MORE ABOUT EARTH HOUSES

New Zealand Listener, Volume 18, Issue 466, 28 May 1948, Page 6

MORE ABOUT EARTH HOUSES

_-s_ AST month "The Listener’ published an article on the use of earth-particularly in the form known as pisé-de-terre-for housebuilding. That article was intended simply to draw attention to a neglected material, but so many readers wanted more informa-

tion that we asked our contributor,

R.

AMMER

to prepare a second

paper, dealing more particularly with the technical problems of pisé construction.’ Copyright in the text and illustrations on this page is reserved to the author.

HE purpose of the previous article was not to instruct tyros in the processes of pisé, but to try to create a vigorous public interest that might develop a public opinion to bring pressure | to bear in high places for the purpose of reducing costs and improving housing, while conserving the valuable and very limited natural resources of the country, including labour. About 30 years ago I set out on a £1,400 experiment involving all the family savings, plus a government loan, and many weeks of toil and sweat to prove to myself, and the public at large, the virtues and possibilities of pisé in modern building. When the building was occupied, the editor of a provincial daily called, and was shown "the works.’ The resultant half-column caused a gmall

avalanche of enquiries. Only one correspondent offered a fee, or a stamped envelope. This one (an architect who could appreciate the value of such information) eventually sent five guineas. Now that I have told how that experiment has confirmed my faith in this "old-new" building material, another avalanche has started. Only two stamped envelopes, and no offers of fees, have arrived in what may be called my "fan mail." However, such are the perils of publicity (somewhat akin to "the uses of adversity’’). The nett cost of the information (which readers are about to get for threepence, of which a small fraction comes to me) was £500. I am still researching with a view to complete mechanisation. Research takes time and money. All I am able to give at present is time. If my work can be completed before I pass on, the result will be given to the nation through the Goyernment on conditions that will prevent monopolistic exploitation and consequent high cost. In the

~- meantime I ask readers to remember that it takes time and money to answer correspondents. Architects Who Sneer One correspondent refers to the sneering attitude of some architects towards pisé. Being in the profession, I can understand it. The one who sneers, perhaps, fears the effect of its general use on his business, if he is more concerned in making money than in providing good homes for the people. Another, through comparative ignorance of the subject, would naturally fear to use it in case it should fail, as happened with an architect a short time before my experiment started. His failure. did not deter me, nor did the remarks of some of my friends, two "cob" builders among them, who could not understand how earth could be made to hold together without being made into mud. They said my walls would not stand two years. If I live to 200 years I will expect to seé them still there but under another roof. o I wrote to the architect, whose earth building venture had been disastrous, to discover, if possible, the cause of failure. No reply came; he probably was too peeved at his failure to discuss it. He need not have met disaster if he had done a little more research before going on with the job. I mention this as a warning to novices to spare no pains in discovering the qualities of the soil they intend to use, and, to protect the material, and the completed courses in the walls, from weather until the whole has been waterproofed. You have heard of the great artist who, when asked by a too voluble admirer, "How do you mix your colours?" replied "With brains, madam!" Well, that goes for building pisé houses. Brains are more important than brawn, but a fair amount of the latter is required, at least till the process is completely mechanised. The successful mechanisation of pisé construction will mean the saving of millions of feet of timber, and thousands of tons of coal, as well as other valuable material. Soil Tests Necessary Now, to the modus operandi. Test the soil before plans are prepared, because until the strength is known the wall thickness cannot be known. Then, unless you know a lot about building, get an architect to prepare plans, or if you design your own have them checked by a competent structural engineer. If the soil is not of uniform quality mix it to get it as uniform as possible. Screen it as fine as possible, within reason, because the finer it is the stronger, and smoother, the finished product will be. * Make blocks at least 15 inches square, then divide into nine equal test blocks with a saw (rip). Keep a record of all yoyr operations; the fineness of soil, weather, weight of rammer, number of

— blows to a given volume of loose soil, the volume of soil used to produce a given size of pisé block, kind and amount of water-proofing, in fact every circumstance connected with the operation. Weigh the blocks when made, at time of test, and again three months later, that is three times. The maximum strength will not be reached in many cases till at least a month after thé blocks are made. Make a reasonable number of blocks, so that fair average may be obtained when testing. Experiment with the moisture content, which must be kept as near the minimum as consistent. with commonsense. Pisé building is not a job for one with a poor sense of values. If you have not learned the art in the course of making the test blocks try again, or employ one who has learned. Have the tests made by a competent person, preferably a P.W.D. officer, or the D.S.IL.R. Keep duplicate check blocks, numbered for reference.

