A very common method of forming partitions, and even roofs in some of the agricultural districts in Hampshire, is first to put them up with strong wattle hurdles. They are double the size of the common hurdle, and made of a thicker material. When in their place, they are plastered over with concrete, and made about four inches in thickness; they very often require repair. It is said that concrete walls are subject to contraction and expansion, and speedily show vertical cracks at intervals, which in our damp climate would soon permit the wet to enter. There can be no question as to its strength as a building material, as some experiments conducted by the Institute of British Architects gave the following results—viz., “Concrete composed of two parts of lime, thirty-six parts of sand, and five parts of cement, can resist a crushing weight of four tons to the square inch, being twice the strength of Portland stone, eight times the strength of Bath stone, and sixteen times the strength of brickwork.”
In constructing cottages with concrete everything depends upon the goodness of the cement and the care with which it is used. The occupiers of these cottages are frequently their own operators; the work is generally too speedily performed, and the consequence is that the fruits of their labour are in most instances of but short duration.
For obvious reasons it is necessary that the greatest economy should be observed in the construction of peasants’ cottages, and for these reasons the apartments should always be on the ground floor, which will render it unnecessary to build them more than eight or nine feet high. Where mud walls are introduced, the lower they are made the better, in which case they should be made to batir on the outside so as to resist the pressure of the roof, the covering of which should project as much as possible, to throw off the wet and protect the walls. The chimney flues in these clay and concrete walls are formed of drain-pipes, which answer admirably. These humble dwellings should be paved with brick-on-edge paving laid on sand, which is much warmer, and more conducive to health than any sort of rough flagging, plaster, mud, or concrete floor. The latter, although much cheaper, can never be made to look clean. Foundations of clay or concrete walls should be of brick a few courses above the surface, and the walls when dry should be covered with a thick coat of plaster consisting of lime and sand, or what is still better, a coating of good Portland cement. This ought constantly to be kept perfect, as everything depends upon the goodness of the work. Concrete improperly mixed is not so strong as brickwork, but is mere rubbish; but when perfectly done it hardens with age, becoming like stone, impervious both to wet and frost.
Materials can be found in every locality. One of the principal constructors using such, Mr. Tall, who works with an excellently contrived apparatus, thus describes them:—“Clay, which may be burnt into ballast easily and cheaply, and is a most superior material for concrete; gravel, stone, crushed slag from furnaces, smith’s clinkers, oyster-shells, broken glass, crockery, or any hard and durable substance. Where sandstone or any flat stone is to be found, walls can be built even cheaper than of gravel concrete, as a labourer can break the stone.” He gives the proportions of materials used in houses then being constructed at Gravesend, as follows:
| £ | s. | d. | |
| 7 yards of burrs from brickfield, at 5s. | 1 | 15 | 0 |
| 7 yards of gravel stone, at 3s. | 1 | 1 | 0 |
| 1 yard of Portland cement, 16 bushels to the cubic yard, at 2s. | 1 | 12 | 0 |
| Labour, at 2s. per cube yard | 1 | 10 | 0 |
| Total | £5 | 18 | 0 |
Three cubic yards of concrete will build 60 yards of 9-inch work, at a fraction under 1s. 11d. per yard.
Concrete cottages have been built at Setting, in Kent, under Mr. Adkins, architect, that cost only 105l. per pair; the ground floor contained two rooms; with the usual larder and closets, and the upper floor three rooms and a cupboard; these cottages had gabled fronts and were picturesque in character. It would be an extra expense over the common method to construct floors and roofing of concrete; the advantage to be gained would be their fire-proof character.
In superior buildings the high tenacious power of good cement is repeatedly, it may be said commonly taken advantage of in the construction of roofs. These are formed by cementing plain tiles, and they have considerable strength. Roofs of 12 feet span, constructed in segmental form, rising three feet, and only of three plain tiles in thickness, successfully resist great pressure, and are durable in a very superior degree; but they require to be well tied in, and formed between iron girders connected together with iron tie rods, otherwise they sink and force out the walls. Roofs of cemented tiles have been constructed from 30 to 40 feet span, and have been found to answer well; hoop-iron bond, laid at intervals between the tiles, is a great advantage. The tenacious power of good cement was proved in a very high degree a few years ago by Mr. Brunel, in the construction of two semi-arches built of brick, springing from a pier or abutment 14 feet in height. One extended 50 feet in length, the other 38; the rise of the arches was 10 feet, the width only 4 feet 6 inches; a weight of about 40 tons was suspended to the extremity of the shorter arch without breaking it.
The result of this test proved that arches of 200 feet or 300 feet span, and probably more, might be constructed in the same manner at very moderate expense, without centering. Iron-hoop bond is said to nearly double the strength or holding power of the cement. Flat experimental beams have been constructed of brick and cement, with hoop-iron bond laid horizontally between the joints or courses of the brickwork, which have given equally extraordinary results.
Concrete for walling was extensively used in England at the beginning of the present century; it got into bad repute through failure of a river wall at Woolwich, where it was either badly done, some mistake was made, or it was unsuited to the position. The wall was constructed of blocks of concrete cast in moulds, and submitted to pressure while setting; a coating of fine stuff being applied for the sake of appearance, ample time having been allowed for the blocks to set and harden before use. The blocks were 1 foot 6 inches high, the binders and stretchers in the course being each 2 feet 6 inches long, the bed of the former being 2 feet, and of the latter 1 foot; the wall was built upon piles, its height above the piles being 24 feet; the thickness at bottom was 9 feet, at top 5 feet with a batir in front of 3 feet in 22.