Drywall Contractor Exam (C-9) Questions and Correct Answers (Verified Answers) Plus Rationales 2025 Q&A | Instant Download PDF

Drywall Contractor Exam (C-9)
Questions and Correct Answers
(Verified Answers) Plus Rationales 2025
Q&A | Instant Download PDF
Question 1
What is the primary purpose of gypsum board in wall construction?
A. Structural support
B. Interior wall and ceiling finish
C. Waterproofing
D. Foundation reinforcement
Correct Answer: B. Interior wall and ceiling finish
Rationale: Gypsum board is primarily used to create smooth interior wall and
ceiling surfaces. It is not intended to provide structural support, waterproofing, or
reinforce foundations.


Question 2
Which tool is commonly used to score drywall before snapping it?
A. Tin snips
B. Utility knife
C. Chisel
D. Handsaw
Correct Answer: B. Utility knife
Rationale: A sharp utility knife is used to score the paper face of drywall, allowing
the board to snap cleanly along the scored line.

,Question 3
What is the standard thickness of drywall commonly used for interior residential
walls?
A. 1/4 inch
B. 3/8 inch
C. 1/2 inch
D. 1 inch
Correct Answer: C. 1/2 inch
Rationale: One-half-inch gypsum board is the standard thickness for most
residential interior wall applications. Thicker boards are used where greater fire
resistance or stiffness is required.


Question 4
Which fastener is most commonly used to attach drywall to wood studs?
A. Roofing nails
B. Drywall screws
C. Lag bolts
D. Masonry anchors
Correct Answer: B. Drywall screws
Rationale: Drywall screws provide excellent holding power, resist popping, and
are the preferred fastener for attaching drywall to wood framing.


Question 5
What is the purpose of drywall joint tape?
A. Increase insulation value
B. Reinforce joints between panels
C. Waterproof seams
D. Reduce drywall weight

,Correct Answer: B. Reinforce joints between panels
Rationale: Joint tape strengthens seams between drywall panels and helps
prevent cracking after joint compound is applied.


Question 6
Which joint compound is designed for the first coat over tape?
A. Finishing compound
B. Topping compound
C. All-purpose or taping compound
D. Texture compound
Correct Answer: C. All-purpose or taping compound
Rationale: Taping compound provides strong adhesion and securely embeds joint
tape during the first coat.


Question 7
What is the purpose of sanding drywall compound?
A. Increase fire resistance
B. Smooth the finished surface
C. Improve structural strength
D. Prevent moisture damage
Correct Answer: B. Smooth the finished surface
Rationale: Sanding removes imperfections and creates a smooth surface ready for
primer and paint.


Question 8
Paper-faced metal corner bead is installed primarily to:

, A. Waterproof corners
B. Protect and straighten outside corners
C. Increase insulation
D. Reduce wall thickness
Correct Answer: B. Protect and straighten outside corners
Rationale: Corner bead reinforces outside corners against impact while creating
straight, clean edges.


Question 9
The tapered edge of drywall is designed to:
A. Increase panel strength
B. Hide electrical wiring
C. Allow joint compound to create a flat seam
D. Reduce panel weight
Correct Answer: C. Allow joint compound to create a flat seam
Rationale: Tapered edges create a recessed area that accommodates tape and
compound, producing a flush finished joint.


Question 10
What is the first step before applying joint compound?
A. Prime the wall
B. Install corner bead
C. Secure the drywall panels properly
D. Sand the drywall
Correct Answer: C. Secure the drywall panels properly
Rationale: Drywall must be securely fastened before finishing begins to prevent
movement and cracking.