Most soils are suitable, others may be made so by an admixture of clay. Clayey soil may be improved by adding sand. Again use your brains. Do not use a heavy rammer. Many light blows are better than fewer heavy ones. Put no more than two or three inches of loose soil in the form at once, and ram till it gives a kind of ringing sound, which you can only learn by experience. The approximate number of blows of a 4lb. rammer required to make 144 cubic foot of loose soil into one foot of pisé is 1,600, varying according to nature of soil and, vigour of the: workman. Like concrete mixing by hand, the technique of ramming cannot be taught, it must be learned by doing the job. Next ram the forms first with the rammer marked (2) in illustration, then do the rest with the one marked (1). Number (3) is more suited to finishing flat surfaces as at sills and on the top course. The isometric diagram showing forms set on the concrete foundation should be self-explanatory to those capable of building a satisfactory pisé house. This article is not intended for others. Beware of Floods Don’t attempt to build on an area that has even a remote chance of being flooded to floor level. The central tongue, or ridge of concrete, shown on diagram is to resist any (continued on next page)

(continued from previous page) tendency to lateral movement of the wall during an earthquake owing to the lubricating effect of the damp proof course. Remove forms carefully when the course is completed, and waterproof both sides of wall before replacing the form. It is advisable to make the walls an inch or so higher than requitéd so that the surplus may’ be levelled to a sharply defined line by removal, before placing the concrete band to which the roof framing will be fixed. The finish of walls may be textured as desired, but plaster is not necessary if ramming is well done. Any slight inequalities, or accidental injuries to wall, may be made good with any suitable filler, but see that the surfaces and holes are thoroughly waterproofed before filling. Having made your internal wall surfaces perfect in this way (after the roof is on, of course) you may proceed in the usual manner to paper, paint, or distemper, as desired; and blame yourself if you're n@t satisfied. Pise Holds Nails Follow the usual building practice as for brick and concrete houses with regard to carpentry and joinery, etc. Except in special cases, no grounds or methods for fixing are needed, because pisé holds nails well if they are 2in. or more into the wall. Where concrete is not used at door and window openings, use foxwedged cylindrical plugs bedded in plaster of paris in holes bored with brace and bit. Waterproof hole and plug before plaster is used, make the plug lin. diameter and at least 6in. long. External angles, and all openings, unless of concrete, should be rounded to a 2in. radius. Referring again to the diagram, the spacer (c) to maintain a constant thickness of wall, is removed when the form is about three-quarters full, and is best placed below, or near, the %in. dia. tiebolts. The minimum value of A and AT is 12in. for external, and 6in. for internal walls of highest quality pisé. Minimum value of B must be calculated according to the known bearing power of the ground below the footing, in relation to the load that will be imposed upon it. The forms should be of 2in. timber, lined with sheet steel for smooth finish, and should lap the previous course at least four inches. Should sufficient inducement offer, or in other words, if there is a reasonable prospect of doing so without financial loss, I intend to publish a fully illustrated text book on earth buildings. This book will deal with: the subject much more fully than can be done in a short magazine article, and will contain among other features a few modern designs suitable for construction in pisé. Now, readers, it’s your move. Give a day and save a tree! (To my many correspondents I apologise for the delay in replying to their enquiries. All letters will receive attention now that the above article is off my hands. Naturally, those who enclosed stamped envelopes will be dealt with first. Should the public reaction warrant such a course, I will, in spite of the fact that I have retired from business and professional activity, provide myself with suitEble portable equipment to enable me to visit proposed building sites and make tests for the purpose of preparing reports with regard to the suitability of such sites, and their soil, for pisé construction.-R.A.).