CRC Quality Control & Inspection 3 — Questions and Answers
Question 1: A contractor is performing a quality control review of electrical rough-in. Which of the following is a common deficiency that should be flagged?
- Romex cables stapled within 12 inches of a box
- Cables passing through bored holes without protection within 1.25 inches of the stud edge (Correct answer)
- Junction boxes secured to framing members
- Wire nuts used to splice conductors in a box
Correct answer: Cables passing through bored holes without protection within 1.25 inches of the stud edge
NEC 300.4 requires a nail plate to protect cables when the edge of a bored hole is within 1-1/4 inches of the face of the framing member.
Question 2: What is the purpose of a mock-up panel in residential construction quality control?
- To estimate material quantities for the project
- To establish an approved standard of workmanship that field work must match (Correct answer)
- To test the structural capacity of wall assemblies
- To document subcontractor qualifications
Correct answer: To establish an approved standard of workmanship that field work must match
A mock-up establishes an agreed-upon benchmark of acceptable quality for finishes, materials, or assemblies before full-scale installation begins.
Question 3: During a quality inspection of a roof truss installation, the inspector notices several trusses have been field-cut to fit around a chimney chase. This is:
- Acceptable if the cuts are clean and straight
- Acceptable if metal straps are added across the cut
- A serious deficiency requiring engineer approval before proceeding (Correct answer)
- Standard practice that requires only a supervisor's sign-off
Correct answer: A serious deficiency requiring engineer approval before proceeding
Trusses are engineered components; field modifications must be evaluated and approved by the truss engineer of record before the structure can be considered safe.
Question 4: Which ASTM standard governs the minimum compressive strength testing of concrete cylinders used to verify residential foundation concrete quality?
- ASTM C39 (Correct answer)
- ASTM C150
- ASTM C567
- ASTM C94
Correct answer: ASTM C39
ASTM C39 is the standard test method for compressive strength of cylindrical concrete specimens and is the primary QC test for verifying design strength.
Question 5: A residential contractor's QC program should require that drywall screws used for 1/2-inch drywall on wood framing be driven to what depth standard?
- Flush with the surface
- Slightly dimpled without breaking the paper face (Correct answer)
- Countersunk 1/4 inch below the surface
- Driven until resistance is felt regardless of paper condition
Correct answer: Slightly dimpled without breaking the paper face
Proper drywall screw installation creates a slight dimple without tearing the paper face; breaking the paper reduces holding power and creates a finishing defect.
Question 6: When conducting a pre-drywall inspection, which structural element is most critical to verify before walls are closed in?
- Paint color selection
- Proper installation of blocking for future grab bars and fixtures (Correct answer)
- Cabinet door hinge type
- Flooring subgrade preparation
Correct answer: Proper installation of blocking for future grab bars and fixtures
Blocking for future grab bars, handrails, and heavy fixtures must be installed before drywall since retrofitting requires destructive work later.
Question 7: A quality audit reveals that a subcontractor has been using Type N mortar instead of specified Type S mortar for below-grade masonry. The primary concern is:
- Type N mortar costs more than Type S
- Type N has lower compressive strength and inadequate durability for below-grade use (Correct answer)
- Type N mortar is not available in the required color
- Type N sets faster, causing scheduling delays
Correct answer: Type N has lower compressive strength and inadequate durability for below-grade use
Type S mortar has higher compressive strength and greater resistance to freeze-thaw and soil sulfate exposure than Type N, making it mandatory for below-grade applications.
CRC Quality Control & Inspection 3
A contractor is performing a quality control review of electrical rough-in.
Which of the following is a common deficiency that should be flagged?