As the sizes of common brick, for all practical purposes,
approximate the size of the standard face brick, their quantity may
be calculated on the same basis. Thus, for a single thickness of
common brick backing, the number required will be practically the
same as that of the face brick laid in Running Bond. If, however,
two or more thicknesses of backing brick are used, the proper
deductions should be made for the thickness of the walls at the
corners.
Two thicknesses of common brick backing will, of course, take just
twice the number for one thickness, and so on. In a word, multiply
the number required for face brick by the number of thicknesses or
tiers of the common brick backing, always considering the turns at
the corners, as just indicated. Where other than Running Bond is
used in the facing brick, allowance should be made for the common
brick displaced by the bonding face brick. The deduction in the
number of common brick, it is evident, just equals the increased
number of face brick required for the bond selected.
In estimating quantities of common brick for fireplaces, figure the
portions projecting beyond the line of the wall, such as breast and
ash pit, as if solid, that is, the number of brick for the surface
multiplied by the number of tiers deep, and then deduct the number
of bricks displaced by all flues and openings, face brick facing,
and fire brick lining.