PRESSURES 279 



Allowable Pressures. The following unit pressures have been 

 proposed by Mr. C. C. Schneider in " Structural Design of Buildings." * 



1. Foundations. Pressure on foundations not to exceed, in tons 

 per square foot : 



Soft clay I 



Ordinary clay and dry sand mixed with clay 2 



Dry sand and dry clay 3 



Hard clay and firm, coarse sand 4 



Firm, coarse sand and gravel 6 



2. Masonry. Working pressure in masonry not to exceed, in 

 tons per square foot : 



Common brick, Rosendale-cement mortar 10 



Portland-cement mortar 12 



Hard-burned brick, Portland-cement mortar 15 



Rubble masonry, Rosendale-cement mortar 8 



Portland-cement mortar 10 



Coursed rubble, Portland-cement mortar 12 



First-class masonry, sandstone 20 



limestone 25 



granite 30 



Concrete for walls: 



Portland cement 1-2-5 2O 



" 1-2-4 25 



3. Pressure on Wall-Plates. The pressure of beams, girders, 

 wall plates, column bases, etc., on masonry shall not exceed the fol- 

 lowing, in pounds per square inch. 



On brickwork with cement mortar 200 



" rubble masonry with cement mortar 200 



" Portland-cement concrete 350 



" first-class sandstone .400 



" limestone 500 



" " " granite 600 



4. Bearing Power of Piles. The maximum load carried by any 

 pile shall not exceed 40,000 Ibs., or 600 Ibs. per sq. in. of its average 



cross-sections. 



* Trans. Am. Soc. C. E., Vol. 54, 1905. 



