This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol1", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
2. The points H and J are determined as before, and the curve is set out by means of a wood template formed as shown in Fig. 189. This method is essential when the curve of the bow is other than an arc of a circle.
Where great accuracy is required in setting out, the best method of procedure is as follows: Peg out the main points of the building in the manner already shown, a fair degree of accuracy only being necessary. Wooden trestles of the nature shown in Fig. 190 are then erected near all these pegs, as shown in Fig. 187, and sufficiently far from them to be out of the way of the subsequent excavations. The horizontal bars of these trestles should all be at the same level and fixed quite horizontally. The uprights should be braced to prevent any chance of movement.
Lines are then stretched in the approximate positions of the outlines of the walls and foundation, and are carefully adjusted until the whole building is absolutely accurately set out in lines. Nails are then driven into the horizontal members of the trestles in the exact position of the lines representing the walls, while notches are made exactly under the lines representing the foundations.
All the angles, stopped ends, reveals, fireplaces, and all features needing special bonding are commenced first, great care being taken to place the bricks in the lowest course of the footings in such a position that these features may be built up in the exact position shown on the plans without destroying the bond. The arrangement of the bricks in the footings has already been explained. The parts of the plan shown in Fig. 187 which would be commenced first are marked in black.
A rule for commencing the footings under openings properly, with a view to the quoin or reveal-headers falling in their exact positions without destroying the bond, is as follows: -
When the wall is an even number of half-bricks in thickness, commence the lowest course of the footings by laying two bricks as headers so that their axes come exactly beneath the desired position of the jambs of the openings, as shown at AA, Fig. 191.
When the wall is an odd number of half-bricks in thickness, commence the lowest course of the footings by laying two bricks as headers, so that the edges of each come exactly beneath the desired position of the jambs of the opening, as at BB, Fig. 192.
As already explained, when one wall meets another wall at an angle, the course which shows headers on the face of one wall will show stretchers on the face of the other wall. It follows, therefore, that the bricks in the footings beneath the windows W and W1 (Fig. 187) will be different in their arrangement relatively to the position of the jambs. This difference will be accounted for by simply interchanging the terms in italics in the above two cases, - thus if the footings beneath the window W be started as described above, the footings beneath the window W1 will be started according to the above rule with the words "their axes" substituted for "the edges of each," or vice versa as the case may be.
The footings are now completed and the wall built up to damp-proof course level, care being taken that the courses are horizontal throughout. The wall should, if possible, be carried up evenly all over the site to ensure even settlement.
A piece of slate, tin, or zinc is sometimes inserted in the first joint above ground level at the corners, so as to form a projecting ledge upon which to rest the gauging rod, that is, a rod marked off in lengths equal to the depth of the courses, as shown in Fig. 174, care being taken that they are all at the same level.
If any portion of the brickwork is delayed for any reason the corners or portions commenced first are built up, as shown in Fig. 193, each successive course being stopped short of the one below so as to form a stepped appearance. This is called Raking back, and its object is to prevent unsightly cracks from appearing, a defect which frequently occurs when the corners are toothed.
When new walls are being built the corners are built up in successive portions at a time, and the courses raked back as the work proceeds. The faces of the wall are very carefully plumbed with the plumb rule, as shown in Fig. 174. Lines are then stretched between the corners, and the intermediate portions of the wall are built up to the line, the courses being thus kept straight and level. The line is propped up at intervals if the corners are so far apart that it sags appreciably.
When it is desired to extend a building at some future time the walls are usually left toothed, so that the new work may be bonded to the old, and the whole appear as one continuous piece of work, the headers being placed to form the projecting teeth, as shown in Fig. 194. When such provision has not been made a new wall is bonded into toothing formed by "drawing" the bricks of every other course of the old work, and bonding the new work to it as before. When a new wall is built on to an old one at any place other than an angle the old wall is toothed, as shown in Fig. 195, sinkings being made the whole breadth of the new wall, and the height of three or four courses, to a depth of 2 1/4 inches or more, according to the thickness of the old wall. The projecting portions between the sinkings should be at least three courses in width, otherwise the bricks will become loosened when the sinkings are cut. The cutting is performed by means of a crowbar, a cold chisel, mash hammer, or a bricklayer's hammer, all of which are illustrated in Fig. 174.