This section is from the book "A Treatise On Architecture And Building Construction Vol3: Stair Building, Ornamental Ironwork, Roofing, Sheet-Metal Work, Electric-Light Wiring And Bellwork", by The Colliery Engineer Co.. Also available from Amazon: A Treatise On Architecture And Building Construction.
127. The clay used in the manufacture of tiles is composed of aluminum and silicic acid, forming two-thirds of its bulk, with about 10 per cent. each of water and quartz, and very small quantities of potash, titanic acid, and oxide of iron. To prepare the clay for use, it is weathered, which means exposing it to the frost or sun, then mellowed or allowed to stand for a period, tempered by additional working of the clay, plugged, and cleared from stones. It is then ready for molding, after which it is burned in a kiln, glazed, and fired.
128. Salt-glazed, vitrified tile are subjected to intense heat, the glazing being accomplished by throwing salt on the tile in the fire, creating a vapor which unites chemically with the clay and forms a glazing which is affected by neither gases, acids, nor steam, and is practically indestructible. Slip-glazed tile are what are known as firebrick clay tile; they are very porous, and are glazed with another clay known as slip, which is applied under heat; the slip, however, being a foreign body is liable to chip and scale off. For this reason, vitrified tile should always be used in preference to the slip glazed.
129. The styles of tile manufactured are very numerous; they are, however, generally of the interlocking pattern, and made so that they may be laid either on boarding or on battens. The following varieties are generally used: the plain surface tile, with the eave hips; ridge or cresting tile; and finial to suit. Shingle tile are called square, round corner, round end, hexagon, octagon, scallop, Gothic, Grecian, and Persian, and are shown in the order named in Fig. 102. Those used for laying on boards are flat, as at a, with two nail holes in the upper end, and those for hanging on lath have the rib or lug b cast on the back, as well as having the nail holes. The French tile shown in Fig. 103 (a) may be used for laying on boards or battens; the Roman, Fig. 103 (b), for boards or battens. The modern Spanish tile is shown at (c), and the old Spanish, at (d), Fig. 103.
In Fig. 104 (a) is shown the Corean or Oriental ridge tile to be used with modern Spanish tile shown at (b); the eaves or starter tile is shown at (c). Ridge tile should be special, and when so made, the wing of the ridge takes the form of the tile at its lower edge. Eaves tile may be made with antefixas, as shown at (d), Fig. 104, which enrich the appearance of the eaves and take the place of the plain finish.
These tiles are sometimes inserted at intervals on the roof to act as a snow guard. Hip-roll tile [see Fig. 105, (a), (b), and (c)] are overlapped 3 inches when laid, while the roll tiles shown at (d) and (e) have lap joints cast on them; these tiles are secured to the wood hip roll by nails at the lap.
Plain overlapping cresting, or ridging, is shown at a, Fig.
106, and consists of rolls and covers with a plain cresting cast on the cover tile. At (b) and (c), Fig. 106, are shown two styles of lap-joint ridge cresting.
At (a), Fig. 107, is shown a ridge roll made to receive the tile and also having a lap joint, and at (b), an ornamental ridge cresting with lap joint.
At (a) and (b), Fig. 108, are shown two styles of gable finials. At (c) and (d) are shown two hip finials - one with plain wings and the other with wings made to receive the hip-roll tile, the center tile of the front slope, and the first continuous row of tile of the side pitches.
130. The thickness as well as the length and breadth of tile varies; they run from 3/8 to 3/4 inch in thickness, from 3 to 9 inches in breadth, and from 10 to 16 inches in length; the 3/8-inch thickness is generally used.
131. There are four methods of securing tiles to the boards or battens: (1) by hanging with oak pegs as shown in Fig. 109 (a); (2) by nails as at (b); (3) with a rib or lug and nails as at (c); and, (4) as shown at (d), with a rib or lug and also by a wire loop, which is nailed to the lath or batten.
Rendering is used with flat tiles, and torching and shouldering with all tiles in very exposed places, or on flat-pitched roofs; under ordinary conditions, however, these processes are not necessary. When used, they should be applied in the same manner as described for slate roofing.
