Installation Features

Ridges

There are two common methods of finishing the ridge of the roof. These are usually known as the "Saddle Ridge" and "Comb Ridge" but each may have other names and certain variations in laying according to local practice. In Figure 16 are illustrated two types of saddle ridge which are known respectively as the "Saddle Ridge" and the "Strip Saddle Ridge." In the first of these, the "Saddle Ridge," the regular roofing slates are extended to t he ridge so that pieces of slate on the opposite sides of the roof butt flush. On top of the last regular course of roofing slate at the ridge is laid another course of slate called the "Combing Slate" and the pieces on the opposite sides of the roof butted flush. The combing slate is usually laid with the grain horizontal and should be of such width that the exposure or gauge of the roof is maintained approximately uniform. For example if 20" x 12" slates are used on the roof with an 8 1/2 exposure, 12" x 8" slates laid horizontal could be used on the ridge. It will be noted in Figure 16 that the combing slates overlap and break joints with the underneath slate. In this way all the nails in the combing slate are covered by the succeeding slates except the nails in the last or finishing slate on the ridge and these nails should be covered with elastic cement. In Figure 16 where only two nails are used in each slate. The end of the slate which is not nailed should be held in place by elastic cement. The joints on top of the ridge formed by the butted edges of the combing slates should be filled in with elastic cement when subject to heavy rainfall. Some roofers do not use any elastic cement on either the hips or ridges, but this practice is not recommended except under favourable climatic conditions. The nails should be arranged to go between the joints of the slate immediately below. In some parts of the country it is customary to clip the upper edges of the last roof slate as shown in the drawing, Figure 16, Plate 1. Many architects prefer to keep the grain of the slate vertical, using the same type of ridge with top or combing slate of the same width as the regular roofing slate and the length the same as their exposure. In such cases the starting slate could be a "slate and a half" in width rather than a "half slate."

Another type of saddle ridge is that known as the "Strip Saddle Ridge." This ridge is laid in a similar manner to the above except that the combing slates do not overlap but butt flush and each combing slate has four nails. The combing slate may be the same width as the regular roofing slate or narrower as the designer may wish. The nails should be covered with elastic cement and the edges of the combing slates sent in elastic cement as shown in Figure 16.

The "Combing Ridge" is laid in the same manner as the "Saddle Ridge" except that the combing slate of the north or east side extends beyond the ridge line as shown in the detail, Figure 16. This extension should not be more than 1". This type of ridge may be laid with the combing slate having a grain vertical or horizontal. In either case, the edge of the slate should be set in elastic cement, as shown, and the nails covered with elastic cement. If the top or combing course is projected 1/16" to 1/8" above the under top courses, it will be more easily filled with elastic cement.

A variation of this type of ridge is known as the "Coxcomb Ridge" in which the combing slate alternately project on either side of the ridge.

It will be noted that in Figure 16 the top courses of the regular roofing slate have the edges set in elastic cement. This is done to avoid their lifting under action of the wind and should in no sense be constructed as being necessary from the standpoint of weather-proofness.

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Hips

There are several methods of forming hips on slate roofs, some of which are illustrated in Figure 22. These are the ones most common in all sections of the country although they may be known by other names than those given herein.

The "Saddle Hip" may be formed by placing on the sheathing forming the hip one of two plaster lath or a 3 1/2" cant strip and running the roofing slate up to this strip. On top of the cant strip and the slate are laid the hip slates which are usually the same width as the exposure of the slates on the roof, although they may vary in width on different classes of work.

It will be noted in the detail Figure 22, Plate 1, that the four nails used to fasten the hip slate to the roof are driven into the cant strip and do not go between the joints of the slate. The heads of these nails are then covered with elastic cement and the lower part of the next slate bedded therein as shown. Elastic cement is also placed on the joint between the roofing slate and the plaster lath on the peak of the hip before the hip slates are laid. A variation of the "Saddle Hip" is known as the "Strip Saddle Hip" which is used on less expensive work and may be formed of narrower slates laid with butt joints which do not necessarily line up with the course of the slate on the roof.

Another type of hip is that known as the "Mitred Hip." In forming this type of hip the slates forming the roof courses and the hip are all in one plane as is shown in Figure 22, Plate 2. The hip slates should be cut accurately to form tight joints and the joint should be filled in with elastic cement. The nail holes should be so places as to come under the succeeding hip slate.

A variation of this type of hip is that known as the "Fantail," shown on Figure 22, which is laid in the same manner as the "Mitred Hip" but which has the bottom edge of the hip slate cut at an angle to form a fantail.

Another very popular type of hip is that known as the Boston Hip. In this type of hip the slates are woven in with the regular courses of the roofing slates, as shown in the detail. The nails are then covered with elastic cement and the lower part of the succeeding slate bedded therein.

It is sometimes recommended that metal or slip flashings be woven in with each course of "Mitred Hips" but this is usually unnecessary if proper care and workmanship are exercised in cutting, fitting and bedding the hip slates. There are some roofers who do not use elastic cement on the hip slates and secure satisfactory results.

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Valleys

Of the two methods of forming the valleys the first, and without doubt the more satisfactory, is the open valley. The second, known as the closed valley, is considered by many to be the more pleasing in appearance and is much used on high-grade work. Variations of the closed valley, frequently used in connection with the Graduated or Textural roofs, are the "round" valley and the "canoe" valley.

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Open Valley

The open valley is formed by laying strips of sheet metal in the valley angle and lapping the slate over it on either side, leaving a space between the slate edges to act as a channel for water running down the valley angle. The width of the valley, or the amount of space between the slate edges should increase uniformly toward the bottom. The amount of this increase, or taper, has been determined as 1 inch in 8 feet. For example, in a valley 16 feet long, the distance between slates will be 2 inches greater at the bottom than at the top, as the width increase at the rate of 1/2" in 8 feet on each side of the valley. This permits a uniform width of about 2/3 the width of the slate under the slate adjacent to the valley. The difference in width or taper allows the slate to be laid closer to the valley at the upper than the lower end and takes care if the increase in water received. This tapering of the valley also has the very practical effect of allowing any ice which may form to free itself and slide down as it melts.

This increase width in the valley must be allowed for in placing the flashing strips. Valley flashings are generally laid in pieces up to 8 feet long. The best theoretical manner of taking care of the taper would be, of course, by tapering t he sheets. As this involves considerable additional expense in labor and material it is often more practical to use sheets shorter than 8 feet and increase the width of each sheet an amount sufficient to take care of the taper. This increase in the width amounts to 1/8 of an inch per foot. The increase in the widths of succeeding sheets of various lengths necessary to take care of this taper is shown in table No. 3. Figure 23 shows the method of installing the sheets.

The slate should start 2" each side of the valley center at the top and should taper away from the center at the rate of 1/2" for each eight linear feet. The metal flashing should be sufficient width to extend up under the slate not less than 4" (preferably 6" to 8"), and as far as is possible without being punctured by the slating nails.

Where the two roofs forming the valley have considerable difference in slope or the roofs are much different in size and cause a large variation in the volumes of water delivered into the valley, the metal should be crimped or made with a standing seam to break the force of the water from the steeper or longer slope and prevent its being driven up under the slate of the opposite side.

Showing increase of widths of untapered sheets in a tapered valley.

Condensation forming on the underside of valley flashings, when not free to run off or evaporate, may attack the metal. It is therefore recommended that the felt be omitted under metals if other than copper is used. If felt is omitted under other metals they should be well painted on the underside.

For inexpensive roofs as provided for in the specification for a Standard Roof the copper for valleys is laid flat without crimps or cleats. For high-grade work the copper sheets should be secured to the roof boards and over the felt with metal cleats from 8" to 12" apart. The edge of the sheet is turned over 1/2" and the bent end of the cleat hooked under. The cleat is then nailed to the roof boards with two nails and the cleat bent over to cover the nails. A method sometimes used on wide valleys with the best work is to fold the metal 4" or 5" from the valley line and 3" from the cleat fold. This is known as "Fold-over" flashing.

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Closed Valley

The closed valley is formed with the slate worked tight to the valley line and pieces of metal placed under the slate as shown in Figure 23. The size of the sheet to be used is determined by the length of the slate and the slope of the adjoining roofs. Each sheet should extend 2" above the top of the slate on which it rests so that it may be nailed along the upper edge of the rood sheathing without the nails penetrating the slate. Each sheet should be long enough to lap the sheet below at least 3", and should always be set back of the butt of the slate above so that it will not be visible. These sheets are separated by a course of slate. Each sheet must be wide enough so that the vertical distance from the centre of the valley to a line connecting the upper edges of the sheet will be at least 4". The dimension depends upon the nailing of the slate which should not penetrate the sheets.

Some roofers form the sheets with a center crimp (Figure 24), thus stiffening them and forming a straight line to which to set the slates, and preventing water from one slope forcing its way above the sheet on the other slope.

Another method of forming a closed valley is shown in Figure 24. The sheets are laid in long pieces directly on the paper or felt covering the roof sheathing before the slate is laid. They may be of any desired length and should lap in the direction of the flow at least 4". They should be nailed about every 18" along the outer edge, and care should be take to avoid penetrating the sheet when nailing the slate.

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Round Valley

The round valley forms a pleasing transition between two intersecting lopes when used in connection with the Graduated or Textural roof. However, if not properly laid out it will produce disaster and mar an otherwise beautiful roof. For this reason its laying should be entrusted only to do this particular work. It requires the most careful workmanship and experienced knowledge of the problem to secure a job that will be both pleasing in appearance and water-tight.

Primarily the round valley requires a suitable foundation to establish the general contour. The method of building this foundation is described under sheathing and roof boards on page 40.

The valley slates must be at least 4" longer than the slates used in the corresponding courses of the roof. The sides of the slates must be trimmed to the proper radius and the tops shouldered to make the slates lay flat.

The round valley slates are sometimes bedded inelastic cement. If proper care is used in the trimming and fitting, no flashings should be necessary. Where the workmanship is not dependable, flashings of metal or prepared roofing cut to the proper radius should be used as a precautionary measure. Flashings should always be used wherever ice may form.

The radius of the round valley starts as a maximum at the eaves and gradually diminishes to practically zero at the ridge. For appearance, as well as to facilitate laying the valley slates, the distance across the eaves should not be less than 26". If the roof condition will not permit this, the "canoe" valley should be used.

The canoe valley is a variation of the round valley and is laid in the same manner except that the radius at the eaves and ridge is practically zero. The radius is gradually increased until it becomes a maximum halfway between the eaves and the ridge.

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Eaves and Gables

The under-eave slates should start on a cant strip of suitable thickness, depending upon the thickness of the slate, to enable the second course of slate to be correctly laid. In the case of a cornice, this slate should project about 2" beyond the cant strip, sheathing or finishing member. The length of the under-eave slates is found by adding 3" to the exposure being used on the regular slates. Thus, if 16" slates are used, the exposure is 6 1/2" and the size of the under-eave slate required is 9 1/2". Half slate are sometimes used, or roofing slates of the proper width may be laid horizontally. If the first course is 3/4" in thickness, used 3/8" slates for the under-eave course or 1/4" slates if the starters are 1/2", although the under-eave and first course are sometimes made the same thickness.

The first course of slate is laid over the under-eave course with the butts of both courses flush, and the joints broken.

When changing from a roof of flat slope to one of steeper slope as in the case of a Gambrel roof, the slate of the upper and flatter roof should project 2" to 2 1/2" beyond the steeper roof below. A cant strip should also be used upon which to start the slate of the roof of lesser slope the same as at the eaves.

At the gables the slate should overhang the finishing member of the verge board not more than 1/2". Where close-clipped gables are used or the construction is such that the gable slates have ample nailing, this dimension may be increased, but the projection ought not to be too great for good appearance. Also there are many interesting ways to lay "Gable end" or "Barge" slates under regular courses along gable ends where shadow effect is desired. Ways and means of using and securing all gable end slates depends on type of construction.

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