100+ Free InterNACHI Deck Inspector Practice Questions

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Which observation most strongly indicates corrosion of a metal joist hanger?

Flaking rust, perforations, white powder from sacrificial zinc, or significant section loss

Slight surface dust

A printed manufacturer label

Mill markings on the surface

to track

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2026 Statistics

Key Facts: InterNACHI Deck Inspector Exam

Final Exam Questions

InterNACHI online final

~80%

Weighted Cut-Off

InterNACHI

Exam Fee for Members

Included with InterNACHI membership

36 in

Min Guard Height

IRC R312.1.2

4 in

Max Baluster Sphere

IRC R312.1.3

1,500 lb

Lateral Hold-Down Rating

IRC R507.9.2

InterNACHI's Certified Deck Inspector exam is a 25-question online final drawn from a larger pool of multiple-choice questions. It is free for members and self-paced, with a weighted ~80 cut-off. The curriculum covers DCA-6 ledger/footing rules, IRC R507 deck construction, R311.7 stair geometry, R312 guards (36-in height, 4-in sphere, 200-lb load), and the inspection methodology for decay, corrosion, and lateral movement.

Sample InterNACHI Deck Inspector Practice Questions

Try these sample questions to test your InterNACHI Deck Inspector exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1According to AWC DCA-6, what is the minimum diameter of lag screws or bolts used to fasten a deck ledger to a band joist?

A.3/8 inch

B.1/2 inch

C.5/8 inch

D.3/4 inch

Explanation: DCA-6 specifies 1/2-inch diameter lag screws or through-bolts (with washers) for attaching a deck ledger to a 2-inch nominal band joist or 1-inch LVL rim joist. Smaller diameters are not permitted under the prescriptive guide.

2DCA-6 Table 5 specifies fastener on-center spacing based on which parameter?

A.Total deck area in square feet

B.Deck joist span

C.Number of stair risers

D.Ledger board length

Explanation: DCA-6 Table 5 sets lag screw/bolt spacing based on the deck joist span (assuming a 40 psf live and 10 psf dead load). Longer joist spans transfer more load to each ledger fastener, so spacing tightens as span increases.

3For a deck with a 14-foot joist span, DCA-6 requires 1/2-inch lag screws into a 2-inch nominal band joist to be spaced no further apart than what on-center distance?

A.9 inches o.c.

B.13 inches o.c.

C.18 inches o.c.

D.24 inches o.c.

Explanation: Per DCA-6 Table 5, 1/2-inch lag screws into a 2-inch nominal band joist must be spaced 13 inches o.c. for a 14-foot deck joist span. Larger spans demand tighter spacing because each fastener carries more tributary load.

4Which ledger attachment condition is NOT permitted by DCA-6 or IRC Section R507?

A.Ledger fastened with 1/2-inch through-bolts to a 2x band joist

B.Ledger fastened with 1/2-inch lag screws to a 2x band joist

C.Ledger fastened with lag screws to brick or stone veneer

D.Ledger fastened with lag screws to a 1-inch LVL rim joist

Explanation: IRC R507.2 prohibits supporting deck ledgers on stone or masonry veneer because veneer is not designed to transfer load to the structure. Through-bolts and lags into a structural band joist or LVL rim are both permitted by DCA-6 and the IRC.

5Per IRC R507.2.4, what is the minimum nominal thickness of corrosion-resistant metal flashing used at the deck ledger?

A.0.010 inch

B.0.019 inch

C.0.032 inch

D.0.040 inch

Explanation: IRC R507.2.4 requires corrosion-resistant metal flashing of nominal thickness not less than 0.019 inch, or an approved non-metallic flashing compatible with the substrate and decking. This is approximately 26-gauge.

6Where must deck ledger flashing be installed in relation to the wall covering?

A.Surface-applied with sealant over the siding

B.Lapped behind the wall covering and over the top of the ledger

C.Inside the wall cavity only

D.Below the ledger at the bottom edge only

Explanation: Per IRC R703.4 (referenced by R507.2.4), flashing must be lapped behind the wall covering above and turned out over the top of the ledger so water drains down and out, not behind the ledger into the band joist.

7During inspection, you observe deck ledger lag screws spaced at 28 inches on-center for a 12-ft joist span. What is the correct finding?

A.Compliant if the screws are 1/2-inch diameter

B.Compliant if the ledger is a 2x10 or larger

C.Defect — DCA-6 requires tighter spacing at this span

D.Compliant if a structural engineer signed the original drawings

Explanation: DCA-6 Table 5 requires roughly 15 inches o.c. for a 12-ft joist span; 28 inches o.c. greatly exceeds the prescriptive maximum and the ledger is significantly under-fastened. Report as a defect requiring repair by a qualified contractor.

8DCA-6 Figure 19 requires deck ledger lag screws and bolts to be installed in what pattern?

A.Aligned in a single horizontal row

B.Aligned in two parallel horizontal rows

C.Staggered along the ledger

D.Concentrated near each end of the ledger

Explanation: DCA-6 Figure 19 shows lag screws/bolts staggered (offset top to bottom) along the ledger. Staggering avoids splitting the ledger or band joist along a single grain line and distributes load.

9What is required when a deck ledger is attached to a house with a band joist of unknown framing (e.g., behind a finished basement ceiling)?

A.Assume the band joist is solid-sawn lumber

B.Proceed with standard DCA-6 spacing

C.Verify the band joist material and provide blocking if it is an open-web or unverifiable assembly

D.No verification is needed if the house is less than 20 years old

Explanation: DCA-6 and R507 only apply to specific band joist materials (2-inch solid-sawn lumber or 1-inch LVL). Where framing is hidden or non-conforming (e.g., I-joists, open-web trusses), an engineered design or alternate blocking is required. Inspectors should flag and recommend verification.

10Which fastener type is NOT permitted by DCA-6 to attach a deck ledger directly to a house band joist?

A.1/2-inch lag screws with washers

B.1/2-inch through-bolts with washers

C.Nails alone, regardless of diameter or quantity

D.Proprietary structural screws listed in an ESR/code report at equivalent capacity

Explanation: Nails are never permitted as the primary deck ledger fastener. DCA-6 explicitly requires 1/2-inch lag screws or bolts (or proprietary fasteners with a current evaluation report demonstrating equivalent capacity).

About the InterNACHI Deck Inspector Exam

The InterNACHI Certified Deck Inspector designation is awarded to inspectors who complete the InterNACHI How to Perform Deck Inspections course and pass the online final exam. The credential covers residential deck inspection: ledger attachment and flashing, footings and posts, beams and joists, decking and fastening, guards and railings, stairs and handrails, and defect identification including rot, decay, and fastener corrosion. Content is aligned with the American Wood Council DCA-6 Prescriptive Residential Wood Deck Construction Guide and IRC Section R507.

Questions

25 scored questions

Time Limit

Self-paced

Passing Score

Weighted; ~80 cut-off

Exam Fee

Free for InterNACHI members (InterNACHI (International Association of Certified Home Inspectors))

InterNACHI Deck Inspector Exam Content Outline

16%

Ledger Attachment

Lag screws/through-bolts per DCA-6 Table 5, flashing per IRC R703.4, blocking, lateral hold-down

16%

Footings & Posts

Concrete piers, helical piles, frost depth, IRC R507.3 footing sizes, PT post bearing

14%

Beams & Joists

Southern Pine #2 span tables, beam-on-post hardware, joist hangers, cantilever 1/4 backspan

16%

Decking & Fastening

PT vs composite vs PVC vs hardwood; hidden fastener clips; gap spacing; screw vs nail

16%

Guards & Railings

IRC R312 36-in height, 4-in sphere, stair 4-3/8 in & 6-in triangle, 200-lb point load

14%

Stairs

IRC R311.7 7-3/4 in riser, 10 in tread, 3/8-in variation, 34-38 in handrail, graspability

Inspection Methodology & Decay

Hammer test, rot signs, fungal/insect damage, corroded connectors, lateral movement

How to Pass the InterNACHI Deck Inspector Exam

What You Need to Know

Passing score: Weighted; ~80 cut-off
Exam length: 25 questions
Time limit: Self-paced
Exam fee: Free for InterNACHI members

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

InterNACHI Deck Inspector Study Tips from Top Performers

1Memorize DCA-6 ledger fastener spacing: 1/2-inch lag screws or bolts staggered per Figure 19, with on-center spacing decreasing as joist span increases (e.g., 13 in o.c. at 14 ft joist span)

2Know IRC R312 guard numbers cold: 36-in minimum height when walking surface is over 30 in above grade, 4-in sphere rule for balusters, 4-3/8 in sphere at stairs, 6-in triangle at riser/tread/bottom rail, 200-lb point load

3Memorize IRC R311.7 stair geometry: 7-3/4 in max riser, 10 in min tread, 3/8 in max variation within a flight, nosing 3/4 to 1-1/4 in, handrail 34-38 in above nosing line

4Know the deck lateral load rule (IRC R507.9.2): two hold-down devices each rated for 1,500 lb, or four devices each rated 750 lb, within 24 in of each end of the deck

5Remember pressure-treated wood Use Categories: UC3B for above-ground only; UC4A required for ground contact (deck posts, ledgers, joists/beams in damp conditions)

6Identify ledger defects: no flashing under the siding lap, attachment to brick veneer (not allowed), attachment through stacked washers without continuous lag-screw embedment, missing or undersized lag screws

7Practice the hammer test on bolts: a hollow ring indicates a loose connection; a solid ring indicates tight bearing — useful when access to the back side is restricted

8Recognize ground-contact decay: probe joists and posts at grade for soft spots, look for fungal fruiting bodies (mushrooms) and black/green staining, and inspect post bases for crushing and insect damage

Frequently Asked Questions

What is the InterNACHI Certified Deck Inspector designation?

It is a credential awarded by InterNACHI (International Association of Certified Home Inspectors) to inspectors who complete the How to Perform Deck Inspections online course and pass the 25-question online final exam. The certification confirms competency in residential deck inspection: ledger attachment, footings and posts, beams and joists, decking and fasteners, guards and stairs, and identification of decay and structural defects, with content aligned to the AWC DCA-6 guide and IRC Section R507.

How many questions are on the InterNACHI Deck Inspector exam?

The final exam is 25 multiple-choice questions drawn from a larger pool of items. It is self-paced and taken online at nachi.org. Many questions reference course images. InterNACHI uses a weighted scoring system with an approximate 80% cut-off to pass — safety-critical questions are weighted more heavily for both correct and incorrect answers.

How much does the InterNACHI Deck Inspector exam cost?

The course and exam are free for active InterNACHI members. InterNACHI membership is approximately $49 per month or available at discounted annual rates. Non-members may study the course materials but typically take the exam after joining. There are no separate testing center fees because the exam is online and self-administered.

What does the InterNACHI Deck Inspector exam cover?

The exam covers: ledger attachment (lag screw/bolt spacing per DCA-6 Table 5, flashing per IRC R703.4 and R507.2.4); footings and posts (frost depth, R507.3 footing size, PT post bearing, helical piles); beams and joists (Southern Pine #2 span tables, beam-on-post hardware, joist hangers); decking and fastening (PT, composite, PVC, hardwood, hidden fasteners, gap spacing); guards and railings (IRC R312 36-in height, 4-in sphere, 200-lb point load, stair 4-3/8 in and 6-in triangle openings); stairs (R311.7 7-3/4-in riser, 10-in tread, 34-38-in handrail, graspability); and inspection methodology (hammer test, decay, corrosion, lateral movement).

Is the InterNACHI Deck Inspector credential a license?

No. The InterNACHI Certified Deck Inspector designation is a professional credential awarded by an industry association, not a government license. Most states regulate residential home inspectors (under which deck inspection falls) rather than issuing a separate deck inspector license. Verify your jurisdiction's requirements separately. Most home inspectors carry the credential as an add-on to their home inspection license.

How long does it take to prepare for the InterNACHI Deck Inspector exam?

Most candidates spend 6-12 hours on the online course and study materials before attempting the final exam. The course is self-paced and the exam can be retaken without limit. Pay particular attention to DCA-6 Table 5 lag/bolt spacing by joist span, IRC R507 footing and ledger requirements, IRC R312 guard rules (36 in, 4-in sphere, 200-lb load), and IRC R311.7 stair geometry (7-3/4 in / 10 in / 34-38 in handrail).

100+ Free InterNACHI Deck Inspector Practice Questions

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