266 ILLINOIS STATE DAIRYMEN'S ASSOCIATION 



than lime mortar should be used in laying up all stone foun- 

 dations. Furthermore, it is not deemed good practice to fill 

 a trench with stone of various sizes and pour mortar over 

 them. It is better to first put in the mortar and then bury as 

 many stones as possible in it. 



The practice of digging a trench and filling with concrete 

 is not recommended, unless the soil is firm and of such a nature 

 that it can be finished up smoothly. A tar or building paper 

 lining may be used to line the trenches in porous soils. It is 

 difficult to plaster concrete which has come in contact with the 

 soil. In extending a part of the silo below the surface, the 

 soil should not be used as a part of the inner form. The con- 

 crete to be durable and economical should contain only clean 

 and durable stone, gravel and sand. Brick foundations should 

 only be of hard-burned brick laid in cement mortar and when 

 so built are considered satisfactory. 



The foundation should have such an effective bearing sur- 

 face as to prevent any appreciable settling. By effective bear- 

 ing surface or area of footing is meant the area of that part 

 of the wall and floor which in case of excessive pressure helps 

 to carry the load placed on it. Fortunately, the weight of the 

 silage is supported almost entirely by the floor and not by the 

 foundation. The weight on the foundation is practically only 

 that of the wall and roof. For a concrete silo under 50 feet 

 in height, the width of footing need not be over two to four 

 times as wide as the thickness of the wall for any kind of 

 soil except soft clay or quicksand. 



The width of the foundation wall should usually be some- 

 what greater than that of the side walls on account of the ac- 

 tion of the frost. For lighter types of silos a 6 or 8-inch foun- 

 dation wall with a 12-inch footing will be sufficient except for 

 the two kinds of soil mentioned above. Many foundation walls 

 for silos fail due to uneven settling. When wire or scrap iron 

 of any considerable length may be had at little cost, it may 

 be profitably placed in the footings to prevent the formation 

 of cracks. 



