Cottage Building in Cob Pise Chalk and Clay Part 8

"I am, etc.,

"JAUCOUR."

_The Virtues of Pise._--"Such is the method of building which has been practised in the Lyonnese for many centuries. Houses so built are strong, healthy, and very cheap, they will last a great length of time, for the French author says he had pulled down some of them which, from the t.i.tle-deeds in the possession of the proprietors, appeared to be 165 years old, though they had been ill kept in repair. The rich traders of Lyons have no other way of building their country-houses. An outside covering of painting in fresco, which is attended with very little expense, conceals from the eye of the spectator the nature of the building, and is a handsome ornament to the house. That method of painting has more freshness and brilliancy than any other, because water does not impair the colours. No size, oil, or expense is required, manual labour is almost all it costs, either to the rich or poor. Any person may make his house look as splendid as he pleases, for a few pence laid out in red or yellow ochre, or in other mineral colours.

"Strangers who have sailed upon the Rhone probably never suspected that those beautiful houses, which they saw rising on the hills around them, were built of nothing but earth, nay, many persons have dwelt for a considerable time in such houses without ever being aware of their singular construction. Farmers in that country generally have them simply white-washed, but others, who have a greater taste for ornament, add pilasters, window-cases, panels, and decorations of various kinds.

"There is every reason for introducing this method of building into all parts of the kingdom; whether we consider the honour of the nation as concerned in the neatness of its villages, the great saving of wood which it will occasion, and the consequent security from fire, or the health of the inhabitants, to which it will greatly contribute, as such houses are never liable to the extremes of heat or cold. It is attended with many other circ.u.mstances that are advantageous to the State as well as to individuals. It saves both time and labour in building, and the houses may be inhabited almost immediately after they are finished; for which latter purpose, the holes made for the joists should not be closed up directly, as the air, if suffered to circulate through them, will dry the walls more speedily."

[Headnote: Indian and Colonial Practice]

-- IV. INDIAN AND COLONIAL PRACTICE

_A Manual on Earthwork_, edited by Colonel Maclagan, R.E., gives much interesting information as to Pise-building and a number of valuable hints:

_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 subst.i.tuted. Even these thin iron bars become so tightly jammed when surrounded by the compact pise 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."

[Footnote 6: India.]

_Soil._--"Soil of a medium quality, that is neither very stiff nor very sandy, is considered best adapted for pise. 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 pise 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."

[Headnote: 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 Pise 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 subst.i.tution 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 3 in. by in.; the upper, 1 in. by ? or in. each, having holes in.

by in., with corresponding pins.

"The mode of setting the bars and arranging the work on each successive elevation of the casing is to cut on the surface of the completed part of the wall a groove 1 in. wider than the bar, filling it in, after placing the bar, with sand, to the level of the wall's surface. The side boarding being set up, the vacant s.p.a.ce left along the bevelled edge of the previous course is filled up with moist clay to retain the first layer of the new course. The end pieces are secured by iron bars or rods, with screws and nuts."[7]

[Footnote 7: "A convenient arrangement might be: to make the lower and upper connecting bars alike, to raise the side boarding a few inches above the upper bars, which, when embedded, might be allowed to remain and become the lower ones of the next course; the external apparatus being shifted by taking out the pins and slipping off the stanchions and planks to be reapplied to the upper bars already in position to receive them."]

_Ramming._--"Gentle and quick ramming has been found most effectual."

_Report on the Pise-work executed at the Etah Jail during 1867-8.

By Mr. H. Sprenger, a.s.sistant Engineer_

"The boxes in which the pise-work at the Etah Jail is being executed consist of two wooden frames 10 ft. long and 2 ft. broad, made of planks, which are nailed on to stout battens. They are held together by four pairs of posts 3 in. by 3 in., which are connected above and below with tie-bars of flat iron 1 in. by in. The tie-bars have at each end a certain number of in. holes punched in them to receive pins for the purpose of preventing the posts from slipping off. By changing the pins, walls of any given dimension can be obtained, wedges of hard wood, with longitudinal slots, are introduced between the posts and the pins, to adjust the breadth of the boxes to a standard gauge. After the boxes are fixed and adjusted, they are secured in their position by ropes pa.s.sing over them, and tied to stakes on each side. Any deflection from the vertical should be corrected at the commencement of the work, as it is impossible to alter the position of a box after it is half full. Any earth which is suitable for brick-making will do for pise-work. On being dug out it is pa.s.sed through a screen with -in. meshes, and thrown into the boxes in even layers of 6 in. in depth.

[Headnote: The Right Quant.i.ty of Water]

"Generally fresh earth contains sufficient moisture to ensure good consolidation; but if it is found that it jumps up under the rammers, it should, on being thrown into the boxes, be sprinkled with a little water out of a tin can with a rose. The watering should be as uniform as possible, as if it is applied unequally it will liquefy the earth, which will commence oozing out under the rammers. Pise-work executed with too much water is worse than if done with dry earth, as, on account of the elasticity of the wet earth, the effect of the ramming is deadened, and the earth remains unconsolidated. The men should be prohibited to keep time in ramming, as it causes vibration, which is injurious to the stability of the wall. On working over a lower course, it is as well to let the lower tie-bars about 4 in. into the same to give the boxes a firm hold on the old work, thereby the joints become imperceptible, and the upper edge of the lower course is prevented from chipping off.

