1 66 ENGINEERING ON THE FARM 



this size These are given color by chips of slate or fine 

 sand of an even color rolled into the surface. They are 

 very durable and the color is fast. 



Asbestos shingles. An asbestos shingle is made after a 

 patent process. The size is usually i2"X i2 ,, XJ4 "• The 

 variety of color is not great. They are a little more expen- 

 sive than wood and asphalt, but are more durable. 



Tin and galvanized shingles. Tin and galvanized iron are 

 offered in plain shingles and various stamped shapes, in 

 imitation of some of the older roofing tiles, but are com- 

 paratively short-lived. 



Tile shingles. Roofing tiles, which are made of clay or 

 concrete, are heavy and used only on the best of buildings 

 where permanent construction is more important than low 

 cost. 



Slate shingles. Slate, which is to be had in several sizes 

 and two or three thicknesses, is also too heavy and too expen- 

 sive for most buildings. Tile and slate will weigh from 750 

 to 1000 pounds per hundred square feet laid on the root. 



Paper roofing. Among the cheap root coverings is the 

 paper roofing or rolled roofing. These come in weights 

 designated as 14, i, 2, 3 ply, and extra heavy. The widths 

 are 18 and 36 inches. A roll contains enough roofing to 

 cover 200 square feet, including the lap. 



Tar-and-gravel roof. A tar-and-gravel roof is used on roof 

 surfaces that are nearly flat. The expense is somewhat 

 higher than that of rolled roofing, which may be used on 

 flat surfaces, but the life of tar and gravel roofing is usually 

 somewhat longer. 



FINISHING 



Plaster. Real plaster is usually made of sand to which 

 are added hair or fiber and a cement in the form of Portland 

 cement, natural cement, hydra ted (water-slaked) lime, plaster 

 of Paris in its natural state or as a patent plaster such as 

 Keene cement. The oldest combination was lime, sand, 



