C-9 Drywall exam questions, with answers
10 practice questions for the CSLB Drywall trade exam, each with the answer, a plain explanation and the source it rests on.
These are not real exam questions. CSLB does not release its test questions or answer keys, and nobody else has them. We write our own questions from the C-9 outline and the codes, standards and references CSLB lists for the exam. Each answer names its source so you can check it.
The C-9 exam has 5 sections. The questions below are grouped by section, with the share of the exam each one carries. Read the question, pick an answer, then open “Show the answer”. The other questions of the free test, scored section by section, are in the free 25-question C-9 test.
Planning and Estimating · 18% of the exam
Review plans and specifications; estimate project costs; evaluate material specifications.
1. A house plan calls for a Class III vapor retarder on the drywall side of the exterior walls. Under 2025 CRC Table R702.7(1), which finish is listed as a Class III retarder?
- Unperforated aluminum foil on the board
- Polyethylene sheet behind the board
- Kraft-faced fiberglass batts in the cavity
- Latex or enamel paint on the board
Show the answer
Answer: D. Table R702.7(1) puts latex or enamel paint in Class III (over 1.0 to 10 perms). Polyethylene sheet and unperforated foil are Class I (0.1 perm or less), and kraft-faced batts are Class II (over 0.1 to 1.0 perms).
2. The plans show a drywall shaft enclosure that connects three stories above grade and a basement. Under 2025 CBC 713.4, what is its minimum fire-resistance rating?
- 1 hour
- 1 1/2 hours
- 2 hours
- 3 hours
Show the answer
Answer: C. CBC 713.4 requires 2 hours for a shaft connecting four stories or more and 1 hour for fewer than four, and the story count includes basements. This shaft connects four stories, so 2 hours applies. The 1-hour answer leaves out the basement, and the code does not call for 3 hours.
Preparation, Framing, and Layout · 14% of the exam
Evaluate job site readiness; manage materials on the job site; lay out assemblies; install metal framing systems; install backing.
3. A supplier asks when to deliver the board for a new house. Per the Gypsum Association's GA-238 mold-prevention guidelines, when should gypsum board be delivered to the job site?
- Whenever the supplier's truck is free, since the board will be covered
- As soon as the framing passes inspection, so the board is ready
- A week or more before hanging, so the board can acclimate to the rooms
- As close to the time it will be hung as possible, to limit its exposure
Show the answer
Answer: D. GA-238 says gypsum board must be delivered to the job site as near to the time it will be used as possible. Board that sits on site longer has more time to pick up moisture, whether it was delivered early to acclimate, to be ready or for the supplier's convenience.
4. Exterior sheathing is already on a curtain wall of steel studs, but the interior board will not go up for weeks. Per ClarkDietrich's framing FAQs, how can the inside flanges be braced against wind in the meantime?
- Horizontal steel strapping on the interior flanges, 6 ft on center at most
- Horizontal steel strapping on the interior flanges, 10 ft on center at most
- Vertical steel strapping from track to track, 6 ft on center at most
- Diagonal wood braces nailed to the interior flanges, 4 ft on center at most
Show the answer
Answer: A. ClarkDietrich says steel strapping run horizontally on the interior flanges at a maximum of 6 ft on center, together with the exterior sheathing, braces and protects the studs until the interior board is installed. A 10-ft spacing, vertical strapping or wood braces are not what the FAQ describes.
Source: ClarkDietrich CFS FAQs, bracing requirements for curtain wall framing
Installation and Repair · 32% of the exam
Ceiling assemblies; standard wallboard assemblies; fire-rated assemblies; specialty assemblies; trims; repair of damaged drywall.
5. Your crew is hanging board on a flat, wall-to-wall Armstrong FrameAll drywall grid ceiling in a low seismic category (A or B). Per Armstrong's seismic installation sheet, what is required at the terminal ends of the grid?
- A seismic separation joint is formed where the grid meets each wall angle
- Extra perimeter wires are hung on the tees within 8 in of the wall angle
- The ends of the main beams and cross tees are screwed to the wall angle or channel
- Spacing bars or BERC clips are set on the perimeter tees and main beams
Show the answer
Answer: C. Armstrong's table requires the terminal grid ends to be screwed to the wall angle or channel in every seismic category. It lists seismic separation joints, perimeter wires within 8 in of the wall angle, and spacing bars or BERC clips as not required for this flat drywall grid.
Source: Armstrong FrameAll Drywall Grid Seismic Installation Requirements, installation conditions table
6. Your crew is hanging two layers of USG Sheetrock Flexible panels on a curved stud wall. Per USG's application tips, how are the base layer and the face layer fastened?
