304 ENGINEERING ON THE FARM 



Weight of Soils per Cubic Yard 



Loam 2,100-2,400 pounds 



Clay 2,400-2,800 pounds 



Sand 2,500-3,000 pounds 



Gravel 2,600-3,300 pounds 



THE BASE 



Foundations. The foundation is that portion of a 

 structure which serves as a base upon which to erect the 

 superstructure. It may be all or in part below the ground. 

 The object of any foundation is to form such a solid base 

 that no movement shall take place after the superstructure 

 is erected. Nearly all structures will settle to some extent 

 unless built on solid rock, as soils become compressed 

 under the weight of heavy buildings. Care should be taken 

 that a foundation is evenly loaded and properly propor- 

 tioned in order that settling may be uniform and cracks 

 thereby avoided. A 12-inch wall is considered the thinnest 

 that can be built in any but very short lengths and small 

 depths. Where city ordinances cover this point, a 12-inch 

 wall is the minimum, although an 8-inch concrete wall 

 would be amply strong for most residences. Rubble stone 

 wall is generally 16 to 20 inches thick. A concrete wall is 

 usually the most satisfactory, because it can be made the 

 minimum thickness and placed by unskilled labor. Brick 

 is satisfactory where a hard-burned quality of brick is to 

 be had. Hollow tile are amply strong if full-mortared 

 joints are used. Water will find its way through all of 

 these walls with the exception of the monolithic concrete. 



Number of Tons Which a Square Foot of Different 

 Soils in Their Natural State Will Support 



