Shutter-ties.—“Cross pieces, as the work proceeds, become so firmly embedded in the wall, that there is great difficulty in extracting them, to remedy which iron bars have been substituted. Even these thin iron bars become so tightly jammed when surrounded by the compact pisé earth, that much labour and risk of injury to the work is incurred in extricating them, and the expedient of setting them in a bed of sand has been successfully resorted to. They are then drawn out with care, the sand also is removed, and the holes which they leave are subsequently filled with the same earth of which the wall is made, and rammed hard.
“The heads of the opposite uprights are held together by ropes, but in practice in this country[6] it has been found that, under the immense pressure exerted upon the plank sides by the earth firmly rammed in the interior, the ropes are so liable to stretch, and to break, that it is advisable to use iron rods or bars in this position also. When ropes are used, the distance between the side planks is measured by gauge rods, and the ropes tightened when requisite to preserve the proper breadth of wall. The use of iron connecting rods renders this unnecessary.”
Soil.—“Soil of a medium quality, that is neither very stiff nor very sandy, is considered best adapted for pisé. It may be said that that which would make good bricks will answer well for this description of work.
“When the earth is very dry, a sprinkling of water will be necessary.”
Foundations.—“It is usual to begin the work upon a foundation of brick or masonry; but there seems to be no reason why the pisé might not be used from the commencement, even for foundations under ground; being carefully guarded from all chance of injury by running water.”
The Building.—“The casing being prepared and erected, and the upper surface of the old work, when above the first stage, being sprinkled with water, the earth, well mixed and slightly moistened, is thrown in, and spread in thin layers of 4 or 5 in. These should, when rammed, be reduced to one-half their original thickness. The rammers should be of hard wood and very smooth. The successive layers are similarly treated, and thus the work proceeds until the top of the casing is reached. The ends of each portion should be finished with a slope, to which will be joined the portion next to be added longitudinally. These joinings should not, in the successive courses, be above those of the lower stage, but as in masonry and brickwork, should ‘break joint.’ The seams are all distinctly perceptible when the work is complete.”
Plastering
Plastering.—“The wall may have a coating of plaster, or the surface may be simply smoothed and dressed with a shovel, or similar implement. When it is to be plastered, it is necessary that the wall should first be thoroughly dry. If dry only externally whilst damp within, it has been found that the moisture is apt subsequently to attack the plaster and cause it to fall off in flakes. Without plaster, good Pisé work is found successfully to withstand exposure to the weather, and after the lapse of many years to be so compact and hard as to be picked down with difficulty.”
Protection.—“Where the wall is not that of a roofed building, it should be provided with a coping, having a good projection to protect it from rain.”
Rods versus Bars.—“The substitution of iron connecting bars for the wooden ones has been mentioned above. The evils of the wooden arrangement were found to be: the starting of the wedges, the fracture of the tenons, the tight jamming of the bars in the wall, and the injury to the walls and to the bars themselves from the force requisite to be applied for extracting them. The lower iron connecting bars are made 3½ in. by ½ in.; the upper, 1 in. by ⅓ or ¼ in. each, having holes ½ in. by ¼ in., with corresponding pins.