Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/563

Rh AND SLATER-WORK.] BUILDING 501 which is employed in plain tiling. To a roof with pro jecting eaves a wide board is placed over the ends of the rafters; but when the eaves tail into gutters, the gutter-board is made wide enough to receive the eaves-course For light slating it is necessary to board a roof all over with three-quarter inch rough boarding. This is done by the carpenter ; but foi strong heavy slates, fillets or laths or battens are considered sufficient ; and these are laid by the slater himself, to suit the length of his slates. Three inches wide and one inch thick is a sufficient size for them, if the rafters be not more than 12 inches apart. Against gable or party-walls, a feather-edged board called a tilting fillet is laid to turn the water from the wall. A preferable plan, however, is to board all roofs ; it gives a better bed for the slates, and fewer are broken if there be occasion for workmen to walk over them in repairing or in cleaning out the gutters. The expense, too, is but trifling beyond that of the laths. A still further benefit is obtained by bedding the slates in mortar or in hay, which fills up the spaces left by the thickness of the first slate, and with the boarding tends to keep the roof cooler in summer and warmer in winter, a very desirable result for the habitable rooms close under them. Where the roofs are finished with diagonal boarding on purlins without rafters, it makes a very sound bedding for slates. All the slates being gauged to a width, and dressed as above described, and sorted in lengths, they are then taken up to the roof in rotation, beginning with the longest and largest for the lowest courses. The first course the slater lays is little more than half the length of that which is intended to cover it, and is necessary to break the joints at the eaves. This is called the doubling eaves-course ; and the covering eaves-course is brought to the same foot line, completely to cover it. Then to ascertain the gauge : from the length of the slate deduct the bond, which should never be less than 2 inches, and need not be more than 3 inches, and the half of what remains will be the gauge. Thus, if the bond be fixed at 3 inches, and the slate is 2 feet 3 inches in length, the gauge will be 1 foot. This gauge or margin is set up from the foot of the eaves-course at each end, and a line strained to mark it along the whole length, and so on, to the ridge or top. where another half-course is required to complete the work, and that is in its turn secured by a covering of sheet lead with a roll. To a hipped roof care is taken to complete every course up to the angle, by cutting slates to fit its slope; and these are also covered by an overlap of sheet lead with a roll, it being nailed or screwed to the hip rafter, and the head bossed over. Slate ridging with a roll, as fig. 115, or with a groove for receiving an orna mented cresting, is now very usual, and even a common ridge tiling is neces sary to prevent theft of the lead in Fro. 115. Ridge of Roof. some localities. Fig. 11G shows specimens of the orna mental red ridging tiles occasionally used, continuously or some lengths of a plain tile apart. In fig. 115, A, A are the two portions of the slate roll ridging, B being the roll with a hole drilled at each end for the insertion Vraiav ~f FIG. 11G. Ridging Tiles. of a pin to fix the lengths ; C the ridge piece fixed in the head of the king-post D ; E the rafter ; F the lath on which G, the slating, is nailed. In nailing a slate, it must not be strained or bent in the slightest degree, or it will certainly fly in some sudden atmospheric change, to which it is of course constantly liable, even if it escape fracture from being trodden on by the workmen themselves or by others. Copper, being less liable to oxidize from exposure to common causes than any other metal that will answer the purpose, should always be used for slate nails. Zinc is also occasionally used ; and iron tinned and painted nails are sometimes substituted by dishonesty on the part of the workman or builder, or bad economy on that of the proprietor. The French method of fixing slates by means of wire clips which hold the bottom of the slates is unusual in England. A method has lately been introduced of effecting it with lead clips, which is said to dispense with a certain proportion of slates. Each slate is held in some thing of the same manner which the slater now adopts when a broken slate has to be replaced, and the main advantage is supposed to be that the slates are firmer. The mode above described of ascertaining the gauge or margin by the bond, is equally applicable to every sort of roof-covering that is made up of small inflexible parallelo- gramic slabs or tablets ; and it should be borne in mind that the greater the angle is at which the rafters rise, or, in technical language, the higher the pitch of the roof, the less the bond may be, and vice versa. With slabs or tablets that vary in length, too, as slates generally do as they are brought to market, it is the bond which it is of importance to observe ; but if they are of an invariable length, as tiles are, it is sufficient that the gauge or margin be attended to. A very light and neat covering is produced by laying patent wide slates side by side, and covering their joints with slating, narrow slips bedded in putty, the overlap at the ends being no more than the bond is with the usual mode. It is known as patent slating, and was introduced by Mr Wyatt, who never, however, obtained a patent for it. In deed it is in principle the mode which was adopted in ancient Greece in covering the roofs of temples. Neither boards nor fillets are used, the slates bearing from rafter to rafter, which may be 2 feet or more apart, and to the rafters the slates are screwed. The covering slips are also screwed, as well as bedded in putty. Slating of this kind may be laid at no greater elevation than 10, whereas for slating in the ordinary way the angle should never be much less than 25, though large slates with a 3 inch bond, carefully laid and pointed, may perhaps be trusted at a rise of 20. This mode of applying slate is not without the disadvantage attend ing the fixing of any substance that freely takes up and readily parts with heat. In expanding and contract ing, the joints are too often destroyed, and leaks are tho comm on consequence. Thatching is an admirable covering for securing warmth Thatching, in winter and coolness in summer; but it is subject to injury by birds, and to risk from fire. It is still occasionally used in picturesque cottages, arbours, and similar build ings, and was much used for churches in Norfolk and Suffolk. The thatcher requires a common stable fork, to toss up the straw together before being made into bundles; a thatcher s fork, to carry the straw from the heap up to the roof; a thatcher s rake, to comb down the straw straight and smooth ; a knife, or eaves knife, to cut and trim the straw to a straight line ; a knife, to point the twigs ; a half glove of leather, to protect the hand when driving in the smaller twigs or spars ; a long flat needle ; a pair of leather gaiters to come up above the knees, used when kneeling on the rafters ; and a gritstone to sharpen the knives. Wheat straw lasts from 15 to 20 years, and oat straw about 8 years. Reed thatching, as done in the West