Cottage Building in Cob Pise Chalk and Clay Part 17

In addition to that, it must be remembered that the cost of material is very small in comparison with that of building. This will be apparent from an a.n.a.lysis of the items employed for actual cost and the percentage which that cost bears to the total cost.

Cottages erected 1912 (semi-detached): total interior area of cottage, 772 ft. super, (parlour, kitchen, scullery and three bedrooms, coal and W.C.):

Per House.

No. Item. Actual Cost. Per cent. of Total Cost.

1. Sundries 8 266 2. Foundations 16 528 3. External and party walls (_a_) 77 2541 Windows and doors (_b_) 23 759 4. Internal part.i.tions 36 1188 5. Ground floor 18 594 6. Upper floor 22 726 7. Roof and rain-water goods 34 122 8. Chimney and fireplaces 30 990 9. Sanitary fittings, water supply and drainage 19 627 10. Staircases 11 363 11. Fittings 6 198 ---- Total 300

These facts help to clarify the problem. The weight of the building materials required for an ordinary cottage with living-room, parlour, scullery, three bedrooms, etc., the house containing cubic contents of about 11,500 ft., would come approximately to 200 tons per cottage; and even a.s.suming that there is only an average transport of fifty miles, this would give 10,000 ton-miles per rural cottage, which is taking it at a very low average. In each cottage the weight of the brickwork represents about 42 per cent. of the total weight. It is, therefore, apparent that every effort should be made to lessen the transit of materials required for the external walling. If, on the other hand, local materials are employed, this carriage would be saved and a great economy effected. Even if this utilitarian consideration were not so important as it is, the desirability of making all possible use of local materials is very great from other points of view. It would stimulate local interest in building and, in addition to retaining the traditions of the district, give greater hope of retaining and maintaining the proper architectural aspect of our villages.

It is scarcely necessary to summarise the advantages that may fairly be expected to flow from this endeavour to make a real start at finding a solution for the housing difficulty. First and foremost must be placed the saving in transport. A casual reader may easily imagine that the difficulties of carriage will vanish with the end of the war, but that is not so in reality. Any one who has travelled in France must have noticed engines bearing such names as Liverpool Street, King's Cross, Euston, Birmingham, and so on. The meaning of that is that a great deal of our rolling stock was sent over to France, and at the best will not be available here for a long time to come. Even the ordinary work of upkeep and repair has necessarily been neglected owing to the scarcity of men and other causes incidental to war-time. Transport difficulties are bound to last for a very considerable period after the peace settlement, and it would not be at all advisable to delay the construction of houses so long. The returned soldiers will make us vividly conscious of the shortage. Nothing could be imagined more likely to make them look for chances of going abroad than to learn that there is not sufficient housing accommodation for them in the village in which they lived before the war, and to which they hoped to return on its conclusion.

[Headnote: Cost per Foot Cube]

III

EXTRACT FROM A LETTER TO THE EDITOR OF _COUNTRY LIFE_, JULY 27th, 1918

"Shortly before the war I had occasion to demolish some very old cottages at Clovelly for the reconstruction of the New Inn. I was so much struck with the stability of these (although by no means first-cla.s.s samples of cob work) that I collected some facts and notes on the subject from different parts of the county of Devon. Where bye-laws have been adopted, cob is no longer being used. It is difficult, therefore, to give an accurate comparison of costs, but after careful investigation I did arrive at the following results for North Devon and Scotland. The prices were in 1913, and in both cases for a five-roomed cottage (a.s.suming four to be built at the same time, including internal water supply, but omitting any special work necessary to procure supply, and omitting fencing).

Cost per foot cube Cost per foot cube cob at 2 ft. 6 in. 11 in. hollow brick.

thick.

North Devon 6d. 5?d.

Scotland 6d. 6d.

These prices a.s.sumed suitable material on or near site, and allowed something for the difficulty of getting at least one experienced cob-worker to instruct the unskilled men. Since 1913 the cost of brick has risen so much that cob would now be much cheaper, probably as much as 1d. or 1d. foot cube in both cases, and this is likely to be the case for many years. Suitable material exists in many parts of the country. If reed straw cannot be had, other reinforcements can be used.

I have seen various materials in use, of which heather was perhaps the best and most easily procured. I can endorse from experience the comfort of these old buildings, and the affection of Devon people for them. The thick walls give all that a house should--protection from heat in summer and cold in winter. For the contrast, visit the new Garden City at Rosyth. Many of the houses are attractive, but their thin brick walls, tile and slate hanging are not suitable to the north and east coasts.

Ask the opinion of the occupants of these new houses. Many of them are Devon born and bred, and imported from the dockyards of the three towns.

They nearly all complain of the cold, and their views form an interesting comment on modern construction."

IV

PISe TESTS

(_With acknowledgements to "The Spectator"_)

Through the courtesy of Messrs. Alban Richards & Co. we are able to publish the results of certain very instructive tests that have been carried out on Pise during the past winter. Messrs. Richard's experience and Report bring out two points with especial clearness, (1) That Pise work, though not impossible under winter conditions, is not ordinarily desirable unless some means of artificially drying the earth be resorted to. (2) That the strength of Pise increases with surprising rapidity as the work dries out. It should be remarked that none of the samples tested were made from really good Pise soil, such for instance as the red marls or brick earths. With such materials or anything approaching them, the results would have been even better, as the Report points out:--

"In conjunction with Mr. Williams-Ellis, we have made certain tests with a view to satisfying ourselves as to the practicability of _pise de terre_ for house construction. In order to obtain what we might term the minimum or 'worst' tests, we decided to erect walls for this purpose in the winter. This we have done for the last three months, which has been a very wet period, and the following is a short description of the tests we have made:--

"1. Two walls were erected measuring 14 ft. long, 9 ft. high and 18 in. thick, s.p.a.ced 20 ft. apart, with short return ends to each wall.

