96 



GREENHOUSES 



with greater ease than any semi-iron house 

 they had ever built. 



Fig. 56. A method of 

 erecting small all-metal 

 frame houses 



Structural steel is most largely used in 

 truss-frame houses though gaspipe is now 

 quite popular. It is claimed for gaspipe that 

 it costs less than structural steel and that it 

 casts less shade. Some objection has been 

 urged against houses constructed of gaspipe 

 on account of a lack of rigidity, but as now 

 constructed they give very satisfactory serv- 

 ice. Houses of this type are regularly sup- 

 plied by manufacturers up to 54 feet in width, 

 without center supporting posts. It is prob- 

 ably safest to have two rows of supporting 

 posts in houses more than 40 feet in width. 



