_Joint_ 1/8" 1/4" 3/8" 1/2" 5/8" 3/4"
_No. of Brick_ 7-1/2 7 6-1/2 6-1/8 5-3/4 5-1/2
[Sidenote: General Rule]
The method employed in getting these numbers is very simple and
may be applied to any sized brick and joint whatsoever. Thus, take
the brick given in the accompanying illustration (Fig. 58) and let
us use, say, a 3/8" mortar joint. This makes a length of 8-1/4" +
3/8", or 8-5/8" and a height of 2-3/8" + 3/8" or 2-3/4". Hence,
the total area occupied in the wall by this brick, with its mortar
joint, is 8-5/8" × 2-3/4". You can work this out by tractions,
thus, 69/8 × 11/4 = 759/32; or by decimals, thus, 8.625 × 2. 75 =
23.72, the area of the brick and mortar joint in square inches.
[Illustration: Fig. 58. Brick and Mortar Joint]
In either case, to get the number of brick required per square foot
you, of course, divide into 144, the number of square inches in
a square foot. That is, 144 ÷ 759/32 = 144 × 32/759 = 4608/759 =
6-54/759 or about 6-1/15. Or divide 144 by 23.72 and you get 6.07,
which amounts to your previous figure. In estimating the whole
number of brick you need, use no fraction less than the eighth next
above the fraction obtained in your number for the square foot.
Thus in the present example, you will count on using 6-1/8 brick
for every square foot of wall area.
[Sidenote: Quantities for Various Bonds]
As Table 1 gives the quantities for standard size brick laid in
Running Bond, additional allowances must be made for the number of
brick when other bonds using headers are employed. The following
percentages are to be added to the number of brick required, as
calculated by the use of Table 1, when the face brick are laid in
the bonds indicated: