Walls $ I 



for this. They are placed where the ten- 

 sile stress occurs. If a load is applied 

 to a concrete beam, the tendency to bend 

 causes the molecules in the upper part of 

 the beam to be compressed and those in 

 the lower part to be pulled asunder. The 

 steel rod or rods placed below the center, 

 by their great tensile qualities, supply the 

 needed strength. Posts should have two 

 rods, placed vertically in diagonal corners 

 and walls can have either rods placed ver- 

 tically or a steel mesh running lengthwise 

 with the wall. If a wall is thick and not 

 high in proportion to its width this re- 

 enforcing is not necessary. Expansion 

 joints should be left in all continuous walls 

 and precise information about these is ob- 

 tained from the hand books. 



COST 



It is difficult to lay down definite figures 

 for the cost of building walls and fences. 

 Material and labor vary from year to year 

 and from place to place. Therefore what 

 follows should be regarded as only approx- 

 imate although every precaution has been 

 taken to be accurate. 



