InterNACHI Structural Systems Evaluation 4 — Questions and Answers
Question 1: During an inspection, the inspector finds that a steel I-beam in the basement has significant rust scaling and section loss. The MOST important evaluation is:
- The color and texture of the rust, which indicates the type of steel used
- Whether the section loss has reduced the beam's load-carrying capacity (Correct answer)
- Whether the rust has stained the concrete floor below the beam
- The age of the beam based on the rust pattern
Correct answer: Whether the section loss has reduced the beam's load-carrying capacity
Rust scaling that causes section loss directly reduces the structural capacity of the steel beam and requires engineer evaluation to determine if replacement or reinforcement is needed.
Question 2: What is the purpose of a ledger board when attached to a house for a deck?
- To provide a decorative trim piece between the deck and house siding
- To transfer deck loads to the house's structural framing (Correct answer)
- To seal the junction between the deck and house against water infiltration
- To provide lateral bracing for the deck posts
Correct answer: To transfer deck loads to the house's structural framing
A ledger board is structural — it transfers vertical loads from the deck joists to the house's band joist or rim joist and must be properly bolted, not just nailed.
Question 3: An inspector observes that a wood sill plate is soft and crumbles when probed with a screwdriver. What is the most likely cause and structural implication?
- The wood species is naturally soft and unsuitable for sill plates
- Wood decay from moisture has compromised the structural connection between foundation and framing (Correct answer)
- The lumber was improperly kiln-dried before installation
- Normal aging of older-growth lumber over several decades
Correct answer: Wood decay from moisture has compromised the structural connection between foundation and framing
A soft, crumbling sill plate indicates wood decay, which destroys the critical structural link that transfers all wall and roof loads to the foundation.
Question 4: Which method of foundation crack repair is considered MOST effective for stopping active water infiltration through a poured concrete wall?
- Painting the interior surface with waterproof masonry paint
- Hydraulic cement injection or polyurethane foam injection into the crack (Correct answer)
- Installing a drain tile system on the interior perimeter
- Applying elastomeric coating to the exterior of the foundation
Correct answer: Hydraulic cement injection or polyurethane foam injection into the crack
Polyurethane or epoxy injection into cracks seals them from within, addressing the actual infiltration pathway rather than just managing water after it enters.
Question 5: When evaluating a crawl space, an inspector finds that the wood girder is supported by a masonry pier that is leaning noticeably. What is the primary concern?
- The leaning pier may not meet local aesthetic codes
- The eccentric loading on the leaning pier could cause sudden buckling or collapse (Correct answer)
- The pier may have inadequate clearance from the crawl space vent
- The leaning indicates the pier was constructed with improper mortar
Correct answer: The eccentric loading on the leaning pier could cause sudden buckling or collapse
A leaning masonry pier subjects itself to eccentric compressive loads that can cause sudden buckling failure, making it a significant structural safety concern.
Question 6: An InterNACHI home inspector notices that the roof sheathing panels have visible gaps between them with no H-clips installed. What is the structural significance?
- The gaps will allow attic ventilation, which is actually beneficial
- Without edge support, unsupported sheathing edges can deflect under load causing waves in the roof surface (Correct answer)
- The gaps indicate the sheathing is the wrong thickness for the rafter spacing
- Missing H-clips only affect the fire rating of the roof assembly
Correct answer: Without edge support, unsupported sheathing edges can deflect under load causing waves in the roof surface
H-clips provide edge support between rafters preventing unsupported sheathing edges from deflecting under load, which can cause visible waviness and eventual panel failure.
Question 7: A home inspector observes that a cantilevered floor joist extending to support a bay window has developed a pronounced downward sag at its tip. This most likely indicates:
- The bay window glass is too heavy for the framing design
- The cantilever length exceeds safe limits or the back-span anchorage is insufficient (Correct answer)
- Normal long-term creep of wood under sustained load is within acceptable limits
- The exterior cladding on the bay window is pulling the structure downward
Correct answer: The cantilever length exceeds safe limits or the back-span anchorage is insufficient
Excessive cantilever length without adequate back-span anchorage allows the cantilevered joists to tip downward, often indicating a design or construction deficiency.
InterNACHI Structural Systems Evaluation 4
During an inspection, the inspector finds that a steel I-beam in the basement has significant rust scaling and section loss.
The MOST important evaluation is: