BRICK EOADS. 9 
does not readily absorb water. Not infrequently one of the shoulders 
is made sufficiently wide to form an earth roadway parallel to the 
brick pavement. Such an arrangement serves to relieve the pave- 
ment of considerable traffic during favorable seasons and also affords 
some advantage to horse-drawn traffic. The general method of con- 
structing shoulders for brick roads is not essentially different from 
that employed for other types of pavements. 
CURBING. 
Brick pavements, as generally constructed, should be supplied with 
strong, durable curbing, both on the sides and at the ends. Otherwise 
the marginal brick will soon become displaced by the Action of 
traffic, and their displacement will, of course, expose the brick next 
adjoining, so that deterioration might eventually spread over the 
entire pavement. Properly constructed curbing, on the other hand, 
will hold the pavement as in a frame and enable the brick to present 
their combined resistance to the destructive influences of traffic. 
Satisfactory curbs may be constructed of stone, Portland cement 
concrete, or vitrified clay shapes made especially for this purpose. 
Wood has also been used for curbs to a limited extent, but when 
it is considered that the life of a brick pavement under ordinary 
conditions should far exceed the life of any wood curb which might 
be devised, the economy of employing a more durable material is 
readily apparent. 
Stone curbing may be made from any hard, tough stone which is 
sufficiently homogeneous and free from seams to admit being quar- 
ried into blocks not less than 4 feet long, 5 inches thick, and 18 
inches deep. On account of their ordinarily homogeneous struc- 
ture, granite and sandstone are probably more used for curbs than 
any other kind of stone. 
All stone curbing should be hauled, distributed, and set before the 
subgrade is completed. The individual blocks should be not less 
than about 4 feet long, except at closures, and should ordinarily have 
a depth of from 16 to 24 inches, depending on soil conditions and on 
whether the curb is to project above the surface, forming one side 
of the gutter. The neat thickness need never be greater than S 
inches and, where the traffic conditions are not severe and the quality 
of the stone is good, a thickness of 6 inches will ordinarily prove 
satisfactory. Stone curb should always be set on a firm bed of 
gravel, slag, or broken stone, not less than 3 inches thick, or on 
unusually firm earth, and should be provided with a backing of the 
same material on the shoulder or sidewalk side. Figure 1 shows a 
typical stone curb in place. 
Where suitable stone is not readily available or when from any 
cause the cost of stone curbing would prove excessive, a curb con- 
40065°— Ball. 373—16 2 
