There are two kinds of tin-roof coverings in common use, namely, flat seam and standing seam. In the former method the sheets of tin are locked into one another at the edges, and nailed to the roof-boards as shown in Fig. 2. Six or eight 1" wire nails are allowed to the ordinary sheet. The seams are flattened with wooden mallets and soldered water-tight. The seams constitute the weakest part of a flat tin roof, and should therefore be made and soldered with great care. The tinner should not hurry the soldering, for time is required to properly "sweat" the solder into the seams. Resin is the best flux; chloride of zinc or other acids should not be used. A better method of fastening the shifts to the roof is by means of tin cleats about 1 1/2 in. X 4 in. These are nailed to the roof, and locked over the upper edge of the sheet, about 15 in. apart.

Tin Roofing 346

Fig. 2.

* The term penny as applied to nails is a corruption of the original form in which the nails were defined as 3-pound, 4-pound, etc., meaning that 1.000 of the nails weighed 3 pounds, 4 pounds, etc., respectively.

Standing-seam roofing is that in which the sloping seams are composed of two upstands interlocked, and held in place by cleats. They are not soldered, but are simply locked together, as shown in Fig. 3. The sheets of tin are first double-seamed and soldered together into long strips that reach from eaves to ridge. One edge is turned up about 1 1/4 in. and the other about 1 1/2 in. The cleats are placed about 15 or 18 in. apart. When the upstands and cleats are locked together the standing seam is about 1 in. high.

Before laying tin, the uneven edges of the boarding should be smoothed off and the boarding covered with at least one thickness of sheathing paper or dry felt, to form a cushion and otherwise protect the tin. Knot holes in the boarding should be covered with pieces of heavy galvanized iron. Only the best quality of tin should be used, and it should be painted on the under side before it is laid.

The outer edges of the tin should be turned over the upper edge of the cornice, and clasped to a strip of hoop iron; or, where it connects with a metal gutter, the two should be locked and soldered. Where a tin roof abuts a chimney or wall, the tin should be turned up sufficiently to prevent water from rising over it. This upstand should be counter-flashed with sheet lead; and abutting a wooden wall it should be turned up against the boarding, and the siding or shingles laid over it. The tin should also be turned up against all balcony posts, and the edges at the angles well soldered.

Tin Roofing 347

Fig. 3.

The roof should be painted within a few days after it is laid, either with red lead in linseed oil, or a good asphaltum paint, particular care being taken to scrape off all resin before the paint is applied.

There is little or no difference between the methods of laying tin or copper roofing. The most important point to be considered in copper roofing is to have the copper thoroughly tinned before commencing to solder it.

For other data on Tin Roofs, see page 353.