may have to be sunk. If this well is to provide drinking water for the house in addition to being used for all purposes in the stockhouses it is desirable-nay, even necessary for it to belong to the type known as 'deep,' which means that a water-bearing stratum of rock must be reached and the surface and subsoil water excluded. A shallow well derives its supply of water from the surface and immediate subsoil, with the result that the water obtained is very little dissimilar to rain-water, whereas the supply from a 'deep well is pure and 'hard.' Where it is possible to supply two or three farms from one point and a suitable stream can be used in the near vicinity an hydraulic ram is one of the cheapest, most effective, and satisfactory methods of supply

The cost of the necessary buildings for a fair-sized small holding of about 50 acres should not exceed £300-£350 for the house and £400-£450 for the other buildings, otherwise the tenant will have, for economic reasons, to be charged a rent greater than his holding warrants.

The drawings given herewith are for a general farming holding of about 50-60 acres, and will give a clear idea of the method of construction advisable in this class of work. It will only be necessary to alter the internal accommodation to suit the particular type of produce in which the tenant intends to traffic for a living. An inclusive method of working out the approximate cost of these buildings is by calculating the cubical contents throughout including the covered yard, and reckoning an average of 21d. per cubic foot.

50895 cubic feet at 24d. £530 38. 1d.

CHAPTER XXIX

STEEL ROOF TRUSSES

ALTHOUGH it is possible to substitute steel for timber in roof trusses, no matter how small the span, it will generally be found more satisfactory to employ timber for all spans not exceeding 35 feet. From that measurement upwards the advantage in using steel increases for the following two important reasons:

1. When the span is greater than 35 feet, the timber members of a roof truss are necessarily large in scantling and therefore expensive.

2. Large scantling means a ponderous and somewhat overwhelming appearance, whereas, even in very big spans, a steel roof truss can be constructed so as to present quite a light effect.

Another distinct advantage which steel has in such work over timber is the possibility of construction with a camber, i.e. the vertical distance from the level of the top of the template to the underside of the tie bar, giving a great deal more head room. This is impossible in a timber roof truss of considerable span as the tie beam has to rest upon the templates at a level which must be maintained from wall to wall.

The covered yard, therefore, is in all probability the only span throughout the buildings for a farm of reasonable acreage where any great advantage will accrue by the use of steel in the roof trusses. This span will, of course, vary with different plans from about 35 to 50 feet. Taking 40 feet as a fair average span, the accompanying drawing of a steel roof truss with all its details furnishes a typical example, in design and scantling, of a suitably constructed truss. It will be noticed that the principal rafters and struts are of T-section, the former being a little larger than the latter. The king rod and the smaller queen rods are simple bars of circular section. At the points where the rods and struts are fixed to the tie rod, which is also of circular section, the latter is forged into nearly rectangular bulges through which bolt holes can be drilled without weakening the rod as would be the case without the extra width provided by the bulge. The heads of the king and queen rods are forged with eye-holes to provide the necessary fixing position for bolts. For as far as the struts lie up

against the web of the principal rafter the flanges can be cut away. Similarly at the feet, in order to secure the struts to the bulge provided in the tie rod, the web is cut away and the flange bent upwards exactly to suit the angle which the camber gives to the tie rod. At the junction of the principal rafters and the head of the king rod, a gusset plate is inserted whose upper edges fit in closely underneath the flanges of the principal rafters, providing a very satisfactory and secure fixture for the three members at the apex of the truss. To provide for the fixing of the timber portion to the trusses as they pass over, short pieces of the angle iron, equal in length to the width of the flange of the principal rafter, are first bolted in position, the purlin afterwards being bolted to the vertical parts of the angle irons. The purlins are, of course, placed immediately over the struts. Similar provision is made for the fixing of the ridge board, except that it is supported on both sides by short lengths of angle iron.

The whole roof truss springs from shoes to which the feet of the principal rafters and the ends of the tie rod are bolted. These thoes are set on stone or concrete templates built into the walls, and secured thereto by means of bolts previously let in with cement. As will be understood, such trusses vary in weight according to the sizes of the various members, and although it is possible to estimate fairly accurately the total cost from the total weight, the cost is more correctly found by working out the individual weight of each type and size of member and applying the price per cwt. as quoted in merchants' price-lists. The cost per cwt. varies according to the amount of labour required to produce steel members of different sections. Thus, bars of circular section are not as expensive, weight for weight, as those of T or H section.

The small single line diagrams will show a few of the trusses of different construction applicable to certain spans. All but those with a camber have been omitted.

The total cost of steel roof trusses, made up as shown in the drawing, and including all necessary parts, junctions, &c., and fixed complete is 278. 6d. per cwt.

INDEX