256 GREENHOUSES 



concrete. Experience shows that as a rule 

 they are less durable than solid walls, but 

 when the cost of material and labor for mak- 

 ing forms is considered they may be more 

 economical. They are often made with an 

 ornamental face resembling broken stone, 

 and make a somewhat more pleasing appear- 

 ance than a plain wall. 



Cost of Concrete. So many factors enter 

 into the cost of concrete that no reliable 

 general estimate can be given. The price of 

 cement is now fairly constant and uniform. 

 The cost of sand and gravel or crushed stone, 

 on the other hand, differs widely. In some 

 places it may be had on the premises, in 

 others it may have to be transported for 

 several miles. Other factors entering into 

 the cost are labor and the size of the opera- 

 tion. Where the quantity of work will justi- 

 fy the use of a powe'r mixing machine, the 

 cost is usually less than when the mixing is 

 done by expensive hand labor, although the 

 cost for labor may often be greatly reduced 

 by carefully planning the work. 



In general the contract prices for walls on 

 comparatively small jobs range from 7 to 20 

 cents per cubic foot, and for walks and floors 

 from 4 to 15 cents per square foot. 



