270 BRIDGE ABUTMENTS AND PIERS. CHAP. VI. 



i 



23. Face or Surface. Exposed surfaces of the face stone shall be rock-faced, and edges pitched 

 to the true lines and exact batter; the face shall not project more than three (3) in. beyond the 

 pitch line. 



24. Chisel drafts one and one-half (i) in. wide shall be cut at exterior corners. 



25. Holes for stone hooks shall not be permitted to show in exposed surfaces. Stone shall 

 be handled with clamps, keys, lewis or dowels. 



26. Stretchers. Stretchers shall not be less than four (4) ft. long and have at least one and a 

 quarter times as much bed as thickness of course. 



27. Headers. Headers shall not be less than four (4) ft. long, shall occupy one-fifth of face 

 of wall, shall not be less than eighteen (18) in. wide in face, and, where the course is more than 

 eighteen (18) in. high, width of face shall not be less than height of course. 



28. Headers shall hold in heart of wall the same size shown in face, so arranged that a header 

 in a superior course shall not be laid over a joint, and a joint shall not occur over a header; the 

 same disposition shall occur in back of wall. 



29. Headers in face and back of wall shall interlock when thickness of wall will admit. 



30. Where the wall is three (3) ft. thick or less, the face stone shall pass entirely through. 

 Backing shall not be permitted. 



*3i-a. Backing. Backing shall be large, well-shaped stone, roughly bedded and jointed; 

 bed joints shall not exceed one (i) in. At least one-half of the backing stone shall be of same 

 size and character as the face stone and with parallel ends. The vertical joints in back of wall 

 shall not exceed two (2) in. The interior vertical joints shall not exceed six (6) in. Voids shall 



be thoroughly filled with y Mded {n cement mor ^ 



T concrete. 

 3i-b. Backing shall be j headers and stretchers, as specified in paragraphs 26 and 27, and 



( heart of wall filled with concrete. 



32; Where the wall will not admit of such arrangement, stone not less than four (4) ft. long 

 shall be placed transversely in heart of wall to bond the opposite sides. 



33. Where stone is backed with two courses, neither course shall be less than eight (8) in. 

 thick. 



34. Bond. Bond of stone in face, back and heart of wall shall not be less than twelve (12) 

 in. Backing shall be laid to break joints with the face stone and with one another. 



35. Coping. Coping stone shall be full size throughout, of dimensions indicated on the 

 drawings. 



36. Beds, joints and top shall be fine-pointed. 



37. Location of joints shall be determined by the position of the bed plates, and be indicated 

 on the drawings. 



38. Locks. Where required, coping stone, stone in the wings of abutments, and stone 

 on piers, shall be secured together with iron clamps or dowels, to the position indicated on the 

 drawings. 



BRIDGE AND RETAINING WALL MASONRY RUBBLE STONE. 



39. Dressing. The stone shall be roughly squared, and laid in irregular courses. Beds shall 

 be parallel, roughly dressed, and the stone laid horizontal to the wall. Face joints shall not be 

 more than one (i) in. thick. Bottom stone shall be large, selected flat stone. 



40. Laying. The wall shall be compactly laid, having at least one-fifth the surface of back 

 and face headers arranged to interlock, having all voids in the heart of the wall thoroughly filled 



with I con . crete - 



' \ suitable stones and spalls, fully bedded in cement mortar. 



ARCH MASONRY ASHLAR STONE. 



41. Arch Masonry, Ashlar Stone. Voussoirs shall be full size throughout and dressed true 

 to templet, and shall have bond not less than thickness of stone. 



42. Dressing. Joints of voussoirs and intrados shall be fine-pointed. Mortar joints shall 

 not exceed three-eighths (f) in. 



f smooth. 



43. Face or Surface. Exposed surface of the ring stone shall be \ rock faced, with a marginal 



( draft. 



44. Number of courses and depth of voussoirs shall be indicated on the drawings. 



45. Voussoirs shall be placed in the order indicated on the drawings. 



* Paragraphs 3i-a and 3i-b are so arranged that either may be eliminated according to 

 requirements. Optional clauses printed in italics. 



