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.
39. Balustrades, like cornices, etc., are constructed either with wooden or with fireproof supports; the kind to be employed will depend upon the construction of the building. Balustrades, pedestals, etc. on non-fireproof buildings are usually backed with, or secured to, woodwork, while those on fireproof buildings are nearly always supported by iron or brickwork.
Fig. 27 is a section through a balustrade which is commonly employed where the cornice deck pitches to the front and the roof pitches to the rear. The bottom rail a extends down to the deck, the metal being flanged over and soldered to the roofing. When the deck over the cornice grades back towards the balustrade, and when the base rail extends down to the deck, it is necessary to solder in some drain tubes to take away the water. This will prevent a pool of water from forming against the base of the balustrade. The trouble, however, with such tubes is that they will become clogged with snow, etc. The best arrangement is to elevate the base rail a distance of 2 or 3 inches above the deck. Roof-cornice decks, in fact, should always pitch back to the roof to prevent rain from dripping over the cornice. When the base rail does not extend down to the deck, the sheet-metal backing is composed of solid timber entirely covered with metal.
To prevent the rail from sagging, wooden blocks which are covered with sheet metal are inserted under the rail at distances of from 6 to 8 feet apart. The coverings of these blocks are bent over at the top and nailed to the under side of the base rail, while at the bottom they are bent out and soldered as a flange to the deck.
The cap rail b is usually made of wood and covered with two pieces of sheet metal, with drips formed at c, c' as shown. The seams are made at the rear.
40. The balusters f are either spun, pressed, or cast. If they are spun or cast, there will be no vertical joints in their length. If they are pressed, they are put together in halves, which necessitates two vertical soldered seams. Pressed metal is generally used on ordinary work because it is so much cheaper than the spun or cast metal. The top member d and the bottom member e of the baluster are usually square. All the different members are securely riveted and soldered together before the baluster is set in position. After the cap and base rails are in place and lined up properly, the balusters, which are hollow and flanged at top and bottom, are pushed into place. The flanges are securely nailed to the under side of b and to the top of a, as shown, the bottom flange of each baluster being soldered water-tight over the nail heads. The top flanges are not soldered, because the drips protect them.
It is generally understood that sheet-metal balusters are strong enough to support the top rail under ordinary conditions ; but in cases where a load is liable to be placed on the cap rail, it is advisable to put a strut inside of each baluster, which will take the load off the metal and prevent the baluster from collapsing.
In fireproof construction the general arrangement is the same, the principal difference being that iron backing is used instead of wood, and the metal is bolted to it in a manner similar to that prescribed for cornices.
41. A pedestal, as ordinarily constructed, is composed of a framework made of 3"x4" timber, spiked to the roof and sheathed, as shown in Fig. 28. The projections necessary for the moldings, etc. are blocked out. In the figure the pedestal is provided with a panel face and a flat back. The sides may be paneled or plain. The dotted lines show the relative position of the balusters a and the cap and base rails with respect to the pedestals.
The sheet metal for the front and sides is made to fit the pedestal and is then put on in one piece. The back piece is then put in place and double seamed to the sides, flanges b, b' being formed at the base and soldered to the deck. The top is then put on and double seamed over a flange, as shown at c, c'. The double seam is shown turned down and finished at c, while it is only half finished at c'. The molding, or projection at d, is returned on the pedestal and miters with the top rail. The base block, in a like manner, returns and miters with the base rail of the balustrade. If a finial or vase is to be set on the pedestal, the connection should be made with a flange at e and should be lock seamed and soldered water-tight.
Corner pedestals are paneled on two sides; this necessitates a vertical seam on the outside and inside corners of the pedestal.
In fireproof construction, the backing for the pedestals is usually composed of brickwork when they are located immediately over the wall head. The sheet-metal covering is then made up in one piece and is slipped down over the brickwork, being secured to the deck with a flanged seam, as shown in Fig. 28. The top sheet, also, is secured in a manner similar to that shown in Fig. 28.
When a tall finial, which requires a support, has to be set, it is advisable to run a tube up through the center of the pedestal and screw the top member of the finial to this support.
When a solid brick backing cannot be obtained, it is necessary to construct a framework of wrought iron, which is thoroughly braced diagonally and bolted to the roof. The metal covering is then placed around the frame, and bolted or riveted in position in the ordinary manner.