82 GREENHOUSES 



and (3) all-iron or all-steel frame. In wood 

 and semi-iron construction, rafters are sel- 

 dom used, the sash bars performing this func- 

 tion as well as their own. These forms have 

 the advantage of being somewhat cheaper 

 than the all-metal frame construction, and 

 have the additional advantage that the ma- 

 terial may be cut and fitted on the job by any 

 experienced workman. 



Wood frame houses cast more shade than 

 semi-iron, and are less durable, especially the 

 posts. Semi-iron houses are very durable, 

 and for houses of medium width, are very 

 satisfactory. Probably more houses of this 

 type have been built during the past ten years 

 than of all others, though the all-metal frame 

 house is now gaining in favor. This is 

 especially true in the East, where large 

 houses are coming into vogue. 



The all-metal frames are cut and fitted at 

 the factory and are then shipped, knocked 

 down, to the place of erection. Most styles 

 of all-metal frames have rafters, which are 

 bolted to the side posts by means of gusset 

 plates to form bents. The bents are then 

 placed in position and secured there by stays 

 and purlins. Upon this framework are then 

 bolted the wood sash bars and glazing 



