InterNACHI Deck Inspector cheat sheet

Inspection sequence: ledger-to-house attachment, then joist-to-ledger and joist-to-beam connections, then post-to-footing and beam bearing, then decking, stairs, guards, and railings; structural load path is evaluated before finish and cosmetic items.

Ledger fastening: through-bolts or lag screws sized per the deck's design, with washers; common defect is a ledger attached with nails, undersized or too few fasteners, or fasteners spaced too widely along the band joist.

Ledger flashing defect: missing or improperly layered flashing lets water reach the rim/band joist; correct order is flashing over the ledger and behind the siding so water sheds outward, not trapped between ledger and house.

Joist hangers: every joist requires a hanger or approved connection at the ledger unless the design uses a structural ledger with bearing; defects include missing hangers, hangers fastened with the wrong nails (e.g., deck screws or short roofing nails), and hangers not fully seated on the joist.

Beam-to-post connection: beam must bear on the post or in an approved post cap/notch; a beam merely bolted to the side of a post relies on the fasteners in withdrawal and is a defect unless the connection is engineered.

Post footings: posts must bear on concrete footings below frost depth or on approved pier systems; defects include posts set directly on soil, on thin precast blocks, or embedded in soil without decay protection.

Guard requirements: guards are required at open sides of decks more than 30 inches above grade and at stairs with more than two risers; typical minimum height is 36 inches, with 42 inches used in some jurisdictions and for commercial occupancies.

Guard infill: a 4-inch sphere must not pass through any opening in the guard, including the triangular space between a stair tread, riser, and bottom rail; baluster spacing and decorative panel patterns are checked with this gauge.

Stair geometry: riser height and tread depth should be uniform within about 3/8 inch across the flight; handrails on stairs with four or more risers, graspable profile, and 1.5- to 2-inch clearance from the wall are commonly required.

Decking defects: board spacing too tight traps water and promotes rot; too wide creates trip and heel hazards; fasteners that back out, corroded connectors in treated lumber, and stair treads without adequate support are reportable.

Wood decay and fastener corrosion: probe post bases, ledger ends, joist ends, and stair stringers; in preservative-treated lumber, standard galvanized fasteners may corrode - connectors should be rated for the exposure (hot-dip galvanized, stainless, or manufacturer-approved coating).

Scope of a deck inspection under the InterNACHI SOP is a visual, non-invasive, readily accessible inspection; concealed conditions, soil bearing capacity, and structural engineering calculations are outside the scope and should be disclaimed in the report.

The inspector is not required to walk on a deck that appears unsafe; if access is refused or limited, the report must state the limitation and the reason, and the condition should be treated as a material defect rather than ignored.

Report format: identify the deck, describe materials and visible components, state observed defects with location, and give a recommendation (repair, evaluate by a qualified contractor or engineer, or monitor) for each significant finding.

Defect classification: safety hazards (guard openings, missing handrail, ledger fastening) are reported as such regardless of age; deferred maintenance and cosmetic items are identified as maintenance rather than structural failure.

Photographs should be labeled with location and orientation so the client can find the defect; the narrative must not rely on the photo alone to convey the finding.

The report must distinguish inspected systems from excluded ones: detached stairs, hot tubs, and roofs accessed from the deck are separate items and should be listed as inspected or excluded explicitly.

Recommendations must name the appropriate trade or professional - licensed deck contractor, structural engineer, or electrician for deck lighting and receptacles - rather than leaving the client to interpret the defect.

The inspector is a generalist and does not certify a deck as code-compliant; the report describes observed conditions against the standard of practice, and code citations, when given, are informational and jurisdiction-dependent.

Client communication: verbal findings during the walkthrough do not replace the written report; material safety defects should be communicated promptly and documented in writing with the same wording used in the report.