52 FARM BUILDINGS IN SOUTH AFRICA 



the roof-covering should be either built in cement mortar, or plastered 

 with cement mortar, to enable it to resist the weather. 



The bond will be much broken, but general principles should be kept 

 in view while the chimney is being built. 



Rendering. — Sometimes, but rarely in South Africa, the inside of flues 

 is rendered with 1 to 3 cement mortar. 



Pargetting or Parging. — The more common procedure, in this country, 

 is to plaster the inside of the flues with 1 part lime to 3 parts cow-dung, 

 or with 1 part good clay to 3 parts cow-dung. This forms a lining 

 which is smooth, tough, and not easily cracked. 



Coring, etc. — As a flue, in process of being built, rises, it should be 

 kept plugged a little below building-level by a bundle of rags or shavings 

 called a " sweep." This prevents mortar from falling down, and adhering 

 to the sides of, the flue. 



After a flue is finished it is advisable to pass a wire- brush, or " core," 

 through it to clear away any small obstructions. 



Round Flues. — A round flue is theoretically the most perfect, but is 

 difficult to build. Earthenware pipes, jointed with 1 to 2 cement mortar 

 and surrounded by brickwork, are sometimes used. 



