316 ENGINEERING ON THE FARM 



The application of rolled roofing is comparatively easy and 

 rapid. Some manufacturers recommend the laying of their 

 roofing horizontally, others up and down the slope of the 

 roof. If this type of roofing is laid upon a tight, smooth 

 sheeting, thoroughly cemented at the joints, it will last 

 from fifteen to thirty years. It may, in some cases, need 

 painting once or twice during that time. These roofings 

 are made of a felt saturated with asphalt gum. The paint, 

 therefore, should be an asphalt paint. Asphalt is black in 

 color and does not make the most attractive roof. Only 

 the heaviest of the rolled roofings should be used on flat 

 surfaces. Chief among the objections to the rolled roofing 

 is the tendency to buckle with changing temperatures. 

 This may be materially reduced if the roofing is unrolled 

 on a level stretch, thoroughly wet, rerolled tightly, and 

 allowed to stand for several days before being placed upon 

 the roof. 



Tar-and-gravel roofing is made on the roof by means of 

 four to eight layers of tarred felt overlapped and laid in hot 

 tar. The surface is then given a heavy coat of tar into which 

 is sprinkled a well-graded smooth gravel of yi to -Hs inch 

 diameter. 



Finishing. Lath and plaster. Lath are % inch thick, 

 i x /2 inches wide, and 32 and 48 inches in length. Lath 

 should be spaced not more than ¥% inch apart, though % inch 

 is better, and must be nailed to each studding. Wood lath 

 is sold by the thousand and put up in bundles containing 

 50 or 100 lath. It requires about 1,500 lath to cover 100 

 square yards of surface. Plaster board is sometimes used 

 as a substitute for the lathing and the first coat of plaster. 

 The nature of the surface of the commercial plaster board is 

 supposed to be such that a perfect bond may be made with 

 the finish coat. Grounds are necessary for good work where 

 lath and plaster or plaster board and plaster are used. A 

 ground is a narrow strip of wood nailed to the studding 

 around door and window openings and at the top of the base- 



