Cottage Building in Cob Pise Chalk and Clay Part 15

From this cause the "waste" is sometimes considerable.

The well-known building "stones" from the quarries of Beer, Sutton, and Tottenhoe in Devons.h.i.+re are really chalk, but in a form not readily distinguishable from ordinary free-stone.

The longer that chalk blocks are kept to dry before building-in the better, and the sun and wind of at least a year should be allowed free play upon them to dry out their natural sap and render them "frost-proof."

During the drying-out process the chalk should, if possible, be protected from the rain.

For years after being built into the walls of a house, chalk will continue to dry and harden.

But it is essentially a somewhat porous material, and will quickly revenge itself on those neglecting its just demands for a sound roof and a proper damp-course.

In exposed situations new chalk walling is liable to allow the penetration of moisture under the pressure of the wind unless a cavity is provided or unless the surface is treated with a silicate or other "vitrifying" fluid.

Chalk, however, has one s.h.i.+ning virtue in common with its great ant.i.thesis--it improves mightily with keeping.

Chalk walls sometimes have youthful vices in the way of porosity that entirely disappear with advancing years through the closing up of the surface pores, which eventually makes a cavity and inner lining superfluous.

IV

_UNBURNED CLAY AND EARTH BRICKS_

SUN-DRIED BRICKS

The use of sun-dried bricks in this country, is, for no very apparent reason, almost entirely restricted to East Anglia. There it has been used for generations with entirely satisfactory results.

Mr. Skipper of Norwich writes of the material as follows:

"Who, travelling from Norfolk to London, whether by the Ipswich or Cambridge line, has not noticed the numerous colour-washed or black (tarred) cottage, farmhouse and agricultural buildings scattered practically all along the countryside? Some of these are of studwork and plaster, some of wattle and daub, but many are built of clay made up into lumps, sun-dried, and built into the walls with a soft clay-mixture as mortar. No lime _need_ be used, though sometimes it is mixed with the clay mortar. The preparation, digging, exposure and mixing with short straw are similar to the Devons.h.i.+re 'cob' work, but in these parts the worked clay is thrown into moulds, and lumps are formed of, say, 18 in.

by 12 in. by 6 in., or 18 in. by 9 in. by 6 in. for large sizes, and for inside walling or backing to brick-faced walls, 18 in. by 6 in. by 6 in.

The walls, naturally, are rough in texture and the joints are generally stopped up and besmeared with a thin coating or almost a wash of clay.

This coating sometimes has lime mixed with it, but it is not necessary.

This is all that is needed to complete the walling, and there is a building--a malting, that any one can see at Tivetshall Station on the Ipswich line, about 200 ft. long, 45 ft. or 50 ft. wide and three floors high, built of lumps 18 in. by 12 in. by 6 in.--that has stood the weather and weight of its roof for forty years built in this way; 12 in.

is the thickness of its walls. A further stage in finish is to give the walls two or three coats of coal tar, but it is not essential, though desirable where stock are kept, as cattle are rather fond of licking the clay, and they do not use their horns much when walls are tarred. The highest finish in this work is to cast sand on the last coating of tar before it is quite dry, and then to colour or whitewash on this. This accounts for the variety of colourings seen in these buildings, some even of a kind of pink or red; while some yellow or buff, beside the white and the black or tarred buildings, and all huddled together or standing apart, whether covered with thatch or red pan or flat tiles, look remarkably in harmony with their surroundings. These lump walls are, of course, built on a base of brickwork, about 18 in. or 2 ft.

high, to keep them free from damp. This kind of walling can be built for _at least_ 15 per cent. or 20 per cent. cheaper than ordinary 9 in.

brickwork. Thin as these walls are compared with those of 'cob' houses, they are noted for being warm in winter and cool in summer. When suitable clay is procurable a local builder almost invariably uses clay lumps when building a house for himself, though to gratify a whim perhaps, he will case the outside walls--especially the front next the street or road--with brickwork. But clay lumps he carefully reserves for inside walls and weight-carrying linings to the outside walls, bonding the two together very much in the same way as two 4 in. 'cavity walls'

