18 
BULLETIN 23. U. S. DEPARTMENT OE AGRICULTURE. 
been found to give good results, are contained in the section entitled 
"Typical specifications.''' (Cf. p. 21 et seq.) 
Expansion cushions should be provided for at the time the brick are 
laid, by placing a board of the required thickness on edge adjacent 
to each curb, as shown in figure 3. Small iron wedges, such as are 
shown in this figure, may be inserted between the curb and the board 
at the time the board is set. These wedges may be readily loosened 
and removed after the bricks have been laid and grouted, and may 
consequently be made to facilitate the removal of the board. 
The proper thickness for expansion cushions is a matter concerning 
which much difference of opinion exists among highway engineers. 
Some engineers advocate a minimum thickness of 1 inch, while 
others claim to have secured then best results b} T using expansion 
cushions having a minimum thickness as low as three-eighths inch 
ior very narrow pavements. It is generally agreed, however, that the 
thickness of the cushion should vary with the width of the pavement. 
The following suggestions for proportioning the cushion are offered 
as being fairly representative of the best practice. 
Table 1. — Ratio of thickness of cushions to width of roadway. 
Width of roadway 
(feet). 
Thick- 
ness of 
cushion 
(inches). 
20 or less 
i 
I 
1 
li 
20 to 30 
30 to 40 
Over 40 
Plates III to VII, and Plate VIII, figure 1, show the various steps 
in the construction of a brick pavement. Plate VIII, figure 2, and 
Plate IX, figure 1, show the finished pavement as it should appear, 
and Plate IX, figure 2, shows the advantage possessed by grout-filled 
joints over joints filled with a soft material. 
COST OF BRICK PAVEMENTS. 
The cost of brick pavements varies widely, and is affected by so 
many influences that it is difficult to attempt to derive a general 
expression showing the relation between probable cost and local con- 
ditions. The prices of brick, as also the prices of the various materials 
entering into the foundation, vary greatly according to the locality 
and the freight rate. The cost and efficiency of labor is also far from 
being constant. Furthermore, the material composing the subgrade 
and the method of preparing it may exert a marked influence on the 
cost of the pavement. The following statements regarding cost, 
then, must be considered as representing average conditions, and 