Wall plates were placed centrally along the top of each wall, on which were placed 9 in. by 3 in. wood joists, at 16 in. centres, across the 20 ft span. In order to obtain the minimum results we allowed the shutters to remain until the test was ready to be applied, so that walls did not have an opportunity of drying or hardening. This condition was thought necessary, as it is quite reasonable to expect that if _pise de terre_ cottages are erected, considerable weight might be placed on the walls immediately the shuttering is struck. We then proceeded to test the walls to destruction. The floor s.p.a.ce provided for by the joists referred to above measure 220 super. feet, the load was then applied gradually.

The load applied totalled 16 tons, which is equivalent of 168 lbs.

per super. foot of floor s.p.a.ce, under which the wall collapsed, which, in our opinion, provides a factor of safety of three to the normal load which a cottage floor would have to bear.

"We are convinced that very much better results can be obtained in this method of construction with walls which were first dried before the load was applied. Further experiments are to be made to procure further data on this subject. In addition to the above tests, we have submitted to the National Physical Laboratory, blocks made of _pise de terre_, from poor to medium soil, for testing purposes, and the following are the results which have been obtained:--

"The following Report shows results of Tests made by the National Physical Laboratory.

[Headnote: Pise Tests]

"REPORT ON TESTS OF BUILDING BLOCKS OF PISe DE TERRE SENT FOR TEST BY MESSRS. W. ALBAN RICHARDS & CO., LTD.

"_Tests made on January 14, 1920._

"First set of three blocks sent in November 1919.

"These blocks were composed of a fine gravel containing very few and very small stones. The material was said to be similar to that used at Merrow Down, near Guildford, Surrey. It appeared to be very similar to Farnham gravel.

"The blocks were tested in compression, one within twenty-four hours of arrival at the laboratory, and the others after drying for a time in the laboratory. For results of tests see Table I.

TABLE I

----+------+--------------+----+----+-------+-----+-------+---------- | | | | | | LOAD. | | | |Age |Area|Density+-----+-------+ | | | in | in | lbs. | |in tons| | | Dimensions |days|sq. | per | in | per | No. |Marks.| in inches. | * |ft. |c. ft. |tons |sq. ft.| REMARKS.

----+------+--------------+----+----+-------+-----+-------+---------- UT1 | 3 | 999 | 1 |562| 131 |070 | 166 |Cracked | | | | | |104 | 247 |Collapsed | | | | | | | | UT2 | 1 | 898989 | 9 |550| 125 |427 | 1050 |Collapsed | | | | | | | | UT3 | 2 |895895895|16 |556| 117 |231 | 557 |Small | | | | | |423 | 1020 | cracks | | | | | | | | appeared ----+------+--------------+----+----+-------+-----+-------+----------

[*: Age after arrival at laboratory.]

"Second set of blocks sent in December 1919.

"This set consisted of six blocks in three pairs, each pair having been rammed with a different quant.i.ty of water.

"One of each pair was tested within twenty-four hours of arrival at the laboratory, and the others after drying in the laboratory for twenty-six days.

"The material used was not h.o.m.ogeneous, and the mixture consisted of a very clayey loam, a fibrous loam, sand and large stones. The clayey material gave rise to surface cracks as the blocks dried.

"For results of tests see Table II.

TABLE II

----+------+------------+----+----+-------+-----+-------+---------- | | | | | | LOAD. | | | |Age |Area|Density+-----+-------+ | | | in | in | lbs. | |in tons| | |Dimensions |days|sq. | per | in | per | No. |Marks.| in inches. | * |ft. |c. ft. |tons |sq. ft.| REMARKS.

----+------+------------+----+----+-------+-----+-------+---------- VW1 | 1 | 89985 | 1 |555| 106 |045 |081 |Cracked at | dry | | | | | | | one corner | | | | | |051 |092 |Collapsed | | | | | | | | VW2 | 2 | 999 |26 |562| 105 |215 |384 |Collapsed.

| dry | | | | | | | Material | | | | | | | | quite dry | | | | | | | | in interior | | | | | | | | VW3 | 3 |919189 | 1 |570| 134 |055 |096 |Collapsed | wet | | | | | | | | | | | | | | | VW4 | 4 |888889 |26 |546| 110 |320 |586 |Collapsed.

| wet | | | | | | | Material | | | | | | | | quite dry | | | | | | | | in interior | | | | | | | | VW5 | 5 | 9899 | 1 |558| 126 |060 |108 |Bulged and |medium| | | | | | | cracked | | | | | |069 |124 |Collapsed | | | | | | | | VW6 | 6 | 88887 |26 |546| 109 |333 |610 |Collapsed.

|medium| | | | | | | Material | | | | | | | | slightly | | | | | | | | damp in | | | | | | | | the interior ----+------+------------+----+----+-------+-----+-------+----------

[*: Age after arrival at laboratory.]

Seal of NATIONAL PHYSICAL LABORATORY _Signature of Director_

"From the second set of blocks it would appear that it is better to ram with too much moisture than with too little. It will be noted that the density of the wet block was 30 per cent. more than that of the dry block, so that a wall could be carried higher with the dry material than with the wet, although such a wall would never gain the strength which a wet one would upon drying.

CONCLUSIONS

"We are of opinion, having regard to the fact that the house at Newlands Corner (Guildford four miles) has weathered the winter, without showing any signs of dampness, that _pise de terre_ will make a thoroughly dry house.