- Base layer: 1 5/8-in screws at 16 in o.c.; face layer: 1-in fasteners at 12 in o.c.
- Base layer: 1 5/8-in screws at 12 in o.c.; face layer: 1-in fasteners at 16 in o.c.
- Base layer: 1-in fasteners at 12 in o.c.; face layer: 1 5/8-in screws at 16 in o.c.
- Base layer: 1-in fasteners at 16 in o.c.; face layer: 1 5/8-in screws at 12 in o.c.
Show the answer
Answer: D. USG says to secure the base layer with 1-in fasteners at 16 in o.c. (at least four screws in each stud) and to space the face-layer fasteners 12 in o.c. using 1 5/8-in screws. The other choices swap the fastener length or the spacing between the layers.
Source: USG Flexible Gypsum Panels Application Tips WB2358, double-layer application
Finishing · 17% of the exam
Select and mix compounds; select the level of finish; prepare and tape surfaces; finish and coat surfaces; sand and sponge; texture surfaces.
7. Your crew will spray USG Sheetrock First Coat primer with an airless rig. Per USG's submittal sheet (J1095), how should the passes overlap and how far from the surface is the gun held to get a full coverage coat?
- Overlap each pass by 1/4 to 1/2 of the fan width, gun about 18 in from the surface
- Overlap each pass by 1/4 to 1/2 of the fan width, gun about 6 in from the surface
- Overlap each pass by 1/8 of the fan width, gun about 36 in from the surface
- Overlap each pass by 3/4 of the fan width, gun about 18 in from the surface
Show the answer
Answer: A. USG's J1095 says to overlap the preceding application with 1/4 to 1/2 of the fan width at a distance of 18 in from the surface so a full coverage coat is achieved. A smaller or larger overlap, or holding the gun much closer or farther away, is not what the sheet gives.
Source: USG First Coat Primer submittal J1095, spray application note
8. The finish schedule covers gypsum board in a plenum above the ceiling, where it will stay concealed. Per GA-214's quick reference guide, which level of finish is typically specified there?
- Level 2
- Level 1
- Level 4
- Level 3
Show the answer
Answer: B. GA-214 says Level 1 is typically specified for smoke barrier applications and areas not normally open to view, such as plenum areas above ceilings and attics. Level 2 is for tile substrates and garages, and Levels 3 and 4 are for appearance areas.
Source: GA-214-2022 Recommended Levels of Finish, Quick Reference Guide, Level 1
Safety · 19% of the exam
Personnel safety; job site safety; operating tools and equipment; work at elevated heights.
9. Your crew will clean stains in a tile area with a corrosive acid cleaner. Under Cal/OSHA Section 1512(f), what must be provided where the eyes or body of any person may be exposed to injurious or corrosive materials?
- Suitable facilities for drenching the body or flushing the eyes with clean water, readily accessible
- A first-aid kit that holds bottled eye-irrigation solution, kept in the foreman's truck on site
- A trained first-aid person who stays within sight of the work and carries bottled eyewash
- A posted list of the corrosive materials in use, with the nearest hospital's phone number
Show the answer
Answer: A. Section 1512(f) requires suitable facilities for drenching the body or flushing the eyes with clean water to be conspicuously and readily accessible wherever eyes or bodies may be exposed to injurious or corrosive materials. A kit in a truck, a posted list or a first-aid person carrying bottled eyewash does not take the place of those facilities.
Source: 8 CCR §1512(f), Cal. Code of Regulations, Title 8, §1512 Emergency Medical Services
10. A hanger finds that the trigger safety on a pneumatic stapler slows him down and wants to take it off. Under Cal/OSHA Section 1704, what applies to the tool's operating controls?
- No one may remove, tamper with, alter or otherwise disable the operating controls
- The foreman may approve altering them if the change is logged in the Code of Safe Practices
- The operator may remove them after finishing the employer's nailer safety training
- They may be altered on a light-duty stapler, because light-duty tools are exempt from the rule
Show the answer
Answer: A. Section 1704(b)(4) says operating controls shall not be removed, tampered with, altered or otherwise disabled. The light-duty exception in 1704(b)(1) applies only to the muzzle safety device, and neither training nor a foreman's approval lifts the rule.
Where to go from here
How the license works, from experience to fees: how to get a C-9 license. Everything about the course: the C-9 exam page.
Questions from our free C-9 test, written from CSLB License Examination Study Guide, Drywall (C-9), form 13E-9 (03-2026), for examinations scheduled on or after December 1, 2025. CSLB notes that the percentages are approximate. Reviewed 14 October 2026. Study guidance only; we are not affiliated with CSLB or PSI.