This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol1", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
Tiles for roofing purposes consist of thin plates of vitrified clay, and are made in an infinite variety of shapes and sizes. They are usually of a red colour, but can be obtained in practically any shade. The tiles in general use are exhibited in the following table: -
Sizes in Inches.
Weight of each
Tiles required per Square.
Weight per Square.
10 1/2 x6 1/2x1/2
11 x 7 x 5/8
13 1/2x9 1/2x1/2
Plain tiles are made with a slight curve throughout their length, to cause their tails to fit closely against course below, and have small projections called "nibs" at the back for hanging them on to the laths, or holes at the head for nailing, or both.
Pantiles are much used for shed roofs, and are curved as shown in Fig. 295.
Plain tiles are fixed to battens or boards or both, arranged as described for slates in the previous Chapter.
The laths used for plain tiles are either of fir (1 1/4 by 3/4 inch to 2 by 1 inch) or oak (1 1/4 by 1/4 inch), and are made in 5 feet lengths, one bundle of 100 fixed to the rafters with 150 lath nails being required per square of tiling.
The lap used for tiles varies from 3 to 4 inches, according to the size of the tile, the pitch of the roof, and the climate of the locality in which they are used.
The gauge is determined thus -
Gauge = Length of tile-lap/2.
In Fig. 296, 10 1/2 by 6 1/2-inch plain tiles are used, and laid to a 3 1/2-inch lap, so that the gauge = 10 1/2 - 3 1/2 /2 in = 3 1/2 inches.
When tiles with nibs are used they are only nailed every three or four courses on roofs of steep pitch, while when on roofs of flat pitch every tenth course only need be nailed.
Pegs of cast iron or oak are also used for fixing tiles, they being wedged into the nail-holes and hung upon the laths.
Pantiles are laid upon laths with a good bed of hair mortar to keep them in their place. The laths for pantiles are 10 feet long, a "bundle" of 12, secured to the rafters by means of 125 lath nails, being required per square (100 feet super.) of tiling.
Glass tiles of the same shape and size as pantiles are often used for skylights.
The tiling is commenced from the eaves, which are treated in a similar manner to slate eaves, special short tiles being made for the doubling course of the same width as the ordinary tiles, and of a length equal to the sum of the lap and the margin, as shown in Fig. 296. The doubling course should be firmly nailed to a board splayed so as to cause the tail to fit closely against the tail of the course above. The tail of the lower two courses should overhang the gutter, so that rain water may drip clear of the woodwork. The first batten is fixed at a distance above the lower edge of the board upon which the doubling course is fixed, of the length of a tile less the distance of the nail-holes from the head of the tile, and less the amount of overhang.
Fig. 295. Verge Tile.
When a roof terminates as a verge or against a gable, specially made "half" tiles, as at A, Fig. 296, or "tile-and-a-half" tiles, as at B, should be used. The brickwork beneath the verge should be cut to the slope of the roof, and the tiles should be soaked and bedded in Portland cement so as to tilt away from the edge, thus throwing the water on to the body of the roof and preventing the verge from dripping.
When the roof abuts against a gable wall the wet is excluded by means of "lead soakers" or "secret gutters."
Specially made short tiles are made for the uppermost courses of tiles, the length being equal to the length of a tile minus the margin plus 1 inch for the nail-hole, as shown in Fig. 296.
To obviate the necessity of cutting the tiles at the ridge the following simple calculation is made: The lowermost and uppermost battens having been fixed in position, measure the exact distance from centre to centre of these and divide by the gauge. Thus suppose the distance from centre to centre of the two extreme battens is 27 feet 6 3/4 inches, which, divided by the gauge 3 1/2 inches = 95 and 2 1/2 over. If the battens are nailed on starting at the bottom, and working upwards are spaced at intervals of 3 1/2 inches, there will be a gap between the two top battens of 2 1/2 inches, which would necessitate the cutting of an inch off the top tile to keep the margin uniform; but to obviate this, all that need be done is to space the battens a little farther apart. It is clear that the gauge is practically unaltered if 2 1/2 inches is spread out between 94 battens.
Specially made tiles are used for covering ridges, as shown in Fig. 295, and are usually bedded in hair mortar. It is a good plan to bed only the ends of such ridge piece, as this permits the air to circulate beneath, and thus prevents the ridge board from rotting.
Purpose made ridge finials are made for covering the apices of verges and the junctions of ridges, as shown in Fig. 295.
The vertical joints of ridge pieces should be pointed.
In cheap work the edges of the tiles are roughly cut to fit the hips, and the junction is covered with a half-round tile bedded in hair mortar. It is better, however, to use purpose made hip tiles, as shown in Fig. 295.
The most usual way of treating valleys is to stop the tiling of the adjoining roof somewhat short of the valley and to form a lead gutter. Sometimes purpose made narrow tiles are worked round the valley, or purpose made nailing tiles are used, as shown in Fig. 295.
The joints of tiles are sometimes pointed as a further safeguard against the passage of wet and wind, and in good work pulverised tiles are often substituted for sand in the pointing mortar, so that its colour may be as nearly as possible that of the tiles.
Walls are sometimes covered with vertical tiling, for the purpose of throwing off the rain and of maintaining a more equable temperature within the building, the air space beneath the tiles acting as an insulator. If tiles are nailed to the joints of brickwork the gauge is only about 3 inches, which gives a lap of 4 1/2 inches. This makes the work unnecessarily extravagant in tiles. For this reason they are usually fixed to battens or fixing blocks, or else the wall is built with wide joists, as shown at A, Fig. 297, and the tiles are nailed to the joints, the gauge being about 4 inches, which gives a lap of 2 1/2 inches.
When battens are used they are fixed to coke breeze concrete fixing blocks to a gauge of 3 1/2 to 4 inches, but these will decay in time, and should not be used in consequence.
The most satisfactory method of fixing vertical tiling is shown at B, Fig. 297, where fixing blocks 9 by 5 by 1 1/2 inch are built into the wide joints on the face of the wall, the tiles being nailed to the blocks; and if they are ribbed they are hung from the projecting portion of the blocks.
Purpose made tiles are used for the internal and external angles of tile-hung walls, or else the angles are close-cut, with lead soakers inserted beneath the tiles to keep rain from penetrating.
The tiles at the side of openings in tile-hung walls should be solidly bedded in cement, as shown at C, Fig. 297; and those above an opening should be tilted outwards by fixing the two lower courses to battens attached to tilting pieces fixed to the lintel over the opening, as shown at D, the lower course being a doubling course such as is used for eaves.
The sills of windows are usually formed as shown at E, so that the course of tiles immediately below it can be nailed thereto, thus preventing the rain from driving up underneath.
When the tile hanging is carried down to the ground the lower course is tilted outwards, as shown at F, Fig. 297, a cement or stone channel being formed below to carry off the water which runs off the face of the tiles in very exposed situations.