are bonded. I am not suggesting that this walling is as interesting artistically as 'cob,' but I do suggest it is a practical, sensible and _dry_ walling, and if properly done it will 'last for ever,' as a local builder repeatedly said to me when speaking of it. One can easily see why the cost is light--the sun and the winds do the drying in the spring months, and no coals are required, and also the clay is often found on the building site, hence no cartage. Actual building work naturally goes quickly, as the lumps are large. There is another important point to notice. One may see a building complete with its roof on and occupied by its tenant while still awaiting an outside casing of brickwork to be built round it, either with a view to greater protection or for the mere vanity of the owner, for while thus left unprotected the lump walls take no harm from even winter exposure. Now to be quite practical in these extremely practical days, I venture to suggest that the use of clay lumps at least for inside walls and linings of outside walls would be an immense boon to the numerous cottage-building schemes now being projected. We must not forget that comparatively few bricks will be available this year, while the cottages are wanted at once. Can these few bricks be better used than by forming foundations and chimneys for the clay-lump walls of these cottages? I think not. The cottages could, of course, be occupied in the late summer or autumn of this year, and next year when bricks will be more plentiful perhaps the brick casings could be added, if brickwork _must_ complete them. I make this strictly utilitarian suggestion solely to meet a very urgent and deep national need. Personally, I prefer the sight of a cottage built and finished in the old-established method of the locality. Unskilled labour only is required, working under intelligent supervision, hence immediate employment for a great number of men would be provided."

[Headnote: Use for Unskilled Labour]

[Ill.u.s.tration: +Once Corn Hall, now Council School.+ Built about a hundred years ago. Still in sound condition and quite dry.]

[Ill.u.s.tration: +A Row of Clay-lump Cottages.+ The front has been plastered and panelled out. In the upper part of the stable building, seen in the foreground, the clay-lumps are shown exposed.]

[Ill.u.s.tration: +Engineering Workshops.+ Built twenty years ago. The walls are thoroughly sound, despite constant vibration, and are perfectly dry, except the brick face, which was added for effect.]

The use of sun-dried bricks for the interior part.i.tions of cob and pise cottages is worth consideration, as the nature of these materials demands a thickness of wall which is too wasteful of s.p.a.ce to be acceptable in mere part.i.tioning.

Of the strength of clay-lump walls, there is no question. It was recently necessary to cut a new doorway in the old clay-lump wall of a large traction-engine garage, and the blocks removed were thrown into a heap upon the ground.

The clay happened to be needed for other purposes, for which it had first to be broken up.

Ordinary hammers proved entirely ineffective, and it was not until heavy sledges were used that the lumps could be smashed.

The tractor-house in question is a large building some 25 ft. by 100 ft., carrying a heavy roof and constantly subjected to vibration by the coming and going of the tractors.

The walls are only 12 in. thick, without piers or reinforcements of any kind, and yet the whole building, which is 26 ft, high at the gables, is as perfect to-day as when first erected some twenty years ago.

In the same town as this tractor-house, East Harling in Norfolk, is a council school built of clay lump (converted from the old Corn Hall), apparently not a pin the worse for a century of hard wear.

Near by there are a number of private houses built of the same material, some of them reputed to be upwards of 200 years old and certain of them having considerable architectural merit.

[Headnote: "Substantial and Cool"]

(_Extract from "The Farmers' Handbook," issued by the Department of Agriculture, New South Wales, 1911_)

+"Adobe," or Sun-dried Bricks+

"As their name implies, these buildings are constructed of sun-dried, but unburnt bricks. For buildings of this character, material like clay, which is unsuitable for pise-work, can be used. The bricks are made in a wooden mould, and are 16 in. long, 8 in. wide, and 6 in. thick. A man can mould about 100 per day. They are laid in a similar manner to other bricks, the mortar used being wet loam, or even the material of which the bricks are made. The cost of making and laying is estimated at about 15s. per 100. Buildings constructed of these bricks are substantial and cool, and very similar in character to pise buildings.

"A school-house built of these bricks eighteen years ago by Mr. Nixon, of Reefton, is still in an excellent state of preservation; in fact, little, if any, the worse for wear, despite the fact that walls are unprotected by verandahs or overhanging eaves. During its existence it has had, first one coat of oil-paint, and later a coat of coloured limewash."

"Clay lump," then, is one of the many good old building methods that needs no proving, but only revival and perhaps improvement.

APPENDIX

I

WHITEWASH

Whitewas.h.i.+ng has been frequently referred to in the foregoing pages as the most suitable treatment for the exterior of chalk and earth buildings.

There is, however, a certain prejudice against lime-whiting amongst both owners and occupiers, owing to the frequent renewal that its adoption usually implies.

With a view to removing this drawback from a treatment otherwise so effective, the following recipes are suggested as improvements on the usual practice.