When installing concrete masonry units (CMU), what is the standard height of each course including the mortar joint?
Correct Answer
B) 8 inches
Standard CMU blocks are 7⅝ inches high, and with a ⅜-inch mortar joint, each course measures exactly 8 inches. This standardized dimension allows for easy calculation and coordination with other building components.
Why This Is the Correct Answer
The standard CMU course height of 8 inches is achieved by combining the actual block height of 7⅝ inches with a standard ⅜-inch mortar joint. This creates a modular dimension that coordinates perfectly with standard door and window heights, ceiling heights, and other building components. The 8-inch module is fundamental to masonry construction planning and allows contractors to easily calculate the number of courses needed for any given wall height.
Why the Other Options Are Wrong
Option A: 6 inches
6 inches is too small for a standard CMU course and would not accommodate the actual block dimensions plus mortar joint thickness.
Option C: 10 inches
10 inches would be too large and does not correspond to any standard CMU block size plus mortar joint combination.
Option D: 12 inches
12 inches is too large and would require either oversized blocks or excessively thick mortar joints, neither of which are standard practice.
Memory Technique
Remember 'Lucky 8s' - CMU courses are 8 inches high, and 8-foot walls need exactly 12 courses (8 × 12 = 96 inches = 8 feet)
Reference Hint
Florida Building Code Chapter 21 - Masonry, or ACI 530 Building Code Requirements for Masonry Structures
More Project Mgmt Questions
What is the minimum R-value required for wall insulation in Florida Climate Zone 2?
A subcontractor brings a new chemical product to your jobsite. Under the Globally Harmonized System (GHS), what information must be immediately available to workers?
A construction site has a trench that is 8 feet deep in Type B soil. What is the maximum allowable slope ratio for the trench walls without protective systems?
A detail drawing shows a scale of 3/4" = 1'-0". If a dimension measures 2.25 inches on the drawing, what is the actual dimension?
What is the maximum recommended spacing between drywall screws when attaching to wood studs?