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.
Wall or flashing hooks, as shown at (a), Fig. 41, or b, Fig. 42, hold the flashing in place where it lies against the wall, or they are driven over the apron flashing to prevent it from pulling out; they are usually placed at about 16-inch centers.
Wall nails, as shown at (b), Fig. 41, are used for the same purpose, but are not so good, as only the shoulder, or under side of the head, bears against the flashing.
These wall hooks and nails should be of galvanized iron or of composition metal to prevent the corrosion of the metals they hold in place. Tile, shingles, and slate are nailed to the roof with both cut and wire nails. For shingles or small slate, a cut nail (c) or (d), or a wire nail (e), Fig. 41, of a length equal to the thickness of the roof-boards should be used. These nails should be galvanized or tinned. The clean-cut steel nail, with countersunk head shown at (f), is generally used for slate.
The copper wire nail (g)
Is used for tiling, and the size is regulated by the kind of tile used and the thickness of the boarding. The thickness of the tile, plus the board thickness, gives the length. Cut and wire steel nails, galvanized or tinned, are also used for tiles.
For composition roofing, the clout nail (c) and (d), Fig. 41, should be used, with or without a tin collar. Composite nails are preferable for all kinds of roofs where nails are used. The best are made of 7 parts copper and 4 parts zinc. By their use the dangers of corrosion and galvanic action are avoided or reduced to a minimum.
Where flashings are placed in a raglet in stonework, they are held by wood or lead plugs or bats; lead is preferred, as it permits more driving. These bats (see a, Fig. 42) are made up of pieces of lead 1 1/4 inches long by 3/4 inch wide, until a thickness suitable to the joint is formed. They are placed at 12-inch centers, and are driven in and calked in place.
laying tin roofs.
54. The methods for laying tin roofs vary. The flat seam, secured with either nails or cleats, is used on flat-pitched roofs; the standing seam is used on steep-pitched roofs, and occasionally on flat parts of such roofs, known as decks.
Of the first two methods of laying a tin roof, the one in which the seam is secured with cleats is to be preferred, the objection to the other being that the nails make holes in the tin, and as the tin expands or contracts, the holes become larger and the nails work loose.
55. Boarding for the roof should be matched and of even thickness, so that the surface shall be smooth and free from all rough spots or ridges; if possible, the boards should run lengthwise with the current or pitch, that is, the direction in which the water will flow when the roof is completed.
56. Felt paper under tin is of much advantage, and should be used. It prolongs the life of the tin; excludes any injurious vapors, gases, or fumes, which might reach the tin from the rooms below; protects the tin from any injurious substances in the roof boards; and prevents "sweating."
57. The preparation of the sheets for laying, which should be carried out at the tinner's, consists of edging, that is, turning the edges of the sheets to form the seam. The upper and right-hand edges are turned up; the lower and left-hand edges are turned down.
In laying a tin roof, a start should be made at the lower left-hand corner of the roof, the course of which should lock into the gutter seam a, as shown in Fig. 43, or into an eaves flashing. If the gutter is supported by straps, these should also be locked into the same seam.
In Fig. 44 is shown the flat seam roof secured with nails, which are put in as each sheet is laid. These nails should not be spaced further apart than 6 or 7 inches, and should be so placed that the nails of the last sheet will not come over those of the preceding ones.
In a 10" x 14" sheet there will be three nails, as shown at a, Fig. 44; while, by reason of the lock seams, the sheet will be further secured by the adjoining sheets and the nails in them. A sheet 14 in. x 20 in. will have five nails, and one 20 in. X 28 in., six nails. In exposed locations the number of nails should be increased, so that a firm and rigid surface can be obtained.
As shown at a, Fig. 45, the nails are covered by the overlapping edges of the next sheet, and also by the course above. After the tin has been nailed to the roof, the next process is to mallet down the seams; the quality of the roof to a great extent depending on the skill with which this operation is performed. Care should be taken not to break the seams, and to lay them evenly. The horizontal seams make the straight lines, while the other seams break joint, as shown in Fig. 44.
58, Flashings for skylight curbs, bulkheads, etc. are shown in Fig. 46; those for fire and gable walls, with apron or counterflashings, are indicated in Fig. 47.
The curb flashing (see a, Fig. 46) is nailed on top of the curb c at b, is turned down against it to the roof, then carried over the fillet d out on the roof and seamed and locked to the roof tin at the joint e.
The wall flashing is placed in a raked-out joint a, Fig. 47, is secured with flashing hooks, turned down and over the fillet b to meet the roof tin c, and the two are seamed together. The apron flashing d is placed in the joint e and nailed with flashing hooks; it laps over the wall flashing about 4 inches. The joints a and e should be pointed with mastic or elastic cement.
59. The next process is soldering the seams. For joining tin, the solder should be composed of one-half tin and one-half lead. This solder is known and branded as half-and-half. After the seams have been resined, the solder is applied by a flat-bottomed copper of sufficient size to melt the solder and keep it flowing. A small copper should not be used, because it does not hold heat well and produces, in consequence, an uneven seam without soaking the solder back into the crevices. Resin should be used as a flux for soldering tin; acid must not be used, for while it does as well for soldering as resin, it is likely to be driven into the seams and attack the metal.
GO. Fig. 48 illustrates the method of laying the tin with cleats. There are two nail holes made through the sheets, and the manner of fastening the cleat to the roof is such as to permit all necessary contraction and expansion, without injury to the roofing material.
The cleat a consists of a simple strip of tin, from 2 to 3 inches in length, and from 1 to \\ inches in width. One end b is bent to the same shape as the corresponding edge of the plate locking into it. The overlapping edge of the upper sheet covers the cleat. The nail is driven near the opposite end of the cleat, as shown at c, but so far removed as to have no effect on the expansion and contraction of the sheets. In consequence, no strain is produced on the seams. The strips, it may be noticed, are nailed to the board direct, and the next sheets cover them.
61. A standing seam is shown in Fig. 49. The sheets are bent up at the edges, which is done at the shop, the left-hand edge a about 1 3/8 inches, and the right-hand edge b about 1 inch. Between the sheets a cleat a (see Fig. 50) is nailed before the next sheet on the right is placed. The cleat is 2 inches wide and its height is equal to the height of the left-hand standing edge of the sheet of roofing. Cleats should be spaced near together for steep roofs; for decks the spacing is usually the same as in flat roofs, or about 16 inches apart. There should be at least one cleat to each sheet of tin. The horizontal seams, as shown at b, are always flat like the flat-seam roof.
These seams may be either single lock, as at (a), or double lock, as at (b) in Fig. 51. After the metal covering has been put on, the part of the left-hand sheet projecting above the right (see Fig. 49) in the vertical seams, is turned over and down with a seamer, as at c, Fig. 50.
62. Nails for tin roofs of all styles should have a length slightly less than the sum of the thicknesses of the roof boards, the felt and the tin, in order that they may not protrude below the lower surface of the sheathing.
The nails commonly used are similar to slaters' nails. They are thick, some having a slight bulge in the center, and are strong enough to drive through the thickest tin. Neither iron nor tin-coated, but zinc or galvanized nails should be used. The zinc produces a rough surface, tending to prevent the nails from drawing out.
63. For the sake of economy, sheets of 14 in. X 20 in. or 20 in. X 28 in. are generally used for roofing purposes.
One sheet of tin 14 in. X 20 in. covers 235 3/16 square inches, or 1 foot 7 1/2- inches, of standing-seam roof. A box of 112 sheets covers 182 feet 14 inches of roof, allowing 1 inch and 1 1/4 inches for the two side seams, and 1/4 and \ inch for top and bottom seams, respectively. In these calculations, no allowance is made for waste of any kind. One sheet of 14 in. X 20 in. covers 255 square inches, or 1 foot 9 1/4 inches of flat-lock roofing, and a box of 112 sheets, allowing 3/8 inch all round for joints, covers 198 feet 3 inches.