TIN ROOFS 251 



tile among which book tile, Spanish tile, pan tile and Ludowici tile 

 are well known. Tiles are also made of glass and are used in the place 

 of skylights. 



Tiles may be laid (i) on plank sheathing, (2) on concrete and ex- 

 panded metal or wire lath sheathing, or (3) may be supported directly 

 on angle sub-purlins as shown in Fig. 87. Tiles are laid on sheathing 

 in the same manner as slates. 



The roof shown in Fig. 87 was constructed as follows: Terra- 

 cotta tiles, manufactured by the Ludowici Roofing Tile Co., Chicago, 111., 

 were laid directly on the angle sub-purlins, every fourth tile being se- 

 cured to the angle sub-purlins by a piece of copper wire. The tiles were 

 interlocking, requiring no cement except in exceptional cases. The tiles 

 were 9 x 16 inches in size; 135 being sufficient to lay a square of 100 

 square feet of roof. These tiles weigh from 750 to 800 Ibs. per square, 

 and cost about $6.00 per square at the factory. Skylights in this roof 

 were made by substituting glass tiles for the terra-cotta tiles. This and 

 similar tile has been used in this manner on a large number of mills and 

 train sheds with excellent results. 



Tile roofs laid without sheathing do not ordinarily condense the 

 steam on the inner surface of the roof unless the tiles are glazed, al- 

 though several cases have been brought to the author's attention where 

 the condensation has caused trouble with tile roofs made of porous 

 tiles. Anti-condensation roof lining should be used where there is dan- 

 ger of excessive sweating, or a porous tile should be used that is known 

 to be non-sweating. . The cost of tile roofing varies so much that general 

 costs are practically worthless. The reports of the Association of Rail- 

 way Superintendents of Bridges and Buildings give the cost in New 

 England as from $30.00 to $33.00 per square. 



Tin Roofs. Tin plates are made by coating flat iron or steel sheets 

 with tin, or with a mixture of lead and tin. The former is called 

 "bright" tin plate and the latter "terne" plate. Terne plates should not 

 be used where the roof will be subjected to the action of corrosive gases 

 for the reason that the lead coating is rapidly destroyed. Plates are 