The roof should be prepared to receive the tile by covering the rafters with either boards or battens, as the kind of tile to be used requires. If boards are to be used, sheath with plank 1 1/4 to 1 1/2 inches thick and 6 or 8 inches wide, tongued and grooved, and laid on diagonally, well nailed at each bearing and at the edges to prevent curling.
Tilting fillets should be nailed at the eaves, valleys, gutters, gables, etc., as described for shingle roofing. When battens or lath are used, especial care must be taken to see that the proper distance is secured between the lath for the tile to be used, and that the lath are horizontal to the eaves, so that the vertical joint of the tile will be at right angles to the eaves. If the tiles are laid on boards, the roof should be covered with two thicknesses of single-ply or one thickness of double-ply fibrous roofing felt, and after the felt has been applied, the gutter and other flashings should be constructed - as described under "Shingle Roofing" - and put in place.
132. The gutter flashing should be of 16-ounce copper, well nailed with copper nails over the eaves tilting fillet, and locked to the gutter proper with a lock seam unsoldered; or it may be turned down over the upstand of the gutter. The first method is used for a gutter nearly level with the eaves, and the second when the gutter is slightly below the eaves.
For valley gutters, 10-ounce copper can be used in 6-foot lengths. It should be laid with a lock seam, fastened to the roof boards with cleats, soldered and sweated on the back of each length, and nailed with copper nails to the roof back of the valley tilting fillets, or screwed down with copper screws. The valleys should be 20 or 24 inches wide.
The hips do not require to be flashed. A wooden hip fillet as at a, Fig. 110, of sufficient height to receive the tile and give it bearing, is attached to the sheathing, and to this fillet the hip tile is secured.
Where a roof comes against parapet, or gable walls, the junction should be flashed with 14 or 1G ounce copper, nailed to the roof back of the tilting fillet. The flashing should be allowed to lap on the roof a distance equal to the width of a tile over the fillet, and should be carried up against the wall at least 7 inches. From the under side of the wall coping, or from a raglet cut in the wall, a lead apron should overlap the copper upstand at least 3 inches, and should be secured to the wall with lead plugs.
133. The ridge does not require flashing, but should be prepared to receive the tile ridge roll in the same manner as was shown for the hips.
Where the tile come against the wood hip roll, they should be cut off to the proper angle and bedded in elastic cement. The valley tile should be made at the works, to conform with the proper angle of the roof, and should have closed ends. Around all chimneys and other openings in the roof, as well as at the finishing course along the ridge, the tile should be well bedded in slater's cement.
Where the ridge tiles have a very deep wing, they should be specially cast with a lap joint, and should be laid in courses the same as the tile. See (a), Fig. 111. They are sometimes built up of flat pieces of tile, as at (b), Fig. 111, with rabbeted joints, and laid with the vertical joints broken; the former tile is preferable.
Very heavy hip or gable finials should be well braced with brass or galvanized-iron rods, and the sections of terra-cotta finials should be securely wired or anchored to the braces, and well cemented. If necessary, a wood cradle should be built on the roof to receive the finials.
The finials on hips and ridge ends may be secured with a tripod form of brace. For a vertical finial the tripod may be made and secured to the roof as shown in Fig. 112, the ends of the iron being held in place with brass or galvanized-iron screws. For an overhanging hip finial the brace may be constructed as in Fig. 113, the top of the rod being carried to the ridge of the finial. Where the finial is on the apex of a tower, the brace may be constructed with a gal-vanized-iron pipe of dimensions to suit the size and shape of the finial, and stiff enough to resist the wind pressure. The construction of such a brace is shown in Fig. 114.
134. A roof may be covered entirely with ornamental roofing tile, or they may be used at intervals among flat tile to break the monotony of the system. When mixed with the plain tile, they may be arranged in pattern or figure shape, but care must be taken to retain uniformity of color in both kinds, as mentioned in "Slate Roofing."
135. The tiles for conical roofs must be made to suit the requirements of each case. It is, however possible, with some varieties of tile, to use a uniform size for four or five courses, or tiers, and a smaller one for the next four or five courses, and so on until the base of the finial is reached.
Shingle tile may be cut on the sides so as to make them conform with the radial lines from the apex, in the same manner as was described for slate and shingles. If, however, the butt of the tile is formed with a pattern, this method cannot be used, and special tile must be made. The eave tiles and the upper courses adjacent to the apex should be well bedded in slater's cement.