26 



VEGETABLE FORCING 



Truss construction. In recent years the truss form of 

 building (Fig. 11) has received considerable attention 

 from greenhouse men. The trussed construction makes 

 it possible to dispense with interior posts, except in very 

 wide houses, and comparatively small pipe rafters are 

 used instead of heavy, flat, iron rafters that are necessary 

 in full iron-frame houses. The sash bars are also smaller 

 than in other forms of houses, so that every detail of con- 

 struction is favorable to admitting the maximum amount 

 of light and sunshine. Theoretically, this is the ideal 



Fig. 11. A house of truss construction. 



house, and it is highly esteemed by many vegetable 

 forcers. On the other hand, some trussed houses have 

 been demolished by snow and storm, and growers are 

 naturally rather reluctant about building houses of this 

 type. It should be said, however, that improvements 

 have been made which add to the strength of the trussed 

 houses, and it is possible that the newer houses will prove 

 entirely satisfactory. Certainly no type of construction 

 could provide better conditions for the culture of winter 

 vegetables. 



Walls. The greenhouse walls should be durable and 



