FRAMEWORK 91 



a quarter-inch pipe and should be supported 

 by posts every 8 feet. Purlin posts are usual- 

 ly of one and a half-inch pipe and braces of 

 one and a quarter-inch pipe. 



A well-built house of this type, if well 

 cared for, should last a lifetime. 



Fig. 52. Section of truss-frame greenhouse. The frame 

 is made of gaspipe 



Semi-iron frames are also made from struc- 

 tural iron instead of pipe. They are just as 

 satisfactory, but are not so easily worked, 

 and are usually cut and fitted at the factory. 



All-metal Frame Houses. There are three 

 types of all-metal framework: (i) Those in 

 which the roof is supported by interior posts, 

 much the same as in the wood or semi-iron 

 houses. (2) Those in which the roof is sup- 



