Masonry Magazine October 1996 Page. 13
Level line
+ ½" in 10 ft.
+%" in 20 ft.
+ ½" maximum
Elevation View
Straight line
+ ½" in 10 ft.
+" in 20 ft.
+ ½" maximum
Plan View
Another approach is somewhat more objective. Typically, an Owner or Architect will stand next to a completed masonry wall and criticize the workmanship. The quality of the workmanship may be far better than average, but the owner has a habit of visiting the jobsite while the work is still on progress at high noon on a sunny day. Even the best work will cast shadows that may never be seen upon completion of the project.
The 20 foot rule
For concrete block masonry, ASTM C 90, Section 7.3 requires visual inspection at a minimum distance of 20 feet, under conditions of diffused (indirect) lighting. The sun at high noon is not diffused lighting. Even though ASTM C 90 is a Standard Specification for Load Bearing Concrete Masonry Units, it can be strongly implied that the visual acceptance criteria also applies to the work as installed, or the complete system.
Similarly, ASTM C 216 contains visual inspection criteria for clay face brick. Type FBX is to be viewed for acceptance at a minimum distance of 15 feet, and Type FBS is to be viewed at a minimum distance of 20 feet.
Reinforcement installation.
3.4 There is an entire section dedicated to the installation of reinforcement as it applies to reinforced masonry. The structural integrity of reinforced masonry relies on the position of the reinforcement and the encasement of the grout around the steel.
The particular design will dictate he effective position of reinforcement in the system. For a basement retaining wall, vertical reinforcement would be effectively placed away from the retaining side of the wall, whereas, vertical reinforcement would be positioned near the earth side of a cantilever retaining wall.
Reinforcing-
Cantilever retaining wall
Reinforcing-
Tension
face
Compression
face
Basement retaining wall
Load
The vertical reinforcement in structural building walls is commonly in the center which effectively resists wind or seismic forces approaching from either direction. The vertical reinforcement must be within 1/2" of the detailed position relative to the face of the wall for walls not exceeding 16 inches in width. The position of the vertical reinforcement relative to the length of the wall must be within 2 inches of the location indicated on the Project Drawings.
+½" Tolerances
Specified spacing ± 2"
Vertical reinforcement tolerances
In addition to the location of the reinforcement, the grout cover must be adequate. The Code contains a simple prescriptive requirement for grout surrounding steel. For fine (sand) grout, there must be 1/4 inch clearance between the vertical or horizontal steel and adjacent materials. The clearance requirement increases to 1/2 inch when coarse (pea gravel) grout is used. The clearances are not required for spliced bars or intersecting horizontal and vertical reinforcement.
Reinforcement requirements can also be satisfied using joint reinforcement. The Code requires a minimum coverage of 1/2 inch mortar for masonry surfaces not exposed to weather and 5/8 inch mortar cover for masonry surfaces exposed to weather or soil.
" Min.
Exterior
Coverage of joint reinforcement
Continued on page 28
MASONRY-SEPTEMBER/OCTOBER, 1996 13