24 



VEGETABLE FORCING 



Semi-iron construction (Fig. 10) is becoming popular in 

 all parts of the country. It provides for concrete walls, 

 iron posts embedded in concrete, iron purlins and purlin 

 supports, iron braces and sometimes iron eaves-plates. 

 The iron may be in the form of pipe, angle irons, or 

 simply flat bars, the form depending upon their function 

 and the cost and preference of the builder. With the best 

 forms of semi-iron construction, decayed wood parts are 

 easily removed and replaced with new parts. When all 

 exposed parts of wood and iron are kept properly painted, 

 the house, with only slight repairs, should last 25 years, 

 and then the renewal of decayed sash bars or other parts 



Fig. 9. A modern steel-frame house. Note large door. 



should prepare it for many more years of service. The 

 moderate cost and serviceability of semi-iron construc- 

 tion appeal to commercial growers. 



Iron construction (Fig. 9) is the strongest and most 

 durable. In addition to the iron parts used for semi-iron 

 construction, the gutters, wall and side plates are metal, 

 and there are a certain number of iron rafters to support 

 the roof, so that interior posts are unnecessary. Iron con- 

 struction gives the house greater rigidity, and there is 

 less shading of the plants because of the absence of in- 

 terior posts. Full iron construction costs considerably 

 more than semi-iron, and this is the only reason why it 

 is not more generally employed. 



