It has been said above (see p. 17) that the joints across the thickness of walls should be unbroken. This has, however, been objected to on the ground that in bad work - the vertical joints of which are not flushed up, and the face not properly pointed - the rain may be blown through these half-empty straight transverse joints, so as to make the wall damp on the inside. A bond with broken transverse joints is therefore often advocated and adopted, but it has serious defects, which will now be pointed out: -
Figs. 44, 45 show two courses of a 14-inch wall, and Figs. 46, 47, the same of an 18-inch wall with broken transverse joints. Fig. 48 is a plan of the two courses (A and B) of the 18-inch wall, one laid upon the other, A being shown in dotted lines, and B in thin lines. The thick lines, marked y, show portions of the joints which coincide and fall into the same vertical plane.
It will be seen, therefore, that the wall contains splits (marked y) 4 1/2 inches wide, extending from top to bottom of its height, and occurring at intervals of 4 1/2 inches throughout its length.
These are a source of weakness, and may be avoided by adopting the simple plan recommended at p. 17, and shown in Figs. 32, 33 - that is, by making the transverse joints run straight from face to back of the wall.
Figs. 44, 45 Faulty English Bond 14-inch wall.
Figs. 46, 47. Faulty English Bond, 18-inch wall.
Fig. 48. Faulty English Bond, 18-inch wall. Two Courses superposed showing Straight Joints.
When two courses of a wall so bonded are drawn in position, one over the other, as in Fig. 49, it will be seen that the vertical joints coincide only in one place for a length of 9 inches, as shown by the thick line.
The bond of Figs. 44, 45 tested in the same way, will show similar defects to those described, and the same will be found in walls of all thicknesses where it is attempted to break the transverse joints. The student will be able to test any such examples for himself by drawing two courses, one above the other, as above described.
Thus, however good the workmanship may be, the use of broken transverse joints can result only in walls containing defects which must injure their strength, whereas with straight transverse joints the wall is properly bonded in almost every part (see Fig. 49); and if the work is properly flushed up and pointed, as it should be, there is no danger of rain finding its way through the wall.
Flemish Bond shows in elevation (either on one or both faces of the wall, according to the variety of the bond adopted), in every course, headers and stretchers alternately; every header is immediately over the centre of a stretcher in the course below it; closers are inserted in alternate courses next to the corner headers to give the lap.
The appearance of the face which distinguishes Flemish bond is shown in Fig. 50.
Fig. 49. Proper English Bond, 18-inch wall. Two Courses superposed.
Figs. 51 to 54 give plans of two courses and sections taken at two points of a 9-inch wall in Flemish bond.
For thicker walls the back may either be in Flemish bond, like the front, or in English bond: this leads to two or three varieties of Flemish bond, which will now be described.
Double Flemish Bond implies that both the front and back of the wall are built in Flemish bond, presenting an elevation like Fig. 50 on both faces of the wall.
Figs. 55 to 60 give plans of two courses and sections taken at two points of a 14-inch and an 18-inch wall respectively in double Flemish bond. In each case two sections are given - one on A B, through the strongest, and the other on C D, through the weakest part of the wall.
Fig. 57. Double Flemish Bond, 14-inch wall.
Fig. 61. Double Flemish Fond, 18-inch wall.
In these it will be seen that, at certain parts of the wall, straight joints occur throughout its whole depth, as shown by the section on C D in each case. Moreover, in all walls of an odd number of bricks in thickness, a large number of half bricks have to be used in the centre.
The above are objections to this form of bond; and they are greatly aggravated by the usual method of doing the work, shown in Figs. 63 to 70.