Rule 11.—Divide the number of cubic feet contained in the wall by 306, and the quotient, if any, will show the number of rods, and the remainder, if any, the number of cubic feet.
Rule I11.—Multiply the number of cubic feet in the wall by 8; divide the product by 9, and the quotient will give the area of the wall at the standard : divide the standard area by 272, and this quotient, if any, will show the number of rods ; the remainder, if any, is the reduced feet. The rea son of this rule may be thus shown : 8 9 x 272= 1 9 x 34 = 1 306 which is a divisor of a rod, without any regard to the standard.
length of a wall is sixty-two feet, the height fifteen feet, and the breadth equal to the length of two bricks and a half: how many rods of brickwork are contained in the wall ? 21 In the horizontal dimensions, if the trench is wider at the top than at the bottom, as is generally the case, and equal at the ends, take half the sum of the two dimensions for a mean breadth, and if the breadth of one end of the trench exceed that of the other, so as to have two mean breadths differing from each other, take half the sum of the two Added together, as a mean breadth for the whole.
Or, take a mean dimension in the middle of the length, and the middle of the height, and proceed as in the above operation.
The footing of a wall is the projecting courses of brickwork under the wall, spread out to prevent it from sinking.
To measure the footing of a the length and the height of the course together, then multiply the product by the number of half bricks in the mean breadth : divide the last product by 3, and the quotient is the answer in reduced feet.
The number of half bricks in the mean breadth will be found by adding the number of half bricks in each course together, and dividing the sum by the number of courses ; or take half the sum of the half bricks in the upper and lowermost courses ; but if the number of courses is odd, this trouble may be saved by taking the number of half bricks in the middle course for the mean breadth.
Also, instead of measuring the height of the footing, it is usual to allow three inches to each course in height ; or multiply the number of courses by 3, which gives the height in inches.
Example.—The footing of a wall is 62 feet in length, and consists of 3 courses, the middle course of which consists of 3+ bricks; how many feet of reduced work are in the said footing ? 108 ft. 6 in. of reduced brickwork.
To find the number of rods contained in a piece of brick work. Rule I.—If the wall be at the standard thickness, In the calculation of brickwork, where there are several walls of different thieknesses, it will be quite unnecessary to use the divisors 3 and 272, as will be hereafter shown.
In measuring walls within the districts to which the building act extends, it is customary to take the length of front walls within the building, and the length of party walls from the front to the rear faces of the building, in order to appropriate more easily the share of each proprietor ; but in country houses, which stand insulated, and which have their adjoining faces of the same workmanship, either of the two pair of parallel walls may be taken the whole length of the external faces, and the dimensions of the other pair of parallel walls should be taken perpendicularly from the interior sides of the said walls, or the horizontal stretch of the interior side of either.
In measuring for workmanship only, it is customary to allow the length of each wall on the external side ; or, if all the adjoining walls are of the same workmanship, to girt the whole on the outside ; and consequently, if the building be a rectangle, the contents will by this means exceed the real quantity by four square pillars, each the height of the build ing, and in horizontal dimensions the thickness of each wall. This is a compensation for plumbing the angles ; but this practice is unfair with regard to materials.
In measuring walls that are faced with bricks of a superior quality, the London surveyors measure the whole as if com mon work, and allow so much per rod for the facing, as the quality of the bricks and superior excellence of the work may deserve. The facing may be reckoned at two thirds of a brick.