InterNACHI Deck Inspector flashcards

31 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ledger board

The horizontal board fastened to the house's band joist or rim that supports the inner ends of the deck joists. It is a primary load path and a common location of water damage and fastener defects.

Ledger flashing

Metal or membrane that sheds water over the top of the ledger and behind the siding. Missing or reversed flashing traps water against the rim joist and causes hidden decay.

Lag screw withdrawal

A failure mode where fasteners pull out of the band joist under tension. It occurs when a ledger is fastened only with nails, undersized screws, or screws placed too close to the board edge.

Joist hanger nails

Hangers require the manufacturer-specified structural nails or screws, fully driven. Deck screws, roofing nails, or partially driven fasteners reduce capacity and are reportable defects.

Beam bearing on post

The beam should rest on top of the post or in an approved notch or cap. A beam bolted to the post's side without bearing relies on fasteners in withdrawal and is typically a defect.

Post footing

A concrete support extending below frost depth that carries the deck post. Posts set on soil, thin blocks, or untreated wood in contact with ground are common defects.

Guard height requirement

Guards are needed at open sides more than 30 inches above grade. Minimum height is usually 36 inches, with 42 inches required in some jurisdictions and for commercial occupancies.

Four-inch sphere rule

A 4-inch sphere must not pass through any guard opening, including the triangle formed by a stair tread, riser, and bottom rail, to prevent a child from passing through or becoming entrapped.

Graspable handrail

A handrail profile that a hand can grip, typically 1.5 to 2 inches in cross-section, with about 1.5 inches of clearance from the wall. Required on stairs with four or more risers in many codes.

Stair riser uniformity

Riser heights and tread depths should be consistent across the flight, commonly within about 3/8 inch. Variations create trip hazards and are a frequent defect on site-built deck stairs.

Deck board spacing

Gaps between deck boards allow drainage and reduce cupping. Gaps too tight trap water and promote rot; gaps too wide create trip and heel hazards, especially on stair treads.

Treated lumber corrosion

Preservative-treated wood, especially newer copper-based treatments, accelerates corrosion of standard galvanized fasteners. Connectors should be rated for the exposure, such as hot-dip galvanized or stainless steel.

Decay probing

Pressing a tool into suspect wood at post bases, ledger ends, joist ends, and stringers reveals soft or hollow wood. Probing is a non-invasive way to identify concealed rot during a visual inspection.

Joist cantilever limits

Joists may overhang a beam only within the design limits, commonly about one-quarter of the span. Excessive cantilevers cause deflection and are a structural concern to report.

Diagonal deck bracing

Decks elevated on posts may need diagonal bracing or a braced frame to resist lateral movement. Wobble or visible racking when walked on is a reportable condition.

Stair stringer support

Stringers must be supported at the top and bottom and sized for the span. Stringers nailed to the deck rim without a bearing connection or hanger are a common defect.

InterNACHI SOP scope

The Standards of Practice define a visual, non-invasive inspection of readily accessible components. Structural calculations, soil bearing capacity, and concealed conditions are excluded and should be disclaimed in the report.

Unsafe deck access

If a deck appears unsafe, the inspector is not required to walk on it. The report must state the limitation and reason, and the condition should be described as a material safety defect.

Material defect

A condition that significantly affects value, safety, or use of the property. Missing ledger fasteners, guard openings over 4 inches, and unsupported stringers are examples reported as material.

Safety hazard reporting

Safety hazards are reported as such regardless of the deck's age. Guard openings, missing handrails, and ledger fastening defects fall in this category rather than under maintenance.

Deferred maintenance

Items that are worn or cosmetic but not currently unsafe, such as weathered boards or loose decking screws. These are identified as maintenance recommendations, distinct from structural or safety defects.

Recommendation wording

Each significant finding should carry a recommendation naming the appropriate professional, such as a licensed deck contractor, structural engineer, or electrician, so the client knows the next step.

Code citation disclaimer

The inspector is a generalist and does not certify code compliance. Code references in a report are informational and vary by jurisdiction; the report describes observed conditions against the SOP.

Report component description

The report should identify the deck and describe visible materials and components, including framing, decking, guards, stairs, and posts, before listing defects and recommendations.

Labeled photographs

Photos should be labeled with location and orientation so the client can find the defect. The written narrative must still describe the finding; a photo alone is insufficient.

Excluded items list

Items outside the deck inspection, such as hot tubs, detached stairs, or roofs accessed from the deck, should be explicitly listed as excluded or separately inspected in the report.

Verbal versus written

Findings stated during the walkthrough do not replace the written report. Material safety defects should be communicated promptly and documented with the same wording used in the report.

Limitation statement

A required statement describing what was not inspected and why, such as snow cover, stored items, or refused access. It protects both client and inspector and must accompany the findings.

Client agreement

The signed contract defines the scope, fees, and limitations before the inspection. Deck-specific exclusions should appear in both the agreement and the final report for consistency.

Electrical on decks

Receptacles, lighting, and hot tub circuits on a deck are electrical components. The inspector observes them for obvious defects and recommends an electrician for further evaluation rather than testing them.

Structural engineer referral

Referral is appropriate when the inspector observes movement, excessive deflection, or an unconventional connection that cannot be evaluated visually. The engineer performs the load and connection analysis outside the SOP.