252 ROOF COVERINGS 



covered with tin (i) by the dipping process in which the plates are 

 pickled in dilute sulphuric acid, annealed, again pickled, dipped in palm 

 oil and then in a bath of molten tin or tin and lead ; or {2) by the roller 

 process in which the plates are run through rolls working in a large 

 vessel containing oil, immediately after being dipped. The latter 

 method gives the better results. 



Two sizes of tin plates are in common use, 14" x 20" and 20" x 

 28", the latter size being most used. Tin sheets are made in several 

 thicknesses, the 1C, or No. 29 gage weighing 8 ounces to the square 

 foot, and the IX, or No. 27 gage weighing 10 ounces to the square foot, 

 being the most used. The standard weight of a box of 112 sheets, 14 x 

 20 size is 108 pounds for 1C plate, and 136 pounds for IX plate. Boxes 

 containing imperfect sheets or "wasters" are marked ICW or 1XW. 

 Every sheet should be stamped with the name of the brand and the 

 thickness. 



The value of tin roofing depends upon the amount of tin used in 

 coating and the uniformity with which the iron has been coated. The 

 amount of tin used varies from 8 to 47 pounds for a box of 20 x 28 size 

 containing 112 sheets. 



Tin roofing is laid (i) with a flat seam, or (2) with a standing 

 seam. In the former method the sheets of tin are locked into each 

 other at the edges, the seam is flattened and fastened with tin cleats 

 or is nailed firmly and is soldered water tight. Rosin is the best flux 

 for soldering, although some tinners recommend the use of diluted 

 chloride of zinc. For flat roofs the tin should be locked and soldered 

 at all joints, and should be secured by tin cleats and not by nails. For 

 steep roofs the tin is commonly put on with standing seams, not 

 soldered, running with the pitch of the roof, and with cross-seams 

 double locked and soldered. One or two layers of tar paper should 

 be placed betwen the sheathing and the tin. 



In painting tin all traces of grease and rosin should be removed, 

 benzine or gasoline being excellent for this purpose. A paint composed 

 of 10 pounds Venetian red and one pound red lead to one gallon of 



