86 GREENHOUSES 



The next step is to place the center posts, 

 which are usually 2 x 3 or 2 x 4 inches in 

 size. The height of the ridge having 

 been determined (see Chapter III) these 

 posts are cut long enough to allow the 

 lower end to be set in the ground about 2 

 feet. They are then put in alignment and 

 embedded in concrete the same as the side 

 posts. The ridge is then put in place on top 

 of -these center posts, and the eave plate on 

 top of the side posts, all joints being set in 

 thick white lead paint. 



The sash bars on a house over 12 feet in 

 width must be supported with purlins, but it 

 is not necessary to support them with two 

 extra rows of posts. A perfectly safe and 

 much more convenient way is to support 

 them with arms or braces from the center 

 posts. This saves valuable ground space, and 

 the arms serve to stiffen the center posts as 

 well. The length and position of these arms 

 may be determined by placing a straight edge 

 from ridge to eave plate in just the position 

 the sash bars will occupy, and nailing the 

 arms fast, first allowing for the thick- 

 ness of the purlin. A good mechanic would 

 have determined this before the posts were 



