adhered to ; this consequently 
produces a great diversity in the heights. 
There are some advantages in high 
pitched roofs ; they discharge the rain with 
gi eatcr rapidity ; snow continues to lie a 
much shorter time on their surface, and 
tliey 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, tliey require shorter 
timber?, and consequently much smaller 
scantling ; besides, they have less pressure 
on the walls. The roof is one of the prin- 
cipal ties to a building, when executed with 
judgment, as it binds the exterior waiis to- 
gether. There are a variety of forms in the 
vertical section of roofs, besides the simple 
and customary one above mentioned. Tlie 
figure of the roof depends on two or more 
vertical "and horizontal sections. A span, or 
pent roof, is that wliich stands iqion wails of 
a quadrangular plan, and of which the 
transverse vertical section is every where a 
triangle throughout its length ; and slopes 
from two opposite sides. A hipt, or Italian 
roof, is that the sides of whicii incline alike 
to tile horizon, and terminates either in a 
point, line, or raised platform. ■Vitruvius 
calls a liipt roof, which rises from a rectan- 
gular plan, a testudinated roof, or simply a 
testudo. When the plan of a roof is a pa- 
rallelogram, and when the vertical section 
across the two opposite walls which have 
not a greater span than that across the other 
t>yo walls, consists of four sloping sides on 
the outside ; each two forming an exterior 
angle : the roof is called a curb or mansard 
roof, whether there are gables on the otiier 
two sides of the building, or the different 
sides of the roof, equally inclined, 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 centre 
of tlie plan, are denominated from the base ' 
on which tliey rise, and from a vertical sec- 
tion passing tluough the apex, perpendicu- 
lar to any one of the sides of the base and 
to the horizon ; that is, a roof standing upon 
a square pentagonal or octagonal plan, 
having a triangular vertical section, is called 
a square pentagonal or octagonal pyramidal 
roof ; when such a roof is said to be polygo- 
nal, the epitiiet only applies to the figure of 
the base. An octangular roof is one whose 
base is an octagon, wiiatever be the form of 
the vertical section. All roofs, the horizon- 
till sections of which are similar figures, 
either polygons <is above described, or cir- 
cles or ellipses, and the vertical sections of 
which are segments of convex curves, sucli 
as of circles, ellipses, parabolas, &c. are 
called domes ; hence a square dome is one 
tliat rises from a square plan ; an octangu- 
lar dome, from an octangular plan ; a cir- 
cular dome, from a circular plan ; and an el- 
liptic dome, from an elliptical plan. Domes 
upon circular plans are called cupolas. A 
circular or elliptical roof, the vertical sec- 
tion of which consists of two similar and 
eijual concave curves meeting in the apex, 
is called a trumpet-mouthed roof. When 
the roof is circular or elliptical, and tiie 
vertical section an isosceles triangle, the 
apex of which is that of the rootj the roof 
is simply called a conical or conoidal roof. 
When the vertical section of a circular 
dome is a parabola, hyperbola, or ellipsis, 
the dome is then called a paraboloidal 
dome, a hyperboloidal dome, or ellipsoidal 
dome ; these epithets comprehending both 
the base of the figure and vertical section. 
All figures of roofs, which insist on the 
foregoing bases, whatever be tlie form of 
their vertical sections, are called by the ge- 
neral name of pavilion roots, as they only 
cover one simple building. From the in- 
tersections of two or more simple roofs of 
the same or of different kinds, a multitude 
of coniplex figures will be formed ; the 
plans of some of these are denominated by 
letters of the alphabet, as an ell roof is one 
which rests upon a plan in the form of tlie 
