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.
It may be noted here, again, that the queen-closers at the angles are at right angles to one another.
In Fig. 100 it has been found necessary to insert four bats to produce a satisfactory bond.
The principles of bonding enumerated in connection with right-angle junctions apply equally well to squint angles, except in the case of obtuse squints, when the closer next to the quoin-header is more often omitted, another expedient being employed to secure the necessary lap of a quarter of a brick in the walls forming the angle. This will be explained in due course.
There are three other rules, the observance of which facilitates good bonding and economises labour.
1. Avoid small pieces of brick.
2. Avoid bird's-mouth cutting.
3. Avoid awkward cutting of any kind.
1. Small pieces will not overlap with the bricks in the courses above and below sufficiently to tie them together.
2. Some writers upon brickwork advocate bird's-mouth bricks for forming the internal angle of squints, on the plea that it gives the angle greater solidity; but as their application is limited to angles of not too pronounced acuteness, and as they are expensive to cut and no particular weakness has been observed in angles bonded without them, their use can only be considered to be a waste of labour.
3. Not only should the builder avoid bird's-mouth bricks, but also all bricks which entail an excessive amount of cutting. In fact, he should contrive to make all bricks of such a shape that they only need one cut with the trowel, or at the most two such cuts.
Fig. 102 shows the method of bonding acute angles. It is best in all cases to make a plan of the extreme corner bricks and determine the exact shape of the quoin brick, which should be accurately cut and the corner rounded as described later. To make this plan, draw two lines AB, BC (Fig. 102) representing the external angle of the walls. Along B A mark off the points D, E, and F, - BD being 4 1/2 inches, De 2 1/4 inches, and Ef 4 1/2 inches. Along BC mark off BG equal to 9 inches. Draw HK parallel to BC, and at a distance of 4 1/2 inches from BC. Draw EK at right angles to BA, cutting HK at K, join KD and draw GL at right angles to BC. This gives the exact shape Bdklg of the quoin brick, and as many of these should be cut as are required to form the angle to the specified height, i.e. two on each face per foot of height. As a preferable alternative, special bricks may be made of the shape Bdklg, one being wanted for each course, as they can be used upside down in alternate courses.
The shape of the closer will be found by the above diagram, but it will be noted that in the case of an angle of great acuteness this closer will be very small, and an arrangement such as is shown in the smaller drawing will give greater solidity to the corner; but in such cases specially made angle bricks are much to be preferred. The walls are then continued as shown, and it may be noted that the wall which shows headers on the external face overlaps, as it were, the wall which shows stretchers on its face, and it also abuts against these stretchers. A certain amount of cutting is necessary, and it should be done in such a manner as to produce large pieces of brick. In the two examples of acute squints shown in Fig. 102 it will be noted that, having drawn one course, the alternate course is obtained by tracing and reversing the first course as with right-angle junctions of walls.
In forming obtuse squints it is possible to do away entirely with closers next to the quoin-headers to secure the necessary lap of a quarter of a brick, and instead single bricks may be cut with one face 2 1/4 inches larger than the other. Squints of any imaginable angle may occur in practice, being produced either by the shape of a site upon which a building is erected or by the fancy of the architect, and it is proposed here, as elsewhere throughout this work, to show a method which will apply directly or with only simple and obvious modifications to every possible case.
As with all angles it is usual to build them up from the quoin brick, the shape of this is first determined in the following manner.
Draw the plan of a brick Abcd (Fig. 103). From C mark off CE equal to 2 1/4 inches the amount of lap. Draw EF, cutting AD produced at F, and making the angle Def equal to the angle of the squint minus a right angle - in this case 120 degrees has been chosen for the squint angle. Hence Def = (120 degrees minus 90 degrees) = 30 degrees. Bisect the angle Dfe by the straight line FG, cutting CD at G, and through G draw Kgh at right angles to FE. From K draw KL at right angles to KG. Then Bcgkl is the shape of the quoin brick for a squint of 120 degrees.