"The implements used are three different kinds of rammers. The earth is first beaten down with a V-shaped rammer, and then surfaced with one with a flat bottom. The sides of the boxes are consolidated with a spade-shaped rammer. When commencing the pise-work at Etah, considerable difficulty was experienced in extricating the lower tie-bars. These were, therefore, supplied with holes 3 in. apart throughout their whole length. A pin was inserted, against which a crow-bar with a long slot and well bent at the end was made to work. An equal pressure could thereby be exerted against the tie-bars; they were thus extracted with great facility without injuring them or the face of the wall, which was not the case formerly."

_Supplementary Note by Mr. E. Battie, Executive Engineer, 5th Division, Grand Trunk Road_

"The work at Etah has generally been concluded in the following manner: In the morning the boxes were taken down, and again put up and filled during the day; they were left during the night, so that the earth might detach itself from the sides. It is not advisable to allow a course to dry thoroughly, as the upper one will not bind well into it, but probably show a crack. If the earth is well rammed, and only the proper quant.i.ty of moisture admitted, a second course can be commenced immediately."

The Report of the Rhodesia Munitions and Resources Committee issued in 1918 contains an interesting paper by Mr. John Hynd on Pise-building, from which the following is extracted:

[Headnote: Pise Buildings at Empandeni]

"_Pise de Terre Buildings_

"_The Spectator_ took this matter up some two years ago and wrote as follows:

"'Various schemes of land settlement are in the air... . All of them must, however, be concerned with cheap buildings. That is a _sine qua non_.' ...

"The material used for the walls at Empandeni is one-third sand, one-third ant-heap, and one-third soil, all pulverised and put through a sieve. Water is then added. The mixture must be neither too wet nor too dry, just sufficiently damp to bind; a good indication of the correct consistency being that when squeezed hard by the hand it shows a tendency to bind. Sufficient of the loose mixture is thrown into the form to fill it to a depth of about 3 in., and this is thoroughly rammed before the next layer is put in. Most thorough ramming is essential.

When the frame is rammed full, it is taken apart and shifted along to make another section and so on until the first layer is complete. The first layer is, as a rule, sufficiently dry to permit the starting of the next about three hours after laying. Door and window frames are put in as the work proceeds, and must be well braced while ramming. In the top layer hoop iron or fencing wire is let in for fastening down the wall plates. a.r.s.enite of soda or Atlas Compound is used in the first layer or two to keep out white ants. The floor can be made of timber, cement concrete, or rammed earth, and the roof thatched or covered with corrugated iron as is most convenient.

"The following Pise de terre buildings have been erected at Empandeni:

"A large schoolroom 75 ft. by 28 ft. by 12 ft. high, walls 14 in. thick; seven boys' dormitories, each 30 ft. by 20 ft. by 12 ft.; twelve single-room houses, each 16 ft. by 12 ft.; six fowl houses, each 20 ft.

by 10 ft.; a large fowl house 250 ft. long, front walls 7 ft. and back walls 5 ft. high. This building is divided into fifteen compartments.

"From the foregoing description it is quite evident that cheap and efficient buildings of this nature can be erected at a very low cost.

"On a farm it is not necessary to employ any skilled labour, as the doors and windows can be purchased ready-made, and the frame-work, clamps, etc., put together by the farmer himself. For a roof of thatch all the necessary material, except iron ridging, if this is used, can as a rule be procured on the farm.

"Should a cement concrete floor, which is cheaper than a wood one, be desired, there would be an extra expenditure for cement, the amount required being about two bags per twelve square yards. Such a floor should be laid before the walls of the building are commenced, and it is essential that the site is thoroughly well rammed and consolidated, particularly below where walls will come, before laying the concrete, to prevent cracks developing through settlement. The concrete raft should be carried at least 6 in. beyond the outside walls of the building, and if the work is properly done, a special ant-course will be unnecessary.

The concrete can be left rough below the walls to give a bond, and it might be advisable to lay some pieces of hoop iron in it which would be left projecting to be bedded into the walls.

"Another good type of floor would probably be that suggested in _The Spectator_, viz. road material laid down and tarred in the same manner as roads are now made in many places.

"A number of rooms and houses have been erected on the Globe and Phnix Mine on much the same principle as Pise de terre buildings, but the system developed there is different as regards the mixture, which consists of two parts ant-heap or ordinary dagga which must not be too sandy, and three parts ashes or clinker sieved free from fine dust.

"A very full description of the method employed on this mine was forwarded by the courtesy of the Manager to the Committee, and it is interesting to note from this that the walls are made waterproof by first making them smooth with dagga plaster, then, when quite dry, giving one good coat of boiling hot tar. A coat of limewash is applied three days later. That this is effective is well evidenced by the fact that the buildings erected have successfully withstood our last abnormally heavy rainy season.