FOUNDATIONS 



313 



different foundation soils shall not exceed the values given 

 in the accompanying table 



The observance of the revised building laws of the several 

 cities is considered good engineering practice, for they are 

 usually the results of careful investigations and records of 

 long experience. The following, taken from the New York 

 Building Laws, is interesting and gives bearing values that 

 are well within the safe limits: 



SAFE BEARING VALUES OF DIFFERENT FOUNDATION 

 SOILS 



Material 



Tons per 



Square 



Foot 



Granite rock formation 



Limestone, compact beds 



Sandstone, compact beds 



Shale formation, or soft friable rock 



Gravel and sand, compact 



Gravel, dry and coarse, packed and confined 



Gravel and sand, mixed with dry clay 



Clay, absolutely dry and in thick beds 



Clay, moderately dry and in thick beds 



Clay, soft (similar to Chicago clay) ............ 



Sand, compact, well -cemented, and confined . . . 

 Sand, clean and dry, in natural beds and confined 

 Earth, solid, dry, and in natural beds .......... 



30 

 25 



20 



8 to 10 

 6 to 10 



6 

 4 to 6 



4 



3 

 1 to 1 



4 



2 



4 



Where no test of the sustaining power of the soil is made, 

 different soils, excluding mud, at the bottom of the footings 

 shall be deemed to sustain safely the following loads to the 

 superficial foot: 



Soft clay, 1 T. per sq. ft. 



Ordinary clay and sand together, in layers, wet and 

 springy, 2 T. per sq. ft. 



Loam clay, or fine sand, firm and dry, 3 T. per sq. ft. 



Very firm, coarse sand, stiff gravel, or hard clay, 4 T. per 

 sq. ft., or as otherwise determined by the Commissioner of 

 Buildings having jurisdiction. 



