InterNACHI Structural Systems Evaluation 3 — Questions and Answers
Question 1: An inspector observes that roof rafters are pulling away from the ridge board at their connection points. The MOST likely cause is:
- The ridge board is installed at too steep an angle
- Outward thrust from inadequate rafter ties combined with heavy roofing material (Correct answer)
- The rafters are made from green (unseasoned) lumber that has dried and shrunk
- Termite damage has weakened the rafter tails
Correct answer: Outward thrust from inadequate rafter ties combined with heavy roofing material
Heavy roofing materials increase the outward thrust at rafter bases, and without adequate ties this force can cause rafters to separate from the ridge board.
Question 2: According to InterNACHI standards, when an inspector observes conditions that appear to exceed their scope of knowledge, they should:
- Note the condition as acceptable and move on
- Recommend evaluation by a qualified structural engineer (Correct answer)
- Refuse to complete the inspection until the issue is resolved
- Apply their best judgment and provide a repair estimate
Correct answer: Recommend evaluation by a qualified structural engineer
InterNACHI standards require inspectors to recommend specialist evaluation when conditions are beyond their expertise rather than making unfounded determinations.
Question 3: An inspector finds that the floor of a home has a noticeable slope toward the center of the house. Which structural condition would MOST likely cause this?
- The flooring material has warped due to moisture
- The central support beam or posts have settled or failed (Correct answer)
- The floor joists were installed with the crown facing downward
- Normal wood shrinkage has occurred over time
Correct answer: The central support beam or posts have settled or failed
A floor that slopes toward the center suggests settlement or failure of the central girder or its supporting posts, causing the floor system to sag at that point.
Question 4: Which of the following is a sign of active structural movement in a foundation wall as opposed to old, stabilized cracking?
- Cracks with staining or efflorescence on the edges
- Cracks with fresh, light-colored edges and no staining (Correct answer)
- Cracks that have been previously patched
- Cracks that are hairline width throughout their length
Correct answer: Cracks with fresh, light-colored edges and no staining
Fresh, clean crack edges without staining or debris accumulation indicate recent movement, while stained, weathered crack edges suggest old, potentially stable cracks.
Question 5: A home inspector notices that the floor joists in a basement span 18 feet without intermediate support. The joists appear undersized for this span. What is the primary visible symptom likely to be observed?
- Twisting and rotation of the joists along their length
- Excessive deflection (bounce or sag) in the floor above (Correct answer)
- Horizontal splitting along the grain at joist ends
- Vertical cracking in the walls adjacent to the floor
Correct answer: Excessive deflection (bounce or sag) in the floor above
Undersized joists spanning excessive distances will deflect (sag) under load, which manifests as a bouncy or sloping floor above.
Question 6: When inspecting a wood-framed wall, an inspector notes that the wall studs are 24 inches on center rather than the typical 16 inches. What structural concern should be noted?
- Fire blocking requirements are not met at 24-inch spacing
- The wall may have reduced lateral load and shear resistance (Correct answer)
- Electrical wiring cannot be properly supported at 24-inch spacing
- Insulation cannot be installed between 24-inch spaced studs
Correct answer: The wall may have reduced lateral load and shear resistance
Wider stud spacing reduces the wall's ability to resist lateral (wind and seismic) loads and may require engineering review depending on the application.
Question 7: An inspector observes diagonal cracks radiating from the corners of window and door openings in a concrete block wall. This pattern suggests:
- Improper installation of window flashing
- Settlement or movement causing stress concentrations at opening corners (Correct answer)
- Thermal expansion cracking due to sun exposure
- Water infiltration deteriorating the mortar
Correct answer: Settlement or movement causing stress concentrations at opening corners
Diagonal cracks radiating from corners of openings are classic indicators of differential settlement or structural movement creating stress concentrations at those points.
InterNACHI Structural Systems Evaluation 3
An inspector observes that roof rafters are pulling away from the ridge board at their connection points.
The MOST likely cause is: