Organic Matter.—“It has already been observed that no vegetable substances should be left in the earth; therefore in digging, as well as in laying the earth in a heap, great care must be taken to pick out every bit of root, great and small, all sprigs and herbs, all bits of hay and straw, chips or shavings of woods, and in general everything that can rot or suffer a change in the earth.”
ON THE BOND TIMBER TO BE USED IN BUILDINGS OF PISÉ
Corners.—“To make good walls, it is not sufficient that the earth be well beaten, we must also learn to unite them well together. Here the binders cost very little; they consist only of thin pieces of wood, a few cramps and nails, and these are sufficient to give the greatest stability to buildings of pisé.”
Having gone on to explain that the angles of the building are formed by the successive courses alternately crossing one another on the corner like the alternating “long and short” quoins in a stone building, our authority proceeds to describe how rough boards are laid between the courses of pisé so as to cross at the corner and so, entirely encased in tightly compressed earth, they form effective ties.
“This board must be rough, as the sawyers have left it, 5 or 6 ft. long, something less than 1 in. thick, and in breadth about 8, 9 or 10 in., so that there may remain on each side 4 or 5 in. of earth, if the wall is 18 in. thick; by this means the board will be entirely concealed in the body of the wall. When thus placed neither the air nor damp can reach it, and of course there is no danger of its rotting. This has been often proved by experience, as in taking down old houses of pisé such boards have always been found perfectlysound, and many that had not even lost the colour of new wood. It is easy to conceive how much this board, from the pressure of the work raised above it, will help to bind together the two lengths of wall and to strengthen the angle.”
Bonders.—“It is useful (particularly when the earth is not of a very good quality) to put ends of planks into the pisé after it has been rammed about half the height of the mould. These ends of planks should only be 10 or 11 in. long, to leave as before a few inches of earth on each side of the wall, if it is 18 in. thick; they should be laid crosswise (as the plank before mentioned is laid lengthwise) over the whole course, at the distance of about 2 ft. from one another, and will serve to equalise the pressure of the upper parts of the works on the lower course of the pisé.
“The boards above mentioned need only be placed at the angles of the exterior wall, and in those parts where the courses of the partition walls join to those of the exterior wall, the same directions that have here been given for the second course must be observed at each succeeding course, up to the roof. By these means the reader will perceive that an innumerable quantity of holders or bondings will be formed, which sometimes draw to the right, sometimes to the left of the angles, and which powerfully unite the front walls with those of the partitions; the several parts deriving mutual support from one another, and the whole being rendered compact and solid.”
The Strength of Pisé
Strength.—“Hence these houses, made of earth alone, are able to resist the violence of the highest winds, storms and tempests. The height that is intended to be given to each story being known, boards of 3 or 4 ft. in length should be placed beforehand in the pisé, in those places where the beams are to be fixed, and as soon as the mould no longer occupies that place, the beams may be laid on, though the pisé be fresh made; little slips of wood, or boards, may be introduced under them, in order to fix them level. The beams thus fixed for each story, the pisé may be continued as high as the place on which you intend to erect the